Cosmos Portal Blogs

The Night Sky: September 2010

The Night Sky in September 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
New Moon on the 8th Full "Harvest" Moon on the 23rd

Stars and Constellations

The Sun reaches the Autumnal Equinox on September 22 at 11:09 pm, signaling the official end of summer and the beginning of autumn in the Northern Hemisphere. The formal arrival of autumn notwithstanding, the majority of summer stars and even a few spring stars are still well placed for viewing during the early evening hours. By about 9 pm, orange-colored Artcurus in the summer constellation of Boötes (the Herdsman) is low, but still visible, in the west. The Big Dipper, which is really just a portion of the constellation Ursa Major, is low on the northwestern horizon, and so you will not be able to see it if trees or buildings obstruct your view of this part of the sky. The handle of the Dipper arcs to Arcturus.

The famous summer triangle of Vega in Lyra, Deneb in Cygnus, and Altair in Aquila is nearly overhead for a couple of hours after sunset. Orange-red Antares in the Scorpion is quite low in the southwest. You should also be able to find the asterism known as the “teapot” of Sagittarius, just east of Antares. If you are located away from city lights, you may be able to make out the Milky Way as a hazy band stretching across the sky, passing through Sagittarius, Aquila, Lyra, Cygnus, and Cassiopeia. The Milky Way is the galaxy of about 400 billion stars in which our solar system resides, and its nucleus lies in the direction of Sagittarius, but at a distance of 27,000 light years, which is far beyond the mere several hundred light years of the stars which define the constellation Sagittarius. There must be some exotic activity taking place in the core, because as early as 1931 radio engineer Karl Jansky of Bell Labs detected strong radio emissions coming from that region. Astronomers now have evidence that a supermassive black hole of several million solar masses lies at the very center of the Milky Way’s core.

As the stars of summer gradually fade into the evening twilight, the first stars of autumn are appearing in the eastern sky. Making its appearance in the southeast after about 10 pm is the white star Fomalhaut, which lies in the constellation of Pisces Austrinus (the Southern Fish). Rising due east at about this time is the Great Square of Pegasus, four whitish stars in the form of a rectangle (not quite square) lying on its edge. Low in the northeast is the famous “W” shape of the constellation Cassiopeia, the Queen of ancient Ethiopia. Note that the direction in which the “W” opens up is toward Polaris, the North Star.

Naked-Eye Planets In the Evening and Morning Sky

Since early spring, Venus has glimmered like a yellow diamond in the western sky shortly after sunset, and the spectacular evening “star” reaches its peak brightness late this month. Unfortunately, since June Venus has been setting earlier each night, and it now hovers pretty low above the western horizon at dusk. Unless your view in that direction is relatively unobstructed, Venus’s brilliance may go unnoticed. On the 1st, Venus, accompanied by the much fainter true star Spica to its right, sets about an hour and a half after sunset, or 9 pm EDT. By month’s end, Venus sets less than an hour after the Sun, but at this time a telescope will reveal an impressive crescent phase like the Moon’s. Venus will vanish entirely from the evening sky during October, only to reappear prominently in the early morning sky in November.

Mars spends September in the vicinity of Venus in Virgo. Both planets stand low in the west after sunset, but while Venus needs no optical aid to see, it will help to use binoculars to locate the much fainter Mars, which will resemble an orange star. During September, Mars sets roughly one and a half hours after sunset, or at 9 pm on the 1st and 8 pm on the 30th. Saturn, like Venus and Mars, is located in Virgo, but in the eastern portion of that constellation nearer to the Sun’s position and therefore difficult to pick out in the Sun’s glare. Saturn will vanish into the twilight by the end of September.

Jupiter reaches opposition with the Sun on the 21st, and is therefore visible all night long. Now at its closest to Earth, Jupiter sparkles like a brilliant cream-colored star in the dim constellation Pisces; it outshines everything in the night sky except for the Moon and Venus. Jupiter is a magnificent sight in a telescope, revealing cloud bands and (at the right moment) the Great Red Spot in its atmosphere and four Galilean moons surrounding the planet’s globe.

Mercury is too close to the Sun to be viewed in early September, but by midmonth Mercury begins to appear as a “morning star” low in the east at dawn. At its best, on the 19th, Mercury rises only about 90 minutes before the Sun. To spot it, one should look about a half-hour before sunrise, but it may be a challenge to spot Mercury against the bright twilight.

Information on lunar phases and rise/set times of Sun and planets is obtained from the US Naval Observatory Data Services at http://www.usno.navy.mil/astronomy/. Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

For more information on astronomy and weather, visit http://www.widener.edu/stargazing/, then click on Web Links & Resources. A set of free sky maps can be obtained at http://www.skymaps.com/

The Night Sky: September 2010

The Night Sky in September 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
New Moon on the 8th Full "Harvest" Moon on the 23rd

Stars and Constellations

Naked-Eye Planets In the Evening and Morning Sky

For more information on astronomy and weather, visit http://www.widener.edu/stargazing/, then click on Web Links & Resources. A set of free sky maps can be obtained at http://www.skymaps.com/

The Night Sky: August 2010

The Night Sky in August 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
New Moon on the 9th Full "Sturgeon" Moon on the 24th

Stars and Constellations

As night falls on clear August evenings, the first star to emerge is orange-yellow Arcturus, which stands high in the west about an hour or so after sunset. Arcturus, is an orange giant star lying 37 light years away from our solar system. This identification can be verified once it gets truly dark by first locating the Big Dipper, a part of the constellation Ursa Major, which is now dipping into the northwest. The two front stars in the bowl of the Big Dipper, Dubhe and Merak, point to Polaris, the North Star, while the arc of the Big Dipper’s handle leads to Arcturus. If the sky is dark enough, you may be able to see the Little Dipper, which is part of Ursa Minor, extending outward from Polaris toward the upper left.

One large, but faint summer constellation is Draco, the Dragon, which winds across the sky high above the Little Dipper. The Dragon’s head lies in the vicinity of Vega and its tail is near Dubhe. Draco is circumpolar for most US residents, meaning that its stars never set, but simply revolve around Polaris during the night. Draco is perhaps most notable because one of its stars, alpha Draconis, or Thuban, was the polestar some 4000 years ago, as was described in this column last August. The brightest star in Draco, gamma Draconis, or Eltamin, is an orange giant star similar to Arcturus but lying about four times farther away. Eltamin’s claim to astronomical fame is that it was used by English astronomer James Bradley in 1728 to measure a phenomenon of light known as aberration. The phenomenon has an analog in ordinary experience – as you walk through a light rainfall, the raindrops appear to be coming at you, and so you need to tilt your umbrella forward slightly. Similarly, starlight incident on planet Earth as it revolves about the Sun at a speed of 30 kilometers per second appears to be coming from a slightly different direction than it really is, and consequently, over the course of an entire year, the star itself appears to trace out a tiny elliptical path in the sky. This effect is a direct result of the finite velocity of light, and also serves as a demonstration of the Earth’s orbit about the Sun.

Try to get one last glimpse of the spring star Spica as it sets in the southwest. To the far left of Spica is orange-red Antares in Scorpius, the Scorpion, which is visible low in the south-southwest. The body of the Scorpion snakes down toward the horizon and then upward into a curved stinger. Look closely, and you will be able to see the “cat’s eyes,” Shaula and Lesath, a pair of stars located at the end of the tail which seem to be winking at you. To the upper left of the cat’s eyes is the “teapot” of Sagittarius, which marks the general direction of the core of our Milky Way galaxy. If you live away from city lights, you can make out the Milky Way as a hazy band stretching across the sky from southwest to northeast. In fact it passes through the region of the summer triangle, which at this time stands high in the east-northeast. The triangle is comprised of Vega in the constellation Lyra, Deneb in Cygnus, and Altair in Aquila. All three stars of the summer triangle are whitish in color, indicating that they are all somewhat hotter than our Sun.

Late in the evening the Great Square of Pegasus, which consists of four stars in the form of a rectangle lying on its edge, can be seen rising in the east. You should also be able to distinguish the “W” shape of Cassiopeia as it rises low in the northeast. When you see these two celestial signs, autumn is surely just around the corner!

Naked-Eye Planets In the Evening and Morning Sky

All five of the naked-eye planets are up in the evening sky this August. Mercury begins the month as an evening “star,” located low in the west at dusk. Your best bet to find it is to look about a half-hour after sunset, but be aware that you will need a western horizon unobstructed by trees or houses, and even so it will be difficult to spot Mercury against the bright evening twilight. Mercury sets about an hour after the Sun during the first week of August, and vanishes into the twilight afterwards.

In contrast to Mercury, Venus is a spectacular evening “star,” scintillating like a yellow diamond in the west at dusk. Venus actually brightens over the month of August, as the distance between it and Earth decreases. At the same time, Venus sets earlier each night: two hours after sunset, or about 10 pm EDT, at the beginning of August, but an hour and a half after the Sun by month’s end. Venus races through Virgo during August, passing Saturn on the 7th, Mars on the 18th, and the star Spica on the 31st.

Mars and Saturn begin the month of August together in the western part of Virgo, where Saturn shines like a yellow star, distinctly brighter than orange Mars, and comparable with blue-white Spica further to the east. During the course of the month, Mars continues to track eastward through Virgo, leaving Saturn behind. But Venus is moving faster than either of them, and by the end of the first week of August, the three planets are close enough to form a beautiful, though unequal, trio. During August, Mars and Saturn set, respectively, around 10 pm and 9:30 pm at midmonth. Mars will remain an evening planet (albeit a faint one) through autumn, while Saturn will vanish into the twilight by late September and reappear in the morning sky in October.

Jupiter stands out like a brilliant cream-colored star in the dim constellation Pisces, outshining everything in the night sky except the Moon and Venus. Jupiter currently lies diametrically opposite in the sky to its fellow giant planet Saturn (and also Mars and Venus), so that Jupiter rises in the east at about the same time as Saturn sets in the west, which is around 9:30 pm at midmonth. Jupiter is truly a magnificent sight in even a small telescope, revealing cloud bands and (at the right moment) the Great Red Spot in its atmosphere and four Galilean moons surrounding the planet’s globe.

Earth passes through the debris of Comet Swift-Tuttle on August 11-12, producing a meteor shower. Meteors should become visible in late evening, with the best show occurring after midnight. Look generally in the northeast direction, but meteors can be seen in any part of the sky.

Some content for this article has been obtained from the US Naval Observatory Data Services. Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

For more information on astronomy and weather, visit http://www.widener.edu/stargazing/, then click on Web Links & Resources. A set of free sky maps can be obtained at http://www.skymaps.com/

The Night Sky: July 2010

The Night Sky in July 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
New Moon on the 11th Full "Thunder" Moon on the 25th

Stars and Constellations

July evenings present significant challenges for stargazing, not only because they are often hazy but also since you have to wait until after 9 pm for the sky to become dark enough to make out the constellation patterns. As twilight fades into night, you should still be able to spot a few of the bright stars of spring before they vanish into the evening twilight. Blue-white Regulus in Leo is moving toward the western horizon and sets around 10 pm in mid-July, followed a couple of hours later by similarly colored Spica in Virgo. The brightest of the visible stars is orange Arcturus, in the constellation Boötes , which is high in the south during the early evening hours. Although it is considered a star of spring, Arcturus will remain in view until early autumn. Arcturus, Regulus, and Spica form the Spring Triangle, and July is the last month to catch a glimpse of it until it reappears in the morning sky next year.

As this trio of spring stars is setting in the west, another trio of summer stars is rising in the northeast. Making their appearance above the eastern horizon are Vega, Deneb, and Altair, located respectively in the constellations Lyra, Cygnus, and Aquila. These three stars comprise the famous Summer Triangle, which, though smaller in sky area than its spring counterpart, is more famous.

Located between the constellations Boötes and Lyra is Hercules, which is identified by its “keystone” of four stars. Perhaps the most notable star in Hercules is Ras Algethi (Arabic for the “Kneeler’s Head”), a supergiant star with a diameter of several hundred times that of the Sun and lying about 400 light years from the Sun. In 1783, English astronomer William Herschel determined, from a careful study of star motions, that our entire solar system is traveling through our Galaxy, the Milky Way, and headed toward a point in Hercules known as the apex of solar motion. Modern analyses have since shown that the apex lies closer to Vega in Lyra, but Herschel’s studies were nevertheless ground-breaking for astronomy.

Moving into view in the south-southeast in early evening is reddish Antares in the constellation Scorpius. Antares is a red supergiant and one of the largest stars known, having a diameter nearly 800 times larger than the Sun, and lying over 600 light years from our solar system. A little later in the evening, the constellation Sagittarius, with its famous “Teapot” asterism will be rising in the southeast, to the left of Antares.

Located directly above Scorpius and below Hercules is Ophiuchus, the Serpent Bearer. Its brightest star, Ras Alhague (translated as “Head of the Serpent Holder”) lies just a few degrees to the east of Ras Algethi in Hercules. Curiously, though, the most celebrated star in Ophiuchus is too faint to see with the unaided eye. That star is Barnard’s Star, a faint red dwarf discovered in 1916 by astronomer Edward Emerson Barnard at the Yerkes Observatory in Wisconsin. By comparing photographic plates taken decades apart, Barnard ascertained that the star is moving rapidly across the sky, a sure indication that it is nearby. Parallax studies have shown that Barnard’s star is 6 light years from our solar system, making it the second closest star after the Alpha Centauri triple system. Barnard’s star is also much redder and fainter than the Sun, with one-fifth its diameter, or about twice that of the planet Jupiter. Due to its swift motion across the sky, Barnard star’s will in several thousand years migrate from Ophiuchus into Hercules.

Naked-Eye Planets In the Evening and Morning Sky

Mercury begins to appear above the western horizon during July, and sets about an hour after the Sun for most of the month, but it will be quite low and difficult to spot against the bright evening twilight. Toward the end of July, Mercury passes close to Regulus, and the pair should be easily visible in binoculars. Much brighter Venus maintains its dominance in the evening sky, sparkling like a yellow gem in the west at dusk. Venus has actually been gradually increasing in brightness over the past few weeks, a trend that will continue into early autumn as Venus’s orbital motion brings it closer to Earth. But Venus will also be slowly and inexorably sinking toward the western horizon. Venus sets two and a half hours after sunset (about 11 pm EDT) at the beginning of July, but only two hours after the Sun by month’s end, at which time a telescope will reveal a nearly “quarter phase.” During the second week in July, Venus passes just above Regulus, making for a lovely sight in binoculars. The apparent proximity is, of course, a consequence of perspective, since Regulus is 15 million times farther away than Venus!

Mars, mimicking a bright orange star in the eastern part of Leo as July opens, continues its eastward motion, eventually migrating into Virgo and, at month’s end, meeting up with Saturn. Mars’s brightness has now faded to about the same as that of Regulus, which it passed close to last month. During July, Mars remains in view until late evening, setting around 11 pm at midmonth. To the east of Mars is Saturn, which resembles a bright yellow star roughly halfway between the true stars Regulus and Spica. Saturn’s brightness has diminished to where it is now comparable with that of Spica, Regulus, and Mars. At the end of July, Mars will pass just below Saturn, making for a pretty sight in binoculars or a small telescope. Saturn remains in good position for viewing during the early evening hours of July, setting around 12:30 am on the 1st and by 10:30 am on the 31st.

As Saturn and Mars are setting in the west, Jupiter is rising in the east. Jupiter, resembling a brilliant cream-colored star in the faint constellation Pisces, is second only to Venus in brightness among the planets. This July, Jupiter moves into the evening sky, rising by 11:30 pm at mid-month.

Planet Earth reaches aphelion, or its farthest distance in its elliptical orbit from the Sun, on July 6. Note that it is the tilt of Earth’s axis, not its orbital shape, which causes the changing seasons.

For more information on astronomy and weather, visit the Widener University Public Viewing Website at http://www.widener.edu/stargazing/, then click on Web Links & Resources. A set of free sky maps can be obtained at http://www.skymaps.com/

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: June 2010

The Night Sky in June 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases
New Moon on the 12thFull "Strawberry Moon" on 26th

Stars and Constellations

Although summer officially begins this month, the stars of spring are still viewable during the early evening, including blue-white Regulus in the constellation Leo. Regulus stands high in the southwest in early evening, and sets around midnight. A star with similar color and brightness is Spica, which stands about halfway up in the south shortly after nightfall. But the first true star to be spotted through the evening twilight is Arcturus, the fourth brightest star in the entire sky, in the constellation of Boötes, the Herdsman. Arcturus has a distinct yellow-orange color, and lies high above Spica in the south at around 9 pm EDT. To find Arcturus and Spica, first locate the Big Dipper, and follow the arc of the Dipper’s handle outward until you encounter Arcturus, then continue on to meet Spica.

To the east of Virgo is the next zodiac constellation Libra (the Scales). Its two brightest stars are Zubenelgenubi and Zubeneschamali, the latter of which appears to have a greenish tinge when seen through a telescope. If the sky is especially dark where you live, try to locate the semicircle of stars representing the constellation Corona Borealis (Northern Crown) just a bit above and to the east of Arcturus. In mythology, Corona Borealis represented the crown of Princess Ariadne, daughter of King Minos of Crete. The crown’s brightest star is blue-white Alphekka, also known as Gemma. To the east of Corona Borealis is Hercules, the fifth largest constellation in the sky. The brightest star in Hercules is Rasalgethi, which is both a variable star and a double star.

One of the least known spring constellations is Canes Venatici (Hunting Dogs), which passes nearly overhead in the early evening hours of June. This tiny group was originally part of Ursa Major, but in 1690 Johannes Hevelius introduced it to represent a faithful pair of dogs to accompany Boötes. Canes Venatici contains only one relatively bright star, Alpha Canum Venaticorum, better known as Cor Caroli, or "Heart of Charles." The name may have been bestowed by Edmond Halley in the late 1600s in honor of his king, Charles II. When viewed through a telescope, Cor Caroli is revealed to be a splendid double star, with the brighter component blue and the fainter one yellow. The blue star is peculiar, showing evidence of a powerful magnetic field. Cor Carolis is important enough to be listed in astronomer Dr. James Kaler’s book, The Hundred Greatest Stars (New York: Copernicus Books, 2002). The system lies about 110 light years from our solar system.

Each June the Sun passes in front of the stars of Taurus and Gemini, and so these constellations are too overwhelmed by solar glare to be seen at this time of year. The Sun reaches the solstice point on the 21st at 7:28 am, when the North Pole of Earth is tilted maximally toward the Sun, marking the beginning of summer in the Northern Hemisphere.

Naked-Eye Planets In the Evening and Morning Sky

Venus easily outshines all the other planets. It sparkles like a yellow diamond in the west-northwest during the early evening hours. Throughout June, Venus sets roughly two and a half hours after sunset, or at 11 pm EDT, which is about as late as it can set. Mars begins the month just to the west of Regulus, but it is moving steadily eastward, and passes just above Regulus on the 7th. By month’s end Mars stands well to the east of Regulus. The color contrast between the orange planet and the blue-white star is quite striking. Mars remains in view until after midnight for most of the month, setting around 1 am on the 1st and by about 11:30 pm on the 30th.

Saturn continues to inhabit the constellation Virgo near its western border with Leo. Saturn resembles a yellow star situated between the blue-white true stars Regulus to its right and Spica to its left. Both Mars and Saturn have been steadily diminishing in brightness since their respective oppositions with the Sun back in January and March, although Mars has faded more dramatically and is now slightly fainter than Saturn. Saturn remains in good position for viewing for the entire month of June, setting around 2:30 am on the 1st and by 12:30 am at month’s end.

Situated in the early morning sky, Jupiter rises by 2:30 am as June begins and around 12:30 am as the month closes. After Jupiter has cleared the horizon, it looks like an extremely bright cream-colored star hovering low in the eastern sky. Also in the morning, Mercury rises about an hour before sunrise as June begins, but it will be quite a challenge to spot it against the glare of the dawn twilight. Moreover, if your eastern horizon is obstructed by houses or trees, you will have little hope of seeing Mercury. Toward the end of the month, Mercury sinks toward the morning twilight, and reaches superior conjunction with the Sun (i.e., Mercury lies on the opposite side of the Sun from Earth) on the 28th; it will reappear in the evening sky a few days afterwards.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: May 2010

The Night Sky in May 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases
New Moon on the 13thFull "Flower Moon" on 27th

Stars and Constellations

Starlit nights in May are often pleasantly cool, with just a light jacket required for outdoor viewing. But with the Sun setting around 8 pm or later during the month, you will need to wait until close to 9 pm for the sky to get dark enough to make out the constellations. Get a last look at Aldebaran and the Pleiades star cluster, Rigel and Betelgeuse, Pollux and Castor, and Sirius and Procyon. Bright yellow Capella is setting in the northwest, but will still be visible through June. These bright stars of winter are all fading into the evening twilight, not to reappear in the night sky until autumn.

The celestial stage now belongs to the stars of spring. Regulus in Leo is high in the southeast, and another fairly bright star, Alphard, in the constellation Hydra, the Water Snake, is now rising, a bit below Regulus. If you wait until after 10 pm, you will see yet another bright star, Spica, in the constellation Virgo, rising in the southeast. The Big Dipper, which is part of the constellation Ursa Major, is now rising in the northeast, and its famous "pointer stars" point to Polaris, the North Star. The handle of the Dipper arcs to Arcturus, the bright yellow-orange star in the constellation Boötes, the Herdsman, which is rising in the east. Mizar, the second star from the end of the Big Dipper’s handle, is actually a multiple system. As a test of vision, see if you can spot Mizar’s faint companion star, Alcor.

One of the largest and most spectacular constellations in the night sky at this time of year is Centaurus (Chiron in Greek mythology) but only the uppermost portions of this group can be glimpsed from latitudes north of the Gulf Coast states. Centaurus lies just below the tail end of Hydra, and skims the southern horizon around midnight in May. Like Orion, Centaurus boasts two first-magnitude stars: alpha and beta Centauri. Alpha Centauri, also known as Rigel Kentaurus, is a triple-star system, and has the distinction of being our Sun’s nearest stellar neighbor, at a distance of 4.3 light years. Even more interesting is that the brightest of the three components, alpha Centauri A, is nearly identical in chemical composition and intrinsic brightness to the Sun. Beta Centauri, by contrast, is a blue-white giant star many times larger than the Sun and it lies much farther away than alpha, around 200 light years. If your travels take you to Mexico, Hawaii, or, even better, South America, southern Africa, Australia, or New Zealand, watch for brilliant Centaurus in the night sky in May.

Naked-Eye Planets In the Evening and Morning Sky

There is no mistaking the planet Venus, which looks like a magnificent yellow diamond hovering above the western horizon during the early evening hours of May. Throughout the entire month, Venus remains visible during the evening for a generous amount of time, setting around two and a half hours after sunset, or at about 10:15 pm EDT on the 1st and by 11 pm on the 31st.

Mars continues to shine like a bright, copper-colored star just to the west of Regulus in Leo. Mars remains in view until well after midnight, setting around 2:30 am on the 1st and by about 1 am on the 31st. Mars’ distance from Earth has more than doubled since its opposition with the Sun back in January, and its brightness has faded by nearly a factor of ten. Saturn, now located in the western part of the constellation Virgo, near the border with Leo, resembles a yellow star situated roughly between the (true) blue-white stars Regulus to its upper right and Spica to its lower left. Saturn’s brightness has faded since its opposition with the Sun back in March, and it is now about equal with that of nearby Mars. Saturn remains in good position for viewing for nearly the entire month of May, setting during the very early hours of morning.

Jupiter begins to emerge from the dawn twilight during May, rising about 4 am EDT (roughly two hours before sunrise) at the beginning of the month and by 2:30 am on the 31st. Allow Jupiter an hour or so to clear the horizon after it rises, and you will easily spot it looking like a bright cream-colored star. Mercury reached inferior conjunction with the Sun late last month, and is therefore be unobservable until very late in May, when it appears low above the eastern horizon before the Sun rises. Mercury reaches greatest elongation on the 26th, rising about an hour before sunrise, but it will be a challenge to spot it against the glare of the dawn sky.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: April 2010

The Night Sky in April 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases
New Moon on the 14thFull "Pink Moon" on the 28th

Stars and Constellations

The month of April bids farewell to many of the winter stars as they gradually disappear from view in the evening sky. Aldebaran in Taurus and the nearby Pleiades cluster are now setting in the west, and will not reappear until next autumn. Betelgeuse and Rigel in Orion are in the southwestern sky, while the twin stars Pollux and Castor in Gemini are high in the south-southwest, to Orion’s upper left. Blue-white Sirius in Canis Major and Procyon in Canis Minor also follow Orion. The yellow star Capella, in Auriga, is now high in the northwest.

While the stars of winter make their leisurely exit, the stars of spring are taking center stage. Regulus in Leo (the Lion) is high in the southeast, and another moderately bright star, Alphard, in the constellation Hydra (the Water Snake), is now rising, a bit below Regulus. Hydra is the largest of the 88 modern constellations, and represents a nine-headed monster which Hercules battled as one of his labors. The name Alphard means the “solitary one,” which makes sense because Alphard is situated in a region of the sky with almost no other nearby stars of comparable brightness. Alphard is an orange giant star, similar to Arcturus, but about five times further from our solar system, and so it appears noticeably fainter, comparable in apparent brightness to Polaris.

If you wait until after around 10 pm, you will see yet another bright star, Spica, in the constellation Virgo, rising in the southeast following the planet Saturn. The constellation Virgo is especially noteworthy telescopically because it contains over 2000 galaxies, including the famous Virgo Cluster of Galaxies, which is about 55 million light years away. Our own Milky Way and most of the galaxies in its vicinity are gravitationally bound to this cluster.

The Big Dipper, a part of the constellation Ursa Major, is now rising in the northeast, and its handle “arcs” to Arcturus, the bright yellow-orange star in the constellation Boötes (the Herdsman), which is rising in the east. Arcturus lies about 37 light years from our solar system, and has a diameter over 30 times larger than that of our Sun. Arcturus, Spica, and Regulus form a “Spring Triangle” which is larger though not as famous as its summer counterpart.

Naked-Eye Planets In the Evening and Morning Sky

Mercury is at its best in early April this year, reaching greatest evening elongation on the 8th. Look for Mercury around this date, shining like a yellow star in the west after sunset. On this date, Mercury sets about one and a half hours after sunset. Toward the end of the month, however, Mercury sinks rapidly into the western sky, getting closer to the Sun. On the 28th it reaches inferior conjunction with the Sun., and is therefore not observable.

Venus looks like a glittering yellow diamond floating above the western horizon about a half-hour after sunset, and getting higher with each passing night. As April opens, Venus sets around 9 pm EDT, or an hour and a half after sunset. By the 31st, Venus has extended its duration after sunset to just under two and a half hours, setting a little after 10 pm. During the first week of April, brilliant Venus and much fainter Mercury appear close together low in the sky at dusk.

Mars resembles a bright, copper-colored star just to the east of Pollux and Castor in Gemini. Mars stands nearly overhead during the early evening hours of April, remaining in view until well after midnight. Mars sets around 3 pm at midmonth. Mars remains quite bright during April, though it slowly fades all month. Mars has about the same brightness as the nearby star Capella on the 1st, and about the same as Betelgeuse on the 30th.

Saturn, continuing its residence in Virgo, is situated roughly between the true stars Regulus and Spica. Saturn resembles a bright yellow star as it rises above the eastern horizon in early evening. Saturn was in opposition with the Sun last month, and so it remains in fine position for viewing for the entire month of April, setting around 5 am at midmonth.

Jupiter, which was in conjunction with the Sun back in late February, is too close to the Sun to be easily seen until late April, when it sets about one and a half hours before sunrise. Look for what appears to be a bright star hovering above the eastern horizon about 45 minutes before sunrise.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: March 2010

The Night Sky in March 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases
New Moon on the 15thFull "Worm Moon" on the 28th

Stars and Constellations

Spring begins in the Northern Hemisphere on March 20^th at 1:32 pm Eastern Daylight Time, when the noon Sun stands exactly overhead at the Earth’s equator. Although not directly visible because of the Sun's daytime brilliance, the Sun begins March in the constellation (not the astrological sign) Aquarius, crosses into Pisces at mid-month, and remains in Pisces for the remainder of the month. Both Aquarius and Pisces are, of course, autumn constellations, and therefore best viewed at night at the opposite time of the year when the Sun passes through them.

The seasonal transition between winter and spring becomes apparent in the star patterns visible in the night sky as well, for the constellations of winter will over the next several weeks be fading into the evening twilight. The star Aldebaran in Taurus and the compact star cluster Pleiades, or 7 Sisters, are still on display high in the southwest. Just west of overhead is the yellow star Capella, and Betelgeuse and Rigel in Orion are high in the south-southwest. The twin stars Pollux and Castor in the constellation Gemini are high in the southeast, while the brightest appearing star in the night sky, Sirius in Canis Major, shines with bluish-white radiance to Orion’s lower left. Above and to the left of Sirius is Procyon in Canis Minor.

As evening progresses into night, the stars of spring begin to emerge from the eastern horizon. Regulus, the brightest star in Leo, stands high in the east by 9 pm, and is one of the first spring stars to become visible after dark. Regulus lies about 78 light years from our solar system, and is intrinsically 100 times brighter than the Sun. The name Regulus denotes "Royal," and, according to British astronomer Patrick Moore in his book, The Observer’s Year (London: Springer-Verlag, 1998), Regulus was one of the four Royal Stars (along with Aldebaran, Fomalhaut, and Antares) of the ancient Persian monarchy who were "Guardians of the Heavens." Regulus marks the lower part of what is Leo’s most distinctive feature: its "sickle," which represents the mane of the lion. In mythology, Leo represented the Nemean Lion which was slain as one of Hercules' 12 labors. Leo is, of course, one of the twelve zodiac constellations, with the Sun passing within its borders between August 10 and September 15. In fact, Regulus is so close to the ecliptic path that it is occasionally occulted (eclipsed) by the Moon.

But the brightest star in the spring sky is yellow-orange Arcturus in the constellation Boötes (the Herdsman), which can now be glimpsed low in the northeast. Arcturus is the 4th brightest star in the night sky and, like Regulus, is intrinsically about 100 times as luminous as the Sun. However, Arcturus lies 36 light years from our solar system, or about twice as close to us as Regulus, and so it appears brighter. The Big Dipper, which is part of the large constellation Ursa Major, is also rising in the northeast, and its handle arcs to Arcturus. The two front stars in the bowl of the Big Dipper, Merak and Dubhe, point toward the North Star, Polaris.

Naked-Eye Planets In the Evening and Morning Sky

Mercury passes through superior conjunction with the Sun on March 14th and therefore is unobservable for much of March. Toward the end of the month, however, Mercury pops up in the western sky at dusk, and by the 31st it sets nearly one and a half hours after sunset. Venus, which was in conjunction with the Sun back in January, is just beginning to emerge from the evening twilight. Venus sets only an hour after sunset as March opens, and an hour and a half after the Sun by the 31st. If there are no trees or houses to obscure the view, you may be able to spot brilliant Venus shining low above the western horizon.

Mars was closest to Earth and at its brightest back in late January, and it still outshines Saturn and nearly all the other stars in the March night sky. Mars resembles a bright, copper-colored star high in the northeast during the evening, and stays in view until the wee hours of the morning. As March begins, Mars lies about 72 million miles from Earth, which is about 10 million miles further away than it was at opposition. By month's end, the Earth-Mars distance will have grown to just over 93 million miles, or the same distance as the Sun is from Earth. Correspondingly, as March opens, Mars’s brightness has faded to one-half of what it was at opposition, and by month's end it will have dimmed to nearly one-fourth the opposition value and have the same brightness as nearby star Capella.

Saturn resembles a bright yellow star as it rises above the eastern horizon in late evening. At the beginning of March, Saturn rises by 7:30 pm, and on the 21st it reaches opposition with the Sun, rising as the Sun sets and setting as the Sun rises. Saturn is also closest to Earth this month, though still fainter than Mars. Continuing its residence in the constellation Virgo, Saturn, with its magnificent ring system, is always a wonderful sight in the telescope. Jupiter, which was in conjunction with the Sun on the last day of February, is still too close to the Sun to be observable.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: February 2010

The Night Sky in February 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases
New Moon on the 13thFull "Snow Moon" on the 28th

Stars and Constellations

February skies present a brilliant tapestry of stars that contrasts with the frigid temperatures of winter nights. The constellation Cassiopeia, which represents the throne of the Queen of ancient Ethiopia, can be seen high in the northwest, looking like the letter "M." Even higher in the northwest above Cassiopeia is Perseus, whose brightest stars form a “horn” shape which opens toward the nearby Pleiades cluster. Nearly overhead on February evenings is Auriga, the Charioteer, with the bright yellow star Capella as its "eye." Just south of Auriga is Taurus the Bull, with its bright orange star Aldebaran. Aldebaran is classed as a red giant star, and it stands in the foreground of a more distant loose cluster of stars known as the Hyades. Further to the west of the Hyades is the more famous and compact Pleiades star cluster, looking like a miniature dipper.

Following Taurus to the east is Gemini, the Twins, and its two brightest stars Pollux and Castor. Their proximity to each other is merely perspective: in reality they are about 10 light years apart. Pollux has a slight yellow or orange tinge to it, while Castor is more white in color. Remarkably, the Castor system consists of a total of six gravitationally bound stars, five of which can be seen individually in a telescope. In ancient mythology, Pollux and Castor were the offspring of the god Zeus and the mortal Queen of Sparta. Pollux was born immortal, but Castor was mortal. Both brothers were among the crew of Jason and the Argonauts. Gemini is a significant zodiac constellation because it contains the summer solstice point, which the Sun passes through on or about June 21, the first day of summer. In fact, the Sun’s apparent path around the celestial sphere (defined as the ecliptic) takes it within the boundaries of Gemini during the time interval from June 20 through July 20.

Orion the Hunter now stands high in the south, dominating the midwinter night sky. Orion's two brightest stars, Betelgeuse and Rigel, are classed, respectively, as red and blue supergiants, and are among the most luminous stars known. Orion's "sword" contains the Great Orion Nebula, a vast complex of star formation nearly 1500 light years from our solar system. Just below and to the left of Orion is the brightest star in the night sky, Sirius, in the constellation Canis Major. Sirius is one of the Sun’s nearest neighbors, at only 8.5 light years distance. Sirius is actually a binary star system, consisting of a bright primary star with a very faint companion. The companion is now known to be a white dwarf, or degenerate star, in which nuclear reactions are no longer sustained, and possessing a diameter of only 1/100 that of the Sun, or nearly the same size as planet Earth. Just a bit further to the east of Sirius is its neighbor Procyon in Canis Minor. Like Sirius, Procyon is also nearby, at 11 light years away, and also like Sirius, Procyon is a binary star system containing a white dwarf. Betelgeuse, Sirius, and Procyon comprise a "winter triangle." Though not nearly as famous as its summer counterpart, the winter triangle is nevertheless easy to pick out since the stars are bright.

After about 8 pm, you can spot some of the stars of spring mounting the sky in the east. In particular, Regulus in the constellation Leo, lies low in the east-northeast. Looking a little further northward, you may spot the Big Dipper, which is part of the constellation Ursa Major, or Big Bear, rising in the north-northeast. Seasoned skywatchers know that when they see these celestial signs spring is is just around the corner!

Naked-Eye Planets In the Evening and Morning Sky

Venus was in conjunction with the Sun last month, and is still too close to the Sun to be visible at the beginning of February. Toward the middle of the month, however, Venus begins to emerge from the evening twilight. At midmonth, Venus passes very close to Jupiter, which is sinking toward the Sun. By month’s end, Venus sets nearly an hour after sunset and, for those with an unobstructed horizon, can be seen shining low above the western horizon.

The Giant Planet, Jupiter, can still be spotted very low in the southwestern sky after sunset in early February, but not for long ; it will vanish into the evening twilight before the end of the month. Jupiter, which resembles a brilliant cream-colored star hovering above the southwestern horizon after darkness falls, has dominated the evening sky since last summer, but this month it yields the celestial stage to Mars . At the beginning of February, Jupiter sets at 7 pm, or only about an hour and a half after sunset. On the 16^th, descending Jupiter passes only a Full Moon’s width fromVenus, which is moving the opposite way. On the last day of February, Jupiter will be in conjunction with the Sun and unobservable.

As Jupiter sets into the western twilight, the Red Planet, Mars, rises in the eastern sky. Mars, which was closest to Earth and at opposition with the Sun at the end of January, now reigns supreme among planets in the night sky. Mars resembles a bright orange star in the northeast during the early evening hours, but it gets higher as the night progresses, and stays in good view until shortly before sunrise. Even a small telescope should reveal some of the surface markings and polar caps. At the beginning of the month, Mars is about as bright as Sirius, the brightest star in the night sky, which can be located just below and to the left of Orion. As Earth pulls away from Mars over the next few weeks, Mars will begin to dim in brightness, and by month’s end, Mars will have faded to about half the brightness it had when at opposition.

Saturn, now in eastern Virgo, rises by 9:30 pm at the beginning of February, and looks like a bright yellow star rising above the eastern horizon in late evening. Saturn’s yellow color contrasts with the blue-white sparkle ofVirgo’s brightest star, Spica which lies to Saturn’s lower left. By month’s end, Saturn sets around 7:30 pm, and next month will be in opposition with the Sun. Saturn is not as bright as Mars, but its fabulous ring system is worth a look through a telescope.

Mercury, which reached greatest morning elongation with the Sun on January 27^th, is still in good position for morning viewing as February opens. To spot Mercury, look for what appears to be a bright yellow star low in the south east a half-hour to an hour before sunrise. As February progresses, however, Mercury will sink into the morning twilight and be unobservable by month's end.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: January 2010

The Night Sky in January 2010

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases
New Moon on the 15thFull "Wolf Moon" on the 30th

Stars and Constellations

Frosty January evenings provide a chance to become acquainted with the brilliant stars and constellations of winter, which are now in their full splendor. At the beginning of the month, though, you can catch a last look at the Summer Triangle stars Vega, Altair, and Deneb before they vanish below the northwestern horizon during the early evening. The remaining representatives of the autumn sky, including the Great Square of Pegasus and the "water" constellations of Pisces (the Fishes) and Cetus (the Whale), will also be setting in the west later in the evening. The rest of the night belongs to the stars of winter. The constellation Perseus is nearly overhead by 8 pm, just to the east of the upside-down "W" of Cassiopeia. To the east of Perseus is Auriga, the Charioteer, one of the brightest of winter constellations. Auriga represents the Greek mythological character Erichthonius, a lame man who invented the horse-drawn chariot so he could travel about. His "eye" is the bright star Capella, which means "little she-goat." Capella is the sixth brightest star in the sky, and is actually two stars very close together.

Just south of Auriga is Taurus, the Bull, which contains the bright orange giant star Aldebaran. Aldebaran is a red giant star 25 times larger than or Sun. By coincidence, Aldebaran is situated in the foreground of the Hyades star cluster; the two are unrelated, as Aldebaran lies at a distance of 65 light years from our solar system, while the Hyades group is over twice as far away. Taurus also contains the beautiful and compact star cluster the Pleiades, or Seven Sisters, which lies 440 light years away. Taurus is an ancient constellation, which in Greek mythology represents the Minotaur, a half-man, half-bull monster. Another Greek legend states that the Taurus represents the disguise which Zeus assumed in order to seduce the Phoenician king’s daughter, Europa. Yet another story equates Taurus with the Cretan bull tamed by Hercules as one of his twelve labors.

Just east of Taurus is Gemini, which contains the stars Pollux and Castor. The most famous of all the winter constellations is Orion, the Hunter, which stands high in the south around the midnight hour during January. All of Orion’s stars, including his two brightest, orange Betelgeuse and bluish Rigel, are hundreds of light years distant from our solar system. Orion is accompanied on the hunt by his two faithful dogs, Canis Major, the Big Dog, and Canis Minor, the Little Dog , to Orion’s upper and lower left, respectively. To Canis Major belongs the brightest star in the night sky, Sirius, the "Dog Star," which looks like a brilliant bluish-white beacon in the southeast during the evening hours of early winter. Look for Sirius as it rises at 7 pm at the beginning of January, but two hours earlier, or around sunset, by month's end. Canis Minor has his own bright star, Procyon, the "Pup." In contrast to the remote stars of Orion, both Sirius and Procyon are among the Sun’s closest neighbors in space, lying at distances of only 8 and 11 light years, respectively.

Naked-Eye Planets In the Evening and Morning Sky

Jupiter, which resembles a brilliant cream-colored star low in the southwest after darkness falls, has been a faithful beacon in the evening sky since last summer. Although still an impressive sight this January, Jupiter's duration in the night sky lessens as it continues to sink toward the southwestern horizon during the course of the month. On New Year’s Day, Jupiter sets by 8:30 pm, but by the 31st, it sets at 7 pm, or only about an hour and a half after sunset. By the end of February, Jupiter will be in conjunction with the Sun and unobservable.

Mars is at its best at the end of January, when it reaches opposition with the Sun and is closest to Earth. (The last time Mars was so favorably positioned was back in December 2007.) Early in the month, Mars rises at 7:30 pm, or about two and a half hours after sunset. By the end of the month, when opposition occurs, Mars rises as the Sun sets, shortly after 5 pm, remains in view all night long, and sets as the Sun rises. Mars resembles a bright orange star low in the northeast during the early evening hours, and gets higher as the night progresses, eventually transiting the meridian high in the south at midnight. A modest telescope should reveal some of the surface markings and polar caps. It is worth noting that Mars will have about the same brightness as the brightest star in the night sky, Sirius, which can easily be located below and to the left of Orion. The color contrast between orange Mars and blue-white Sirius is striking.

Of special note is the fact that during December Mars moved eastward from Cancer into Leo, following typical west-to-east orbital behavior, but this month it shifts westward back into Cancer. This phenomenon mystified ancient astronomers, including many of the Greeks, but today it is easily explained as a result of the Earth, as it orbits the Sun, overtaking and "passing" the more slowly traveling Mars in its outer orbit, thus giving the appearance of backwards motion.

Saturn, currently located among the stars of the constellation Virgo, becomes firmly established as an evening planet this month, rising around 11:30 pm at the beginning of the month and by 9:30 pm at month’s end. Look toward the east at least an hour or so after these times to find yellow Saturn with the blue-white star Spica not far below it. While not nearly as bright as Mars, Saturn is nevertheless worth finding; a telescope or even good binoculars will reveal the famous ring system.

Mercury is in conjunction with the Sun on the 4th, and therefore is not viewable during the first week or so of January. Shortly after conjunction, however, Mercury jumps into the early morning sky, rising nearly one and a half hours before the Sun for the second half of the month. It reaches greatest elongation with the Sun on the 27th. To spot Mercury, look for what appears to be a bright yellow star low in the south east about an hour before sunrise. The other inner planet, Venus, is in conjunction with the Sun on the 11th, and remains lost in the glare of the Sun until the end of February, when it will begin to appear in the evening sky.

Earth reaches perihelion, or closest approach to the Sun, on January 2, when it will be about 3.5% closer to the Sun than it was in July. Note that it is the tilt of Earth's axis, not its orbital eccentricity, which causes the seasons.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: December 2009

The Night Sky in December 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full Moon on the 2nd and on the 31stNew Moon on the 16th

The Full Moon in December is appropriately referred to as the "Cold" Moon. It has also been called the "Full Moon before Yule." This month, there are two Full Moons, and so the second one, which falls closest to the winter solstice (when days are shortest) is designated "The Long Night Moon." The second Full Moon in any month is also often referred to as the "Blue Moon."

Stars and Constellations

The Sun reaches the southernmost position on its apparent annual path, the ecliptic, through the zodiac constellations on December 21st at 12:47 pm, thus marking the beginning of winter in the northern hemisphere. Paradoxically, the trio of stars comprising the "summer" triangle – Vega, Deneb, and Altair – is still viewable low in the western sky shortly after it gets dark. The stars of autumn dominate the early evening sky, and one of the most familiar beacons of autumn nights, the white star Fomalhaut, is now getting low in the southwest. Fomalhaut and Vega lie at approximately the same distance: 25 light years. High above Fomalhaut, also toward the southwest, is the box of four stars comprising the Great Square of Pegasus. High in the north is the constellation Cassiopeia, now looking like the letter "M." Cassiopeia is followed in the northeast by the constellation Perseus.

Located nearly overhead during the early evening hours of December are two moderately faint constellations from antiquity. One is famous, the other not. Aries, the Ram, lies just to the east of Pisces and the Great Square. Aries originally represented the first constellation of the zodiac, because two millenia ago it contained the Vernal Equinox, the point through which the Sun passes annually, marking the first day of Spring in the northern hemisphere. Due to precession, a wobble of the Earth’s axis, the Vernal Equinox has since shifted westward into neighboring Pisces. Today, the Sun passes through the constellation Aries between April 19 and May 13. In ancient mythology, Aries was the source of the Golden Fleece that was sought by Jason and the Argonauts.

Just above Aries is Triangulum, a tiny constellation (size ranking 78th out of 88) consisting of three stars in a narrow triangle. One legend says that Triangulum represents a wedding gift to Proserpina, daughter of Ceres, upon her marriage to Pluto, God of the Underworld. Triangulum is noteworthy to astronomers because it contains M33, the "Pinwheel Galaxy." M33 lies at a distance of over 2 million light years, which makes it (along with the larger and more famous Great Galaxy in Andromeda) one of the nearest spiral galaxies to our own Milky Way.

By about 9 pm, the brilliant star groups of winter can be seen rising in the east. The first star of winter to catch your eye will probably be Capella, the yellow-white star in the constellation Auriga, the Charioteer, as it ascends in the northeast. Looking high in the east, to the right of Auriga, you can find the stars of Taurus, the Bull, which contains the bright reddish star Aldebaran. Aldebaran appears to be part of a "V" shaped cluster of stars known as the Hyades. Also part of Taurus is the Pleiades, a compact star cluster shaped like a miniature dipper. Each of those apparently dim stars of the Pleiades is intrinsically several hundred times more luminous than our Sun, but appears so faint because of its immense distance of over 400 light years from our solar system. At that distance, the light from the Pleiades which you see tonight has been traveling since the days of Shakespeare and Galileo. The undisputed champion of winter constellations is Orion, which contains two very bright stars, reddish Betelgeuse and bluish-white Rigel. By midnight, Orion is high in the south, and is sure to catch your attention if you are going out for midnight service on Christmas Eve. Located in the east-northeast between Auriga and Orion are the twin stars Pollux and Castor in the constellation Gemini. Rising not far to the right of this pair is Procyon, a yellow-white star in the constellation of Canis Minor. After about 9 pm, look toward the southeast, below Rigel, and you will see the brightest star in the night sky: bluish-white Sirius, the "dog star" in the constellation Canis Major.

Naked-Eye Planets In the Evening and Morning Sky

Mercury makes an especially good appearance in the evening sky for much of this month. It reaches its greatest elongation with the Sun on the 18th, and sets nearly an hour and a half after sunset on that date. To spot it, look for what appears to be a bright yellow star low in the southwest about a half-hour to an hour after sunset. Not far from Mercury, but higher up, is the much brighter Jupiter, which remains dominant in the evening sky during December. You cannot miss Jupiter: it resembles a brilliant cream-colored star in the southwest during the early evening hours. Jupiter lies nearly on the meridian (due south) at sunset at the beginning of the month, and sets after around 10 pm. By New Year’s Eve night, it sets at 8:30 pm.

As Jupiter is setting in the southwest, Mars is rising in the opposite part of the sky. Look for a bright orange-red object low in the northeast and getting higher as the night progresses. Mars moves from Cancer into Leo this month, and continues to get brighter as the distance between it and Earth decreases. Mars rises around 9:30 pm EST at the start of December and by a little after 7:30 pm at month's end. By the pre-dawn hours, Mars will be located high above the western horizon. Note that Mars reaches opposition with the Sun (and its closest approach to Earth) late next month, and its red glow will be a beautiful sight against the cold winter night sky.

Having spent the past several months in the early morning sky, Saturn has been slowly but surely working its way into the evening sky, and this month will begin to rise before midnight. At the beginning of December, Saturn rises at about 1:30 am and on the 31th by around 11:30 pm. Look above the eastern horizon to spot yellow Saturn with the blue-white star Spica not far away. A telescope will display the famous ring system, tilted nearly edge-on. By dawn, Saturn is nearly due south on the meridian.

Venus rises less than an hour before sunrise at the beginning of December, but that time interval shrinks rapidly, so that Venus is essentially lost in the Sun's glare for most of the month. Venus will be in conjunction with the Sun in January 2010, after which it will slowly reappear in the evening sky during the spring.

The Geminid Shower is expected to reach its peak on the nights of December 13th and 14th. Meteor streaks result as Earth passes through the debris from the asteroid 3200 Phaethon. As the mostly sand-grain sized particles enter Earth’s atmosphere at enormous speeds, several tens of kilometers per second, they are incinerated by friction with the surrounding air, resulting in bright trails across the sky.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: November 2009

The Night Sky in November 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Frost" Moon on the 2ndNew Moon on the 16th

Stars and Constellations

With our clocks back on standard time in November, the sky becomes dark enough to see bright stars shortly after 5 pm. The star groups of summer are now just a memory, with one notable exception: the "summer" right triangle of Vega, Deneb, and Altair, which can still be seen high in the west. But it is the stars of autumn which reach their full spendor on November evenings. The Great Square of Pegasus, which consists of four whitish stars, is high in the south around 8 pm, while below it is the bright whitish star Fomalhaut in Pisces Austrinus (the Southern Fish). High in the northeast is the unmistakable "W" shape of the constellation Cassiopeia, followed by the constellation Perseus, which represents the hero of mythology who rode the winged horse Pegasus and rescued Andromeda from Cetus, the Whale. Cetus is the fourth largest constellation in the sky, but it contains mostly faint stars. One star which is of particular interest is Omicron Ceti, also known as Mira (meaning the Wonderful One), because it varies greatly in brightness. Mira is an enormous red giant star, nearly 350 times larger than our Sun, and it expands and contracts over a period of about 11 months.

One faint but important autumn constellation which is part of the region known as "the Sea" is Pisces, the Fishes, located between Cetus (to its lower left) and Pegasus (to its upper right). In Greek mythology, Pisces represents Aphrodite and her son Eros, who were transformed into fishes and plunged into the sea to escape from the monster Typhon. The two fishes are connected by a v-shaped pair of lines, which diverges around the Great Square of Pegasus. The lower of the two fishes, just below the Great Square, is an asterism known as the Circlet of Pisces. It consists of seven stars, but you will need a pretty clear, dark sky to see them all. Pisces is not only a zodiac constellation (meaning that the Sun passes through it during the year); it also contains the vernal equinox, the point in the sky where the Sun crosses the celestial equator moving from south to north. This occurs each year around March 20th, and marks the official start of spring. In fact, the Sun resides within the boundaries of Pisces from March 12th through April 18th of each year.

Winter begins next month, but a few winter stars can be previewed on November nights. Low in the east you can spot the reddish star Aldebaran, which is the brightest star of Taurus, the Bull. Also part of Taurus is the famous Pleiades cluster, a compact group of stars shaped like a miniature dipper. Low in the northeast to the left of Aldebaran is the bright yellow-white star Capella (meaning "little she goat"), situated in the constellation of Auriga (the Charioteer).

Naked-Eye Planets In the Evening and Morning Sky

In the evening sky, Jupiter continues to reign supreme, despite the fact that its distance from Earth has been increasing since August. Resembling a brilliant cream-colored star, Jupiter passes slowly across the southern sky during the evening hours of November, and sets a little before midnight (EST) at the start of the month. By the 30th, Jupiter sets around 10 pm. Mars, which glides through Cancer eastward to the border with Leo during November, is getting gradually brighter as its distance from Earth continues to decrease, eventually reaching its closest approach to Earth (and opposition with the Sun) in January 2010. Mars rises around 10:30 pm EST at the start of November and by around 9:30 pm at month's end.

Venus, which has adorned the early morning sky since last spring, is slowly sinking toward the Sun. It is still quite prominent, shining like a bright yellow-white star in the east-northeast during the predawn hours. As November opens, Venus rises around 5 am, and, once it has ascended a generous distance above the horizon, can be spotted a bit below the star Spica in Virgo. By month's end, Venus rises a few minutes after 6 am, or less than an hour before sunrise. Mercury reaches superior conjunction with the Sun on the 5th, and is too close to the Sun for much of this month to be of interest to the unaided eye. At the very end of November, Mercury begins to appear low in the west shortly after sunset.

Saturn, now well past its conjunction with the Sun back in September, has joined Venus as a resident of the early morning sky. Saturn rises a little before 3 am as November begins, and by about 1:30 am on the 30th. Looking east in the predawn sky, Saturn resembles a moderately bright yellow star well to the upper right of Spica.

The Leonid Meteor Shower occurs during November, and is expected to reach its peak after midnight on the 16th. Look generally toward the east where the constellation Leo will be rising, although meteors can be seen in any part of the sky.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: October 2009

The Night Sky in October 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Harvest" Moon on the 4thNew Moon on the 18th

The Harvest Moon is the Full Moon which occurs closest to the Autumnal Equinox. During most years the Harvest Moon occurs in September but this year it falls in early October.

Stars and Constellations

Cool, clear October nights provide the ideal stage for a parade of autumn constellations. The stars of late spring and summer have all but vanished from the evening sky, but one notable exception is Arcturus, the fourth-brightest star in the sky. It can be spotted as it sets low in the west-northwest, its orange-gold color a reminder of the pumpkin harvest and the leaf color of sugar maples at this time of year. Another holdover is the "summer" triangle of Vega (in Lyra), Deneb (in Cygnus), and Altair (in Aquila), which is just west of overhead by 8 pm in mid-October.

By 10 or 11 pm, the stars of autumn completely dominate the night sky. Low in the southeast is the whitish star Fomalhaut, located in Pisces Austrinus (the Southern Fish). Fomalhaut lies about 25 light years from our solar system. Further to the east is the constellation Cetus (the Whale), marked by the moderately bright star Menkar, or alpha Ceti. Menkar is a red giant star with a luminosity of over 100 suns and lying about 130 light years from our solar system. The Great Square of Pegasus, consisting of four whitish stars, is high in the south-southeast at about this same time, and is the most distinctive landmark of autumn nights. High in the northeast is the famous "W" shape of the constellation Cassiopeia, the Queen of ancient Ethiopia. The "W" opens up toward Polaris, the North Star. Between Pegasus and Cassiopeia lies the faint constellation of Andromeda, the chained maiden in Greek mythology, and just below Cassiopeia lies Perseus, the legendary hero who saved Andromeda from Cetus, the sea monster.

Lying roughly halfway between the Great Square and Fomalhaut is is the zodiac constellation Aquarius. The Sun passes through Aquarius from February 16 to March 11. Aquarius is very faint, like the two zodiac constellations it lies between: Capricornus, the Sea Goat (where the planet Jupiter currently resides) to its west and Pisces (the Fishes) to its east. This entire region of the sky, which also includes Pisces Austrinus and Cetus, is associated with water, and was even called “the Sea” by the ancient Babylonians. British astronomer Robin Kerrod writes in his book, The Book of Constellations (London: Quarto Publishing, 2002) that the Egyptians attributed the annual flooding of the NileRiver to Aquarius. In Greek mythology, Aquarius was most likely represented by Ganymede, son of the King of Tros, founder of the city of Troy.

Naked-Eye Planets In the Evening and Morning Sky

Jupiter's prominence in the evening sky seems barely diminished since its opposition with the Sun back in August. Slowly gliding across the southern sky during the evening hours of October, Jupiter resembles a brilliant cream-colored star, easily outshining everything except the Moon and Venus. Jupiter remains above the horizon until around 3 pm on the 1^st; it sets less than an hour after midnight on Halloween.

Mars, moving through Gemini and into Cancer during October, is now a little brighter than the star Aldebaran in Taurus, which lies two zodiac constellations to the west. Mars rises around 12:30 am at the beginning of October and by a few minutes before midnight on Halloween. We are just three months away from Mars’s next close encounter with Earth in late January 2010.

Venus continues to be a magnificent beacon, sparkling with a yellow-white brilliance in the east-northeast during the pre-dawn hours. Venus rises a few minutes before 5 am in early October, and at 6 am, only 1½ hours before sunrise, on the 31^st. At midmonth, Venus makes a close pairing with Saturn in the morning sky. During the closing days of 2009, Venus will vanish into the morning twilight and slowly reappear in the evening sky during early 2010. Mercury rises about an hour and a half before sunrise as October opens, and looks like a yellow star hovering low above the eastern horizon. Mercury reaches greatest elongation with the Sun on the 6^th, when it rises around 5:30 am, or 90 minutes before the Sun. Two days later, Mercury passes close to Saturn low in the predawn sky.

Saturn was in conjunction with the Sun last month, after having spent most of the spring and summer 2009 in the evening sky, and is still lost in its glare during early October. It quickly emerges from the twilight in the morning sky, however, and by midmonth it rises about 2 hours before sunrise. On the 8^th, Saturn pairs up with Mercury, and, a few days later, with Venus. By Halloween morning, Saturn is rising a little after 4 am, or about 3 hours before the Sun.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: September 2009

The Night Sky in September 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Corn" Moon on the 4thNew Moon on the 18th

Stars and Constellations

The Autumnal Equinox occurs on the 22nd of September at 5:18 pm, marking the official start of autumn in the Northern Hemisphere. On this date the durations of day and night are equal at 12 hours each, but thereafter the duration of darkness dominates until next March. Despite the formal arrival of autumn, the stars of summer are still well placed for viewing during the early evening hours. By about 9 pm, orange-colored Artcurus in the summer constellation Bootes is low, but still visible, in the west. The Big Dipper, a part of the constellation Ursa Major, is low on the northwestern horizon, and so you will not be able to see it if trees or buildings obstruct your view of this part of the sky. The handle of the Dipper "arcs" to Arcturus. Orange-red Antares in Scorpius is quite low in the southwest, and you should also be able to find the asterism known as the "teapot" of Sagittarius, just east of Antares. The constellation Sagittarius contains the nucleus or core of our own Milky Way Galaxy, which may be seen, if you are away from city lights, as a hazy band stretching across the sky.

The summer triangle of Vega in Lyra, Deneb in Cygnus, and Altair in Aquila is nearly overhead after sunset. The constellation Cygnus contains many interesting object, and one in particular is the star Albireo, also known as beta Cygni, which lies about halfway between Vega and Altair. Albireo looks like an ordinary single star to the unaided eye, but a telescope reveals it to be a double star consisting of a bright orange star (similar to Arcturus) with a blue companion star (similar to Regulus). The color contrast is quite striking when seen through even a modest telescope. Albireo is listed in University of Illinois astronomer James Kaler's book, The Hundred Greatest Stars (New York: Copernicus Books, 2002) as lying at a distance of 380 light years from our solar system. The blue star has a luminosity 100 times that of the Sun, while the orange star is a giant with an output of 700 times that of the Sun. The distance between them looks miniscule, but in reality it is about 4000 astronomical units (one astronomical unit equals the average distance between Earth and Sun). The period of each star's orbit about a common center of gravity has been estimated as about 200,000 years.

Naked-Eye Planets In the Evening and Morning Sky

As September opens, Mercury sets only about a half-hour after the Sun, and is therefore too close to the horizon to spot easily. Mercury reaches inferior conjunction with the Sun on the 20th, but shortly thereafter it swings into the morning sky. By the 30th, Mercury is rising about an hour and a half before sunrise, and looks like a yellow star hovering above the eastern horizon.

Saturn reaches conjunction with the Sun on the 17th, and is lost in its glare this month. It will reappear in the early morning sky next month. As Saturn descends into the evening twilight in the west, Jupiter ascends in the southeast. Jupiter resembles a brilliant cream-colored star, and it easily outshines everything in the night sky except the Moon and Venus, which doesn't rise until the early morning hours. A telescope or even a good pair of binoculars reveals the four large moons that Galileo discovered 400 years ago. Each of these four moons would be bright enough to see with the naked eye were it not for the overwhelming glare of parent Jupiter.

Mars, still anchored in the morning sky, is growing slowly but steadily brighter with each passing month. Mars has nearly the same brightness and color as the nearby star Aldebaran in Taurus. Mars rises around 1 am at the beginning of September and by 12:30 am at month's end. By the end of October, Mars will be rising before midnight, and by January 2010 it will be at its best as it reaches opposition with the Sun.

Venus is a spectacular sight in the pre-dawn sky. It sparkles like a yellow diamond in the east-northeast. Venus rises around 4 am in early September, and just before 5 am at month's end. On the morning of the 20th, Venus will be in conjunction with the star Regulus, the two separated by a full Moon width, making for an unusual and attractive sight

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: August 2009

The Night Sky in August 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Sturgeon" Moon on the 5thNew Moon on the 20th

Stars and Constellations

When it gets dark on August evenings, you should easily be able to locate the Big Dipper, a part of the constellation Ursa Major, which is now beginning to dip into the northwest. The two front stars in the Dipper point to Polaris, the North Star, while the "arc" of the Dipper’s handle leads to yellow-orange Arcturus, which stands high in the west. The second star from the end of the handle of the Dipper is Mizar, or zeta Ursa Majoris. As a test of your vision, see if you can spot Mizar’s faint companion star, Alcor, at less than half a moon’s diameter away. It is not known for certain if Mizar and Alcor are a truly gravitationally bound pair, but they are both at a distance of approximately 80 light years, the same as most of the other stars in the Ursa Major cluster. If the sky is dark enough, you may be able to identify the Little Dipper, which is part of Ursa Minor, extending outward from Polaris toward the upper left.

The large, but faint summer constellation Draco winds across the sky high above the Little Dipper. Draco represents the mythological dragon that guarded the golden apples in the Garden of the Hesperides. Draco is especially notable to astronomers because one of its stars, Thuban (meaning "serpent"), was the polestar some 4700 years ago, at about the time the Pyramids of Egypt were being built. Polaris is of course the polestar today, but gravitational forces from both the Sun and Moon acting on the Earth cause a slow wobble or precession of Earth’s polar axis, similar to what happens to a spinning top. The cycle of precession takes approximately 26,000 years, and its effects are to cause a change in the position of the North Celestial Pole over that period of time. Consequently, by 7500 AD, the polestar in the Northern Hemisphere will have migrated from Polaris to Alderamin in the constellation Cepheus. And in 22,400 AD, the polestar will again be Thuban. By 27,200 AD, the polestar will have come full circle back to Polaris.

Try to get one last glimpse of the spring star Spica as it sets in the southwest. To the far left of Spica is orange-red Antares in Scorpius, the Scorpion, which is visible low in the south-southwest. The body of the Scorpion snakes down toward the horizon and then upward into a curved stinger. Look closely, and you will to see the "cat’s eyes," a pair of stars located at the end of the tail. Shaula is the left and brighter of the two stars, while Lesath is the fainter one on the right. To the upper left of the cat’s eyes is the "teapot" of Sagittarius, an easy grouping to identify. The teapot marks the general direction of the core of our Milky Way galaxy. If you live away from city lights, you can make out the Milky Way as a hazy band stretching across the sky from southwest to northeast. It passes through the Summer Triangle, which at this time stands high in the east-northeast. The Triangle consists of Vega in the constellation Lyra, Deneb in Cygnus, and Altair in Aquila. All three stars are whitish in color, indicating that they are all somewhat hotter than our Sun.

By late evening, you should be able to distinguish the "W" shape of the constellation Cassiopeia as it rises low in the northeast. Also, the Great Square of Pegasus, which consists of four stars in the form of a rectangle lying on its edge, can be seen rising in the east. These are two celestial signs that autumn is not far away.

Naked-Eye Planets In the Evening and Morning Sky

Mercury sets about an hour after the Sun for most of August, and reaches greatest evening elongation with the Sun on the 24th. It looks like a yellow star hovering very low above the western horizon soon after sunset. Unless you have an unobstructed view of the western horizon, you will probably not be able to see it. At the very beginning of August, Mercury passes just above the star Regulus, a sight which can be enhanced through binoculars. Saturn looks like a white-yellow star low in the southwest shortly after sunset during August. Saturn sets at about 10 pm as August begins and a little after 8 pm by month’s end. A telescope would normally reveal the magnificent rings, but they are currently oriented nearly edge-on to our line of sight and thus are not easily detected. Saturn’s performance as an evening planet for 2009 ends this month; it reaches conjunction with the Sun in September.

While Saturn fades into the evening twilight during August, Jupiter is at its finest, reaching opposition with the Sun on the 14th. At this time, Jupiter rises when the Sun sets, around 8 pm EDT, which is a little over an hour before Saturn sets. Once it rises in the southeast, looking like a brilliant cream-colored star, Jupiter dominates the night sky until Venus rises in the early morning hours. In mid-July, a dark spot apparently from a comet or asteroid impact appeared in telescopic images of Jupiter. For more information, go to http://jupiter.samba.org/jupiter-impact.html.

Mars, situated in the morning sky, is growing slowly but steadily brighter with each passing month. Mars is about the same brightness and color as the star Aldebaran, which lies in the same constellation, Taurus, which Mars inhabits for most of August. Mars rises by around 1:30 am at midmonth. Venus is the dominant luminary in the pre-dawn sky. Once it rises it cannot be missed, sparkling like a yellow diamond in the east-northeast. Venus rises around 3 am in early August, and just before 4 am at month’s end. This is roughly two hours before morning twilight begins, and so Venus will appear especially bright against the dark night sky.

Earth passes through the debris of Comet Swift-Tuttle on August 11-12, producing a meteor shower. Meteors should become visible in late evening, with the best show occurring after midnight. Look toward the northeast, but meteors can be seen in any part of the sky.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: July 2009

The Night Sky in July 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Thunder" Moon on the 7thNew Moon on the 21st

Stars and Constellations

July evenings are not usually considered ideal for stargazing, especially in urban and suburban regions. One has to wait until well after 9 pm for the sky to become really dark, and, moreover, the atmosphere is often hazy due to the abundance of water vapor and pollutants. Nevertheless, the stars of summer are well worth the effort. Usually the first star to be spotted as twilight fades into night is orange Arcturus, located high in the south. Arcturus remains visible until it sets around 3 am at midmonth. Although usually regarded as a springtime star, Arcturus remains in good position for evening viewing until October. However, two other bright stars of spring are disappearing into the evening twilight. Blue-white Regulus in the constellation Leo is heading toward the western horizon in early evening and sets around 10 pm in mid-July. Further to the east lies Spica in Virgo. Spica has about the same color and brightness as Regulus, and it sets around midnight in the southwest.

While the spring stars are setting, the Summer Triangle, comprised of Vega in the constellation Lyra, Deneb in Cygnus, and Altair in Aquila, is rising in the east. Ascending in the south-southeast in early evening is Antares, the brightest star in the summer constellation Scorpius. The name Antares translates to mean “rival of Mars,” because of the similarity of its reddish color to that of the Red Planet. Antares is listed in University of Illinois astronomer James Kaler’s book, The Hundred Greatest Stars (New York: Copernicus Books, 2002). Antares is classed as a red supergiant, with a diameter of over 800 times that of the Sun, a visual luminosity of 12,000 suns, and lies at a distance of over 600 light years from the solar system. A moderately large telescope reveals that Antares possesses a faint companion star, Antares B, of blue (some say green) color, but which is hard to see since it lies in the glare of the much brighter Antares A. In reality, this apparently dim star has the luminosity of over two hundred Suns, but is so far away that its brightness is considerably diminished. Astronomers have determined that Antares A and B are locked in orbit about a common center of gravity in a period of 878 years.

Antares lies within a few degrees of the eclipic, the apparent path that the Sun traces out on the celestial map during the year. On around December 1st of each year, the Sun passes just north of Antares. This means that Antares is opposite to the Sun, and hence crosses the meridan at midnight (standard time) six months earlier or later, around June 1st. Three other first-magnitude stars – Aldebaran (in Taurus), Regulus, and Spica – are similarly positioned along the ecliptic at various points, with the Sun passing near to them on or about May 30, August 22, and October 17, respectively.

Scorpius is one of the oldest constellations, dating back to several centuries BC. According to one myth, Orion the Hunter boasted that he could hunt down any creature on Earth. Angered by this remark, Artemis, the goddess of the hunt, sent the Scorpion to kill Orion. The Scorpion caught up with Orion, and mortally stung him in the foot. Afterwards, the gods placed both Orion and the Scorpion in the sky, but on opposite sides to keep them apart, so that when one of the two is rising, the other is setting. As it happens, Orion contains the only other first magnitude red supergiant star in the sky – Betelgeuse. Antares and Betelegeuse are very similar. Both are massive, enormous stars, reddish in color and variable in light output. Both were once hot, luminous blue stars that bloated up into cooler red supergiants as their nuclear fuel ran out and are now in an advanced stage of evolution. Both will most likely explode in supernova within the next million or so years.

Naked-Eye Planets In the Evening and Morning Sky

Saturn’s reign as an evening planet is nearly over for 2009. Saturn sets around midnight at the start of July and at 10 pm, or less than an hour after twilight ends, by the end of July. Look for Saturn low in the southwest shortly after sunset during July. A telescope reveals that Saturn’s rings are nearly edge-on. Jupiter takes over the mantle of evening prominence from Saturn this July. At midmonth, Jupiter rises around 10 pm, which is just about an hour before Saturn sets. Even novice sky watchers will have no trouble spotting Jupiter once it rises in the southeast, looking like a brilliant cream-colored star.

In the morning sky, Mars begins the month in fairly close proximity to Venus, which lies to its lower right. Mars is far fainter than Venus, and will over the next several weeks and months be steadily pulling away from Venus, eventually making its way into the evening sky. Mars rises in the northeast at around 2 am in mid-July, and is roughly the same brightness and color as the star Aldebaran, which lies a few degrees below it toward dawn.

Venus continues its dominance among both stars and planets in the pre-dawn sky, shining like a brilliant yellow beacon in the east-northeast. Venus rises around 3 am, or nearly three hours before the Sun, for much of July. Venus is paired with much fainter Mars at the beginning of July, but the two rapidly separate as the month progresses. Mercury reached its greatest morning elongation in mid-June, and may still be visible as a yellow star low above the eastern horizon a half-hour or so before sunrise on the 1st. However, Mercury rapidly sinks into the morning twilight during early July and reaches superior conjunction with the Sun on the 13th.

Earth reaches aphelion, or farthest distance in its elliptical orbit from the Sun, on July 3rd. However, it is the tilt of the Earth's axis, not the orbital eccentricity, which causes seasons.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: June 2009

The Night Sky in June 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Strawberry" Moon on the 7thNew Moon on the 22nd

Stars and Constellations

The stars of spring remain quite prominent during June evenings, and the first star to poke through the evening twilight is Arcturus, the night sky's fourth brightest star, in the constellation of Boötes, the Herdsman. Arcturus has a distinct yellow-orange tinge, and by around 9 pm EDT lies high in the south. Also easily found is bluish-white Regulus in the constellation Leo, the Lion. Regulus stands high in the southwest in early evening, and sets around midnight. A star with nearly the same color and brightness as Regulus is Spica, in Virgo, which stands below Arcturus, about halfway up in the south shortly after nightfall. Regulus, Spica, and Arcturus form the "Spring Triangle," which, though not as famous as its summer counterpart, is nonetheless a noteworthy sight.

Later in the evening, as the stars of spring migrate toward the western horizon, the stars of summer begin to take center stage. One of the most famous of these is blue-white Vega, in the constellation Lyra, which can be seen rising in the northeast. Another is reddish Antares, in Scorpius, which is low in the southeast. In mid-June, Antares rises around 7:30 pm EDT (before sunset) and crosses the south meridian just before midnight. Lying between Virgo and Scorpius is the constellation Libra, the Balances, which contains no first magnitude stars.

Leo, Virgo, Libra, and Scorpius are all zodiac constellations, through which the Sun "appears" to pass at some time during the year. Specifically, the Sun passes through Leo from August 10 to September 15, Virgo from September 16 to October 30, Libra from October 31 to November 22, and Scorpius from November 23 to 29. These constellations are naturally best visible in the night sky at the opposite time of the year from when the Sun is located in them. Also note that these time intervals are roughly one month off from when the astrological signs of the same name are supposedly in effect, a direct result of precession of Earth’s axis over the two thousand years since ancient astrologers conjured up their pseudoscience.

It is during the month of June that the Earth, traveling in its orbit about the Sun, reaches the summer solstice point, where the Northern Hemisphere is tilted maximally toward the Sun. This event occurs in 2009 on June 21st at 1:45 am EDT, and marks the beginning of astronomical summer in the Northern Hemisphere. The Southern Hemisphere is simultaneously tilted away from the Sun, thus marking the start of winter for those folks. The politically correct designation is hence "June solstice." From an Earth-bound observer's point of view, the noon Sun appears higher in the sky at this time than at any other time of the year. For regions north of the equator, this translates into a higher concentration of solar radiation than at any other time of the year. At latitude 40 degrees North (New York, Philadelphia, Cleveland, Chicago, Des Moines, Omaha, and Salt Lake City are all close to this latitude), the duration of daylight reaches around 15 hours, while night is shortened to only about 9 hours. Consequently, the night sky does not become really dark until after about 9:30 pm Daylight Time.

Naked-Eye Planets In the Evening and Morning Sky

Saturn remains in good position for viewing during the first half of the night, setting around 2 am at the beginning of June, and at midnight by month's end. Saturn is easily spotted high in the southwest in mid-evening in the constellation Leo, resembling a bright yellow star lying to the east of Regulus, which is only slightly less bright than Saturn. Jupiter is about 25 times brighter than Saturn, and so sky watchers will have no trouble locating it once it rises. Jupiter looks like a brilliant cream-colored star in the faint constellation Capricornus, nearly on the opposite side of the sky from Saturn in Leo. As June begins, Jupiter rises around 1 am, just an hour before Saturn sets. By the end of June, Jupiter rises at 11 pm.

Mars has been a less than impressive sight thus far this year, but that will be changing in the coming months as the distance between Earth and the Red Planet continues to decrease. Mars will be moving from the morning into the evening sky late this fall, and will reach opposition with the Sun and closest approach to Earth in late January 2010. Right now, reddish Mars is a little less bright than Saturn, and can be seen above the eastern horizon during the early morning hours. Mars rises at around 3:30 am at the start of June, and by about 2:30 am at month's end. Mars passes fairly close to Venus later in the month, making for a particularly fine sight.

Venus continues to stand out as the most brilliant object (other than the Moon) in the pre-dawn sky. Venus has actually decreased in brightness over the past two months, but not by much. Venus officially reaches greatest elongation with the Sun on the 5th, but this will not be particularly noteworthy because of the unfavorable orientation of the ecliptic plane to the eastern horizon at dawn. Venus rises around 3:30 am at the beginning of June, or just about 2 hours before sunrise, and by about 3 am at the end of the month. Of note is that Venus is paired with much fainter Mars for much of June. Mercury, like Venus, reaches greatest morning elongation during June, on the 13th. For about the last 3 weeks of June, Mercury rises about an hour before sunrise, and can be seen resembling a bright yellow star hovering low above the east-northeast horizon in the morning twilight.

The nearly full Moon will pass in front of the star Antares on the night of the 6th, as viewed from much of the US, and especially along the East Coast. Disappearance/reappearance times are provided for major cities at: www.lunar-occultations.com/iota/bstar/0607antares.htm.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: May 2009

The Night Sky in May 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Flower" Moon on the 9thNew Moon on the 24th

Stars and Constellations

The nights of May are among the most delightful for observing. Not only are the nighttime temperatures pleasantly cool, with just a light jacket required, but also the air is perfumed with the scent of newly sprung blossoms of lilac and viburnum. On the other hand, you need to wait until around 8:30 pm to see the first stars come out at the beginning of the month, and until about 9 pm by month’s end. Get your last look at Aldebaran and the Pleiades star cluster, Rigel and Betelgeuse, Pollux and Castor, and Sirius and Procyon. These bright stars of winter are all fading into the twilight during early evening, not to reappear in the night sky until next autumn. Yellow Capella is setting in the northwest, but you will still be able to see it through June.

The stars of spring rule the May evening sky. Regulus in Leo (Lion) is high in the south or southeast, and another fairly bright star, Alphard, in Hydra (the Water Snake), is in the southeast, a bit below Regulus. In Greek mythology, Hydra was a multi-headed serpent which haunted the river Amymone, and was eventually slain by Hercules as one of his twelve labors. The constellation Hydra has the distinction of being the largest of all the 88 constellations. According to British astronomer Chris Kitchin, Hydra dates back to at least the time of Ptolemy’s Almagest in 145 AD, but may go back even further to the ancient Babylonians (2000 BC). If you wait until after around 10 pm, you will see yet another bright star, Spica, in the constellation Virgo, rising in the southeast. The Big Dipper, which is part of the constellation Ursa Major (Big Bear), is now rising in the northeast, and its “pointer stars” point to Polaris, the North Star. The handle of the Dipper “arcs” to Arcturus, the bright yellow-orange star in the constellation Boötes (the Herdsman), which is rising in the east. Mizar, the second star from the end of the Big Dipper’s handle is actually a multiple system To test of your visual acuity, see if you can spot Mizar’s faint companion star, Alcor.

Naked-Eye Planets In the Evening and Morning Sky

After having made an exceptionally fine appearance at the end of April, Mercury continues to be visible in the western sky after sunset, setting about 1½ hours after the Sun at the beginning of May. Mercury is moderately bright and resembles a bright yellow star hovering above the west-northwest horizon in the evening twilight. However, Mercury fades rapidly as it sinks toward the horizon during the first two weeks of May, ultimately reaching inferior conjunction with the Sun on the 18th; thereafter it moves into the morning sky. Saturn continues to be in ideal position for viewing for much of the night. It sets around 3 am at the beginning of May, and by 2 am at month’s end. Saturn continues its residence in the constellation Leo, and is easily spotted high in the south in mid-evening, resembling a bright yellow star to the east of Regulus.

Jupiter is currently a morning planet, rising in the southeast at around 3 am EDT at the beginning of May, and at about 1 am on the 31st. Jupiter is easy to spot, looking like a beautiful cream-colored star in the early morning sky. It is second only after Venus in brightness among the visible planets. Venus stands out as the most brilliant and easy to spot object (other than the Moon) in the dawn sky. It rises around 4:30 am at the beginning of May, but at about 3:30 am by the end of the month. Mars lies a bit below and to the lower left of Venus in the morning sky, and will remain an unimpressive sight until the fall. Look for Mars above the eastern horizon just before sunrise. It rises around 5 am at the beginning of May, and by 3:30 am at month’s end. Mars is still pretty faint, since it currently lies on the opposite side of the Sun from Earth.

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.

The Night Sky: April 2009

The Night Sky in April 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Egg" Moon on the 9thNew Moon on the 24th

Stars and Constellations

As April arrives, the winter stars are gradually disappearing from view in the evening sky. Now that the days have gotten longer, the bright stars and planets do not emerge from the evening twilight until around 8:30 pm. Aldebaran and the nearby Pleiades cluster in Taurus are now setting in the west, not to reappear until next autumn. Betelgeuse and Rigel in Orion are in the southwestern sky, while the twin stars Pollux and Castor in the constellation Gemini are high in the south-southwest, to Orion’s upper left. Blue-white Sirius in Canis Major and Procyon in Canis Minor also follow Orion. The yellow star Capella is still quite noticeable, high in the northwest.

While the stars of winter are making their gradual departure, the stars of spring are moving into view. Regulus in Leo is high in the southeast by 9 pm, and by 10 pm you will see yet another bright star, Spica, in the constellation Virgo, rising in the southeast. One overlooked winter-spring constellation is Cancer, the Crab, which lies between Gemini and Leo. Cancer is extremely faint, and yet it is significant because it, like Gemini and Leo, is a zodiac constellation, which means that the Sun moves through it during the year, specifically between July 21 and August 9. Two thousand years ago, the Sun entered Cancer at the summer solstice, around June 21. This explains the historical origin of the geographic term Tropic of Cancer to designate the latitude circle along which the Sun passes directly overhead on this date. Because of precession of the Earth’s axis, the Sun is now in Gemini at this time. Cancer also contains a famous cluster of stars known as Praesepe, or the Beehive, because the stars remind one of a swarm of bees around a hive. A good pair of binoculars or small telescope will reveal this beautiful cluster.

The largest of the 88 modern constellations, Hydra, the Water Snake, extends from the eastern border of Cancer to just below Spica. In mythology, Hydra represented a nine-headed monster which Hercules battled as one of his twelve labors. Cancer was a crab sent by Queen Hera to bite Hercules while he was battling Hydra, but Hercules merely stepped on the crab and crushed it. Hydra contains one fairly bright star, Alphard, which is now rising, a bit below Regulus. Just above and to the left of Hydra are two small constellations, Crater (the Cup) and Corvus (the Crow). The Big Dipper, which is part of the constellation Ursa Major, is now rising in the northeast, and its famous “pointer stars” point to Polaris, the North Star. The handle of the Dipper “arcs” to Arcturus, the bright yellow-orange star in the constellation Boötes (the Herdsman), which is rising in the east. The Dipper should be high enough now that you can spot Alcor, the faint companion to Mizar, the second star from the end of the Big Dipper’s handle.

Naked-Eye Planets In the Evening and Morning Sky

After having reached superior conjunction with the Sun on the last day of March, Mercury rises to prominence in the evening sky in April, making its finest appearance of the year. Mercury is nearly invisible at the beginning of April, but by mid-month it is setting about 1½ hours after sunset, and two hours after it for most of the remainder of April. Mercury resembles a yellow star hovering above the west-northwest horizon in the evening twilight. Mercury reaches its greatest elongation with the Sun on the 26th.

Saturn was in opposition with the Sun last month, and it continues to be in ideal position for viewing until early morning, reaching its maximum elevation above the southern horizon around 10:30 pm at midmonth. Saturn continues to reside in the constellation Leo, and is easy to spot in the east-southeast., resembling a bright yellow star lying below Regulus.

Jupiter continues to emerge slowly but steadily from the morning twilight. For much of the continental US, it rises in the southeast about 2 hours before sunrise on the 1st and about 3 hours before the Sun on the 30th. Jupiter is easy to spot, resembling a bright cream-colored star in the early morning sky. Mars continues to keep a (literally) low profile in the morning sky, hovering inconspicuously above the eastern horizon just before sunrise. Mars rises only an hour before the Sun during most of April. It will take several more months for Mars to become even modestly attractive to the eye.

After having adorned the evening sky for several months and then reached inferior conjunction with the Sun at the end of March, Venus reappears in the morning sky during April. Venus rises less than an hour before sunrise at the beginning of April, and about 1½ hours before the Sun at the end of the month. Of greatest interest is that Venus will be occulted by the thin crescent Moon on the 22nd, but unfortunately this apparition will not be visible from the East Coast of North America.

Some content for this article has been obtained from US Naval Observatory Data Services

The Night Sky: March 2009

The Night Sky in March 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Worm" Moon on the 10thNew Moon on the 26th

Stars and Constellations

The month of March marks the transition between the cold, biting nights of winter and the cool, more tolerable nights of early spring. March is also the month during which the brilliant constellations of winter evenings are gradually replaced by the more modest spring groups. During the early evening hours, the winter star Aldebaran in Taurus and the nearby Pleiades star cluster are still on display high in the southwest. Just west of overhead is the yellow star Capella, and Betelgeuse and Rigel in Orion are high in the south. The twin stars Pollux and Castor in the constellation Gemini are high in the east-southeast, while the brightest appearing star in the night sky, Sirius in Canis Major (Big Dog), shines with bluish-white radiance to Orion’s lower left. The name Sirius means "scorching." The ancient Greeks believed that Sirius was responsible for the heat of summer, since in July and August it appeared in the dawn sky just before sunrise. The hot, muggy days therefore became known as "Dog Days."

Sirius is one of the Sun’s nearest neighbors, at only 8.5 light years distance. Sirius is famous not just because it is the brightest appearing star in the sky, but because it is actually a binary star system, consisting of two components: A and B. Sirius A has about twice the diameter of our Sun, but Sirius B is a pigmy by comparison. Having a diameter of only 1/100th that of the Sun, or nearly the same size as Earth, Sirius B is classed by astronomers as a white dwarf, or degenerate star, since it is no longer is sustained by nuclear reactions. Above and to the left of Sirius is Procyon in Canis Minor (Little Dog). Procyon is also relatively nearby, only 11 light years away, and it, too, possesses a faint, white dwarf companion star.

As evening progresses into night, the stars of spring begin to emerge from the eastern horizon. Regulus, the brightest star in Leo (Lion), which stands high in the east, is one of the first spring stars to become visible after dark. Regulus lies about 78 light years from our solar system, and its name denotes "King" or "Royal." Some cultures have even associated Regulus with the birth of Christ. But the brightest star in the spring sky is yellow-orange Arcturus in the constellation Boötes (the Herdsman), which can now be glimpsed low in the northeast. Arcturus is the 4th brightest star in the night sky, after Sirius, Canopus, and alpha Centauri (Rigel Kentaurus), but the last two of these are too far south to be seen from most of the continental U.S. Arcturus is highlighted by University of Illinois astronomer Dr. James Kaler in his book, The Hundred Greatest Stars (New York: Copernicus Books, 2002), stating that Arcturus is an orange giant star with a diameter about 25 times that of the Sun and lying 37 light years from our solar system. The Big Dipper, which is part of the constellation Ursa Major (Great Bear), is also rising in the northeast, and its handle "arcs" to Arcturus. Arcturus’s name derives from "arktos," the Greek word for "bear." This is appropriate since Arcturus follows Ursa Major around the North Celestial Pole.

Naked-Eye Planets In the Evening and Morning Sky

Brilliant Venus has become a familiar sight in the southwestern sky during the early evening hours this winter, but that is about to change. Venus begins the month of March in inimitable and spectacular form, blazing like a beacon in the southwest for several hours after sunset. Even a small telescope reveals that Venus possesses a thin crescent shape, similar to the Moon. Venus sets a generous 3 hours after the Sun at the beginning of March, giving sky watchers plenty of time to take in its magnificence. As the month progresses, however, Venus rapidly descends into the evening twilight, and by the 27th Venus reaches inferior conjunction with the Sun, meaning that it is aligned between Earth and the Sun. Venus reappears in the morning sky at the end of the month, and will remain there for the duration of 2009.

Saturn reaches opposition with the Sun on the 8th, and hence is in optimal position for viewing: it rises when the Sun sets, and remains above the horizon all night long. Saturn cannot compete with Venus in terms of visual brightness, but in a telescope the view of Saturn’s rings is hard to match. Right now, the ring system is tilted nearly on edge, and so it is not as impressive as is usually the case, but nevertheless the rings are a beautiful sight. Saturn is easy to spot in the east-southeast, resembling a bright yellow star lying below Regulus in Leo.

Mars is hardly noticeable above the southeastern horizon shortly before sunrise, a situation which will not change much for another few months. Mars is nearly a year away from its next opposition, at the end of January 2010, when it will be a glorious sight in next winter’s sky, as it was back in December 2007. Mercury, like Mars, is in a poor position for morning viewing this March, rising less than an hour before sunrise at the beginning of the month. This interval only decreases as the month progresses, culminating in Mercury reaching superior conjunction with the Sun (i.e., the Sun lies between Earth and Mercury) on the 31st.

Jupiter is slowly emerging from the morning twilight after its conjunction with the Sun back in January. It rises in the southeast a little over an hour before sunrise on the 1st, and about 2 hours before sunrise on the 31st. Jupiter will return to the evening sky in superb form by late summer.

Some content for this article has been obtained from US Naval Observatory Data Services

The Night Sky: February 2009

The Night Sky in February 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Snow" Moon on the 9thNew Moon on the 24th

Stars and Constellations

During February, the winter stars and constellations seem to stare down at us with icy brilliance. Nearly overhead by 8 pm is Auriga, the Charioteer, with the bright yellow star Capella as its "eye." Just south of Auriga is Taurus, the Bull, with its bright orange star Aldebaran and the Pleiades, or Seven Sisters, star cluster. The Pleiades cluster actually contains about 500 stars, but, appropriately, only about seven are bright enough to be seen with the naked eye. The Pleiades group lies just over 400 light years away, and so we are seeing light which left the cluster when Shakespeare and Galileo were alive. Following Taurus to the east is Gemini, the Twins, and its two brightest stars Pollux and Castor. Their proximity to each other is merely perspective: in reality they are about 10 light years apart. Pollux has a slight yellow or orange tinge to it, while Castor is more white in color. Remarkably, the Castor system consists of a total of six gravitationally bound stars, five of which can be seen individually in a telescope.

The midwinter night sky is dominated by Orion, the Hunter. Standing high in the south by around 9 pm during February, Orion's two brightest stars, Betelgeuse and Rigel, form his left shoulder and right foot, respectively. Look with binoculars at Orion's "sword" and see if you notice that one of these stars is fuzzy. This object is in fact the Great Orion Nebula, a vast complex of star formation nearly 1500 light years from our solar system. Just below and to the left of Orion is Sirius, the brightest star in the sky, in Canis Major, and just a bit further to the east is its neighbor Procyon in Canis Minor. Well below Sirius is the second brightest star in the night sky, Canopus, but it never rises above the horizon for most of the United States. You would have to travel to one of the far southern states, say to Florida or south Texas, to see it.

One winter constellation that often goes unnoticed by sky watchers in the northern hemisphere is Eridanus, the River. Eridanus starts from just to the west (right) of Orion and meanders southward to below the horizon, ending with the first magnitude star Achernar. In fact, the name Achernar means "river's end" in Arabic. Achernar is not visible to observers lying north of about 30 degrees north latitude, and this includes all but the southernmost fringes of the United States. Another far less luminous member of Eridanus is the faint star epsilon Eridani. At only about 10 light years distant, it is considered one of our Sun’s interstellar neighbors. Astronomers have detected what they believe may be a Jupiter-sized planet in orbit about its otherwise unremarkable parent star.

Looking toward the east-northeast after about 8 pm, you should be able to spot the star Regulus in the constellation Leo, rising above the horizon. Further to the left, the Big Dipper, a part of the constellation Ursa Major, or Big Bear, is rising in the north-northeast. These are the celestial signs that spring is is just around the corner!

Naked-Eye Planets In the Evening and Morning Sky

Over the past several months, Venus has been a dazzling sight in the southwestern sky during the early evening hours, and its spectacular display will continue through February. Venus blazes like a brilliant yellow star in the southwest for several hours after sunset, reaching its maximum brightness during the latter part of the month. At the beginning of February, Venus sets about 4 hours after the Sun, but this interval decreases to 3 hours by the end of the month, a sign that Venus will soon be departing from the evening sky. Indeed, it does so next month. Saturn is nowhere near as bright as Venus, but it is still easy to spot in the east-southeast below Regulus during the late evening. Saturn rises around 8:30 pm EST on the 1^st and by 6:30 pm at month’s end. Around midnight, Saturn is easily located, resembling a bright yellow star roughly halfway between the first-magnitude stars Regulus and Spica.

Mercury, Mars, and Jupiter are all located in the morning sky during February, and all are difficult to find. Mercury reaches its greatest morning elongation with the Sun on the 14^th, when it rises a little over one hour before sunrise. It resembles a bright yellow star. Nevertheless, an unobstructed southeastern horizon will be needed to locate it. Toward the end of February, Mercury aligns closely with Mars and Jupiter in the dawn sky. Mars was in conjunction with the Sun back in December, and it is still too close to the Sun to be seen during much of February. On the 28^th, Mars and Mercury may be spotted together just above the southeastern horizon shortly before sunrise. Jupiter was in conjunction with the Sun last month, and will remain lost in the glare of morning twilight until nearly the end of February, when all three morning planets cluster together very low above the southeastern horizon just before sunup.

Some content for this article has been obtained from US Naval Observatory Data Services

14th Issue of Astronomy Education Review Now Available

AMERICAN ASTRONOMICAL SOCIETY IS NEW PUBLISHER.

Astronomy Education Review (AER), the web-based journal/magazine
about astronomy education and outreach, announces the on-line
publication of its 14th issue, now complete on the Web at
http://aer.noao.edu. There is no charge for reading or downloading
the full articles in the journal.

The table of contents is below.

We are proud to announce that, as of January 2009, the American
Astronomical Society has taken over the publication and management
of the journal.

The new web site, on which most back issues are already on display
and on which all issues and new papers will be available by mid-February,
is: http://aer.aip.org.

We will keep all issues through No. 14 live at aer.noao.edu for several
months. However, please begin to substitute the new address in any
links or bookmarks you have for the journal.

AER actively solicits interesting papers and articles on all aspects of
astronomy and space science education and outreach. All papers are
refereed, and a set of guidelines for contributing to AER is available
at http://aer.aip.org. These guidelines are slightly different from
the previous ones, so be sure to check the new web site if you are
planning to submit a paper.

Manuscripts and questions can be directed to:
aer@aas.org.

Sidney Wolff and Andrew Fraknoi, Editors

________________________________________

Papers and articles in the current issue include:
________________________________________

Development and Application of a Situated Apprenticeship Approach to Professional Development of Astronomy Instructors -- Edward Prather & Gina Brissenden (U. of Arizona)

How Do Pre-service Teachers' Religious Beliefs Affect Their Understanding of Astronomy? -- Jesus Rodrigo F. Torres (Rizal Technological U., Philippines)

Impact of Modifying Activity-Based Instructional Materials for Special Needs Students in Middle School Astronomy -- Julia Olsen & Timothy Slater (U. of Wyoming)

Regulations and Ethical Considerations for Astronomy Education Research: A Suggested Code of Ethics -- Erik Brogt, Erin Dokter, Sanlyn Buxner, & Jessie Antonellis (U. of Arizona) and Tom Foster (S. Illinois U.)

Effect of Night Laboratories on Learning Objectives for a Non-major Astronomy Class -- Ian C. Jacobi (Rensselaer Polytechnic Inst), et al.

Virtual Field Trips: Using Google Maps to Support Online Learning and Teaching of the History of Astronomy -- Christopher Fluke (Swinburne U. of Technology)

Online Academic Integrity -- Kendra Sibbernsen (Metropolitan Community Coll.)

Grade 9 Astronomy Study: Interests of Boys and Girls Studying Astronomy at Fletcher's Meadow Secondary School -- Mirjan Krstovic, et al.

A Special Section on Demonstrations for Teaching Astronomy:

An Interactive Demonstration of Solar and Lunar Eclipses -- Joanne Rosvick (Thompson Rivers U.)

A Student-Constructed Three-Dimensional Model of Stars in Nearby Space -- Tracy Furutani (N. Seattle Community Coll.)

Demonstrations Illustrating the Difficulties Astronomers Face When Observing Astronomical Objects -- Jeff Stanger (Sydney Girls H.S. & Sydney Obs.)

A Doppler Shift Speed Gun -- Reid Sherman (U. of Chicago)

Demonstrating Absorption Spectra Using Commercially Available Incandescent Light Bulbs -- Jennifer Birriel (Morehead State U.)

Kinesthetic Life Cycle of Stars -- Erika Reinfeld (Harvard-Smithsonian CfA) & Mark Hartman (MIT Kavli Inst.)

The Milky Way Model -- Robert Bryan Friedman (U. of Chicago)

plus a book review, announcements, and more

================================
Andrew Fraknoi, Chair, Astronomy Program
Foothill College, 12345 El Monte Rd.,
Los Altos Hills, CA 94022, USA

Telephone: (650) 949-7288
E-mail: fraknoiandrew@fhda.edu
================================

The Night Sky: January 2009

The Night Sky in January 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Wolf" Moon on the 11thNew Moon on the 26th

Stars and Constellations

The clear, cold nights in January offer great rewards for braving the frigid conditions. A few autumn stars are still visible, including those belonging to Cetus, the Whale, and the four stars which comprise the Great Square of Pegasus, which are now setting in the west. But the rest of the evening is ruled by the brilliant stars of winter. The constellation Perseus is nearly overhead by 8 pm, just to the east of the upside down “W” of Cassiopeia. To the east of Perseus is Auriga, the Charioteer, whose eye is the bright yellow star Capella. The name Capella is derived from Latin, and means “little she-goat,” a likely reference to the mythological goat that suckled the baby Zeus. Capella is 42 light years away from our solar system and, although it appears as a single object to the eye, astronomers have deduced that it really consists of two stars, each of which is a giant over 10 times bigger in diameter than our Sun. Just south of Auriga is Taurus the Bull, a zodiac constellation. Taurus contains not only the bright orange star Aldebaran but also the compact star cluster the Pleiades, or the Seven Sisters. Just east of Taurus is another zodiac group, Gemini, which contains the “twin” stars Pollux and Castor.

By far the most brilliant of all the winter constellations is Orion, the Hunter, which stands high in the south around the midnight hour during January. Orion is a veritable jewel box of relatively young stars, most of which lie hundreds or even thousands of light years from our solar system. These include the four stars which outline his major perimeter (listed clockwise from the upper left): Betelgeuse (pronounced beetle-juice), Bellatrix, Rigel, and Saiph. Betelgeuse is a red supergiant, similar to the summer sky's Antares in Scorpius. The other three are blue supergiants or giants. Cutting across Orion’s middle is his belt, a very distinct line of three bluish-white stars, Alnitak, Alnilam, and Mintaka. Alnitak and Alnilam lie over 1000 light years from our solar system and Mintaka is over 2000 light years distant. Extending downward from Orion’s belt is his sword, which contains the Orion Nebula, officially designated as Messier 42, a birthblace for thousands of new stars. It lies at a distance of 1500 light years.

Two faithful dogs, Canis Major, the Big Dog, and Canis Minor, the Little Dog , are found to Orion’s upper and lower left, respectively. Canis Major contains the brightest appearing star in the sky, Sirius, which looks like a brilliant bluish-white beacon in the southeast during the evening hours of early winter. Canis Minor has his own bright star, Procyon, the “Pup.” Sirius and Procyon are among the Sun’s nearest neighbors in space, lying at distances of only 8 and 11 light years, respectively.

Naked-Eye Planets In the Evening and Morning Sky

Jupiter, which was such a glorious sight in the evening sky last summer, can still be spotted low above the southwestern horizon after sunset, but not for long. After about the first week of January, it vanishes into the twilight. Before it bids (temporary) farewell to the evening sky, Jupiter pairs up with Mercury on New Year’s Day, when the two planets pass close to each other in the sky. Jupiter reaches conjunction with the Sun on the 24^th, and will slowly reappear in the morning sky during February. Mercury begins January in close proximity to brighter Jupiter, low in the southwestern sky at dusk, so you will need to have a clear view of the horizon to see them. Mercury reaches its greatest evening elongation with the Sun on the 4^th, but thereafter it descends rapidly toward the Sun. Mercury passes between the Earth and Sun (inferior conjunction) on the 20^th, after which it moves into the dawn sky.

Among the planets visible this month, Venus takes pride of place, blazing like a brilliant yellow star in the southwest during the early evening hours. Venus reaches its greatest evening elongation with the Sun on the 14^th, and sets nearly 4 hours after sunset all month (around 9 pm for much of the continental US), giving observers plenty of time to see it. A telescope reveals that Venus is half-illuminated, or at “quarter phase.” Around the 22^nd, Venus passes close (apparently) to the faint planet Uranus, making for an interesting sight in binoculars or a small telescope.

Saturn, which now lies in the constellation Leo on the border with Virgo, appears in late evening, rising around 10:30 pm EST on New Year’s Day and by 8:30 pm at month’s end. Once it is well up, Saturn is easily located, resembling a bright yellow star high in the east-southeast, roughly halfway between first-magnitude stars Regulus and Spica. Saturn’s system of rings is currently tilted nearly on edge, and so it will not be very prominent in a telescope.

Mars, which was in conjunction with the Sun last month, is still too close to the Sun to be viewed, but should begin to reappear faintly in the pre-dawn sky by the end of February. Mars will eventually work its way back to the evening sky in late 2009, and by January 2010, one year from now, Mars will return to glorious form when it makes its closest approach to Earth since December 2007.

Earth reaches perihelion, or closest approach to the Sun, on January 3, when it will be about 3.5% closer to the Sun than it was in July. Note that it is not this effect, which results directly from the eccentricity of Earth’s orbit, but rather the tilt of Earth’s axis, which causes seasonal variations.

The Quadrantid meteor shower should peak on or around January 3. The meteors appear as Earth speeds through the debris trail left behind by an object known as 2003 EH1, probably a comet fragment. The particles burn up as they enter Earth’s atmosphere, creating luminous streaks.

Some content for this article has been obtained from US Naval Observatory Data Services

Notes From the Astronomy Underground: What REALLY happens at Colloquia

...as inspired by my Article Writing Class. If you ever wondered what goes on behind closed doors up in that Ivory Tower, what actually runs through the minds of some of the evidently brightest left cranial hemispheres on the planet (or at the very least in central PA), your curiosities will now be quenched.

Do curiosities get thirsty? I guess so. Let's go with that.

And now, in grisly detail, I present:

My Concentration During Department Colloquia

Gorge on free pre-colloquium coffee and cookies like some kind of bitter, sleep-deprived graduate shark whose waters have been chummed with empty calories and caffeine.
Speaker makes some kind of remotely amusing topical joke.
Realize that the presentation has absolutely nothing to do with research interests and will be about as enthralling as watching the history of astroturf on Modern Marvels. Stew in indignation of sitting in a location unsuitable for an inconspicuous exit.
Wonder why newspapers still print The Family Circus, even if everyone I can think of hates it and all its nauseatingly smarmy, malapropism-spewing self-righteousness...
Crap. Did I miss something important? No, he's still discussing the outline of the talk. Like he's been doing for the last 20 minutes.
Get distracted by something shiny. Usually, it's the speaker's increasingly sweaty bald spot.
Professor rudely interrupts with a thinly veiled attempt to sell his own research accomplishments while callously dismissing the speaker's.
Blood sugar spike
Get lost in a dizzying orgy of crowded, low-resolution graphs and nonsensical hieroglyphs that pass as equations. Should have been paying attention... is n_M the mass function or the number density? And what the hell is "enthalpy?" Sounds like an '80s hair band.
Fantasize about feeding Sarah Palin into a wood chipper.
Look at all these undergrads at rapt attention, so young, so full of energy. Sickening. No, don't even... put that hand down! Don't even think about... great, you're asking a question. Just for the sake of asking a question. Awesome. Yeah, we're all impressed with you now.
What was the name of that actress on Mork and Mindy? Dammit, this is really gonna bother me...
Another faculty member rips into the speaker and they verbally spar in that clumsy, stilted way that academics do. Jesus, it's like watching chickens peck at each other over prime spots at a feed lot.
Wonder if it's possible to make a miniature house out of bacon. Like a gingerbread house, but made from a heaping pile of nitrates and pig fat instead of processed sugar and Americana.
Diabetic coma from sugar/caffeine crash
People are applauding. Rouse from slumber like an irritable, tranquilized bear.

The Night Sky: December 2008

The Night Sky in December 2008

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
"Full Moon before Yule" on the 12thNew Moon on the 27th

Stars and Constellations

The Sun’s apparent annual path in the sky (an effect of perspective created as Earth orbits about the Sun) takes it through the Ophiuchus/Sagittarius region during December, coinciding approximately with the celebrations of Christmas and Hanukkah. On December 21^st at 7:04 am EST, the Sun reaches its southernmost position in Sagittarius, marking the official beginning of winter in the Northern Hemisphere and summer in the Southern Hemisphere. At this time of year, the Northern Cross, known officially as the constellation Cygnus, stands upright on the northwestern horizon in early evening, with its bright star Deneb shining at the top of the cross. Somewhat below Deneb lies the even brighter Vega, still visible low in the western sky. Fomalhaut, the white jewel of autumn, is now getting low in the southwest. High in the southwest are the four stars comprising the Great Square of Pegasus. High in the north, the constellation Cassiopeia is now looking like the letter “M”, and is followed in the northeast by the constellation Perseus. The most famous star in Perseus is Algol, known as the “Demon Star” in medieval Arabic culture, because it frequently seemed to “wink.” Modern astronomers have found that Algol actually consists of two stars which eclipse each other in their mutual orbit over a cycle of 3 days , thus creating periodic changes in brightness (the winking).

By 9 or 10 pm, the brilliant star groups of winter move into fine position for viewing. Capella, the yellow-white star in the constellation Auriga, the Charioteer, is ascending in the northeast. High in the east, to the right of Auriga, is Taurus, the Bull, which contains the bright orange-red star Aldebaran. Also part of Taurus is the compact Pleiades star cluster, or Seven Sisters. Dominating the winter night sky is the constellation Orion, the Hunter, with its two very bright stars, reddish Betelgeuse and bluish-white Rigel. Most of Orion’s stars are hundreds of light years from our solar system. Just below Orion is the constellation Lepus, the Hare. This faint and often overlooked group contains the variable star R Leporis, which is listed in University of Illinois astronomer James Kaler’s book, The Hundred Greatest Stars (New York: Copernicus Books, 2002) as the reddest naked-eye star in the sky. Also known as Hind’s Crimson Star after the 19^th century astronomer who discovered it, R Leporis is a pulsating giant star with a diameter of over 300 times that of the Sun. Its deep red color is due to its unusually cool temperature (for a star) and also to the fact that its atmosphere contains carbon molecules which absorb a significant amount of the blue light.

Located in the east-northeast between Auriga and Orion is the constellation Gemini, which contains the “twin” stars Pollux and Castor. After about 9 pm, the brightest star in the night sky emerges in the southeast, below Rigel. This is blue-white Sirius, the “dog star” of the constellation Canis Major.

Naked-Eye Planets In the Evening and Morning Sky

Venus is magnificent in the sky at dusk, mimicking a brilliant yellow star above the southwestern horizon. Over the past few months, Venus has gotten higher and brighter in the evening sky, and that trend will continue throughout December. Venus sets about 3 hours after the Sun in early December, but just shy of 4 hours after it on New Year’s Eve. As a visual bonus, Venus passes close to Jupiter during the first few days of December, and the duo of bright planets makes for a remarkable spectacle in the sky at dusk.

Jupiter’s days as an evening attraction may be numbered, but the Giant Planet still garners attention, especially since it is paired with even more brilliant Venus in early December. They both reside low above the southwestern horizon at dusk. While Venus increases its separation from the Sun during December, Jupiter continues to sink toward the evening twilight. Jupiter sets around 7:30 pm at the beginning of December, but a little after 6:00 pm, or only about 1½ hours after sunset, by NewYear’s Eve. On that date, Mercury passes very close to Jupiter to produce another eye-catching pairing.

Mercury is invisible at the beginning of the month, lost in the glare of the Sun. It rapidly ascends into the evening sky, however, and by New Year’s Eve, it sets 1½ hours after the Sun. Assuming you have clear view of the western horizon, spotting Mercury on this date should be easy: Mercury looks like a modestly bright yellow star sitting just to the left of much brighter Jupiter.

Saturn migrates from the morning sky into the late evening sky during December, rising around 12:30 am EST in early December, and by 10:30 pm at month’s end. Saturn is easily picked out as it rises in the east, resembling a bright yellow star in the constellation Leo below the true bluish-white star Regulus.

Saturn appears less bright than usual, however, because the normally bright but thin ring system is currently seen nearly edge-on (as even a small telescope will reveal), and thus they will add little to Saturn’s magnitude in the night sky.

Last year in December Mars reached opposition with the Sun and was therefore in prime position for evening viewing. Mars was also closest to Earth, with a brightness rivaling that of Jupiter. This December, by contrast, Mars is on the far side of its orbit from Earth, reaching conjunction with the Sun in on the 5^th. It is thus is not viewable at all. Mars will very gradually re-appear in the morning sky during winter/spring of 2009, but eager Mars watchers will need to wait until late 2009/early 2010 to see Mars regain its former glorious stature in the evening sky.

The Geminid Meteor Shower is expected to reach its peak on the nights of December 13 and 14, as the Earth in its orbit passes through debris shed by the asteroid 3200 Phaethon. The trails appear to radiate from the constellation Gemini, but they can be seen in nearly any part of the sky. This year a just-past-full Moon will wash out the sky contrast, allowing only the brighter meteors to be seen.

Some content for this article has been obtained from US Naval Observatory Data Services

The Night Sky: November 2008

The Night Sky in November 2008

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Frost" Moon on the 13thNew Moon on the 27th

Stars and Constellations
The stars of autumn are in full spendor on November evenings. With our clocks moving back to Standard Time at the beginning of November, the sky becomes dark shortly after 5 pm. We can still catch the “summer” right triangle of Vega, Deneb, and Altair high in the west after dusk. The Great Square of Pegasus, which consists of four whitish stars, is high in the south by around 8 pm, while below it is the bright whitish star Fomalhaut in Pisces Austrinus (the Southern Fish). High in the northeast is the familiar “W” shape of the constellation Cassiopeia. Following Cassiopeia is the constellation Perseus, which represents the hero of mythology who rode the winged horse Pegasus and rescued Andromeda from Cetus, the Sea Monster (the Whale in modern times).

The constellations of Andromeda and Cetus are both relatively faint, but Andromeda contains within its borders M31, otherwise known as the Great Galaxy in Andromeda. M31 can actually be seen as a fuzzy patch with the unaided eye in locations far from light pollution. The “M” stands for Charles Messier (1730-1817), a French astronomer of the 18th century who searched the sky for comets, which like planets, travel in orbits about the Sun. The objects in Messier’s list look fuzzy, like comets, but in reality are mostly distant nebulae and star clusters. Messier compiled his list of “M” objects so that other comet hunters would not waste their time investigating these objects. The Andromeda Galaxy lies about 2½ million light years from our own galaxy, the Milky Way, and is very similar in structure but even larger in size.

A few stars of winter can be previewed on November nights. Low in the northeast is the bright yellow-white star Capella (meaning “little she goat”), situated in the constellation of Auriga (the Charioteer). Capella is often the first of the winter stars to make its appearance. If you stay up late, Capella will pass nearly overhead around 1 am in mid-November. By February, Capella will be located nearly overhead during the evening hours. Low in the east you can find the stars of Taurus, the Bull, which contains the bright reddish star Aldebaran. Aldebaran appears to be part of a “V” shaped cluster of stars known as the Hyades. Even more famous is the Pleiades cluster in Taurus, a compact group of stars shaped like a miniature dipper lying somewhat above Aldebaren.

Naked-Eye Planets In the Evening and Morning Sky

Venus is unmistakable in the evening sky at dusk, shining like a brilliant yellow star above the southwestern horizon. Venus continues to get higher and brighter in the evening sky, setting about 2 hours after the Sun at the beginning of November, but nearly 3 hours after it at month’s close. Venus begins the month near Antares in Scorpius, but moves rapidly through Ophiuchus and into Sagittarius during November. At the very end of November, Venus will pass very close (apparently, of course) to Jupiter, making for a spectacular sight in the sky shortly after sunset.

Jupiter continues to be a delightful presence during the early evening hours of November, resembling a brilliant cream-colored star as it slowly drifts toward the southwestern horizon. Jupiter resides, as it has for the past several months, within the constellation Sagittarius, positioned above the famous “teapot” asterism. At the beginning of November Jupiter lies low in the southwest at dusk , and sets around 10 pm EST. By the 30th, Jupiter sets around 7:30 pm, only about 2½ hours after sunset. Most notably, however, is that by month’s end, Venus and Jupiter will pair up in Sagittarius, with Venus being the brighter of the two. This will certainly present a beautiful spectacle of two “jewels” during the early evening hours.

In the morning sky, Saturn continues to improve its visibility, rising around 2 am EST in early November, and by 12:30 am around month’s end. Saturn is easily picked out high in the south just before dawn, resembling a bright yellow star in the constellation Leo.

Mercury begins the month of November rising about an hour before the Sun, but you will need a very low horizon to see it. It looks like a modestly bright yellow star hovering low in the southeast before dawn. Mercury gradually vanishes into the morning twilight during the course of the month, eventually reaching superior conjunction with the Sun (i.e., aligned with the Sun on the far side from Earth) on the 25th.

Mars is too closely aligned with the Sun this month to be viewed, and it will continue its leave of absence from the night sky for several months. Mars reaches conjunction with the Sun in early December, and will eventually re-appear in the morning sky in early 2009.

The Leonid Meteor Shower is expected to reach its peak after midnight on November 17th. Look generally toward the east where the constellation Leo will be rising, although meteors can be seen in any part of the sky. The meteors are the incandescent trails produced by fragments of Comet 55P/Tempel-Tuttle entering Earth’s atmosphere at supersonic velocities.

Some content for this article has been obtained from US Naval Observatory Data Services

13th Issue of Astronomy Education Review now available

Astronomy Education Review (AER), the web-based journal/magazine about astronomy education and outreach, announces the on-line publication of its 13th issue, now complete on the Web at http://aer.noao.edu. There is no charge for reading or downloading the full articles in the journal.

The table of contents is below.

When you go to the AER site, you will see that the next issue is already under way. You can find the full 13th issue by clicking on back issues and then on vol. 7, no. 1.

AER actively solicits interesting papers and articles on all aspects of astronomy space science education and outreach. The journal gets between 130,000 and 270,000 hits per month from every state of the U.S. and over 90 other countries. All papers are refereed and a set of guidelines for contributing to AER is available on the web site.

We are also delighted to announce that, as of 2009, AER will become a journal of the American Astronomical Society. The transition should be seamless and we continue to accept papers and announcement for publication in either the last issue of 2008 or the first issue of 2009. More information about the change of publishers will be available in the months to come.

Sidney Wolff and Andrew Fraknoi, Editors

________________________________________

Papers and articles in the current issue include:
________________________________________

* "The First Big Wave of Astronomy Education Research Dissertations and Some Directions for Future Research Efforts" by Timothy Slater, University of Wyoming

* "Development and Implementation of a Lab Course for Introductory Astronomy" by Nate McCrady and Emily Rice, UCLA

* "What Are They Talking About? Lessons Learned from a Study of Peer Instruction" by Mark James, Federica Barbieri, and Paula Garcia, Northern Arizona University

* "An International Asteroid Search Campaign" by J. Patrick Miller, Hardin-Simmons University, et al.

* "Images on the Web for Astronomy Teaching: Image Repositories" by Andrew Fraknoi, Foothill College

* "The Interactive Astronomy Textbook" by Christopher Fluke and David Barnes, Swinburne University of Technology

* "Distance to the Center of the Milky Way Galaxy: An Experiment for Intermediate-Level Students Using Research Data and Professional Analysis Tools" by M. T. Fitzgerald, Monash University, et al.

* "The Seasons Explained by Refutational Modeling Activities for Pre-service Teachers" by Valérie Frede, Paris Observatory

* "Astronomy@Home" by George Mumford, Tufts University

* "Good Reading from Other Sources on Astronomy Education and Outreach (Published in 2007)"

plus other papers, a book review, announcements, and more

Notes from the Astronomy Underground- Astropalooza

According to the tagline in Ridley Scott’s 1979 blockbuster Alien, “In space, no one can hear you scream.” It’s true that sound waves, unlike light, need a medium- some kind of substance to carry their energy across a distance. And space is a vacuum, which, save the occasional solar system, fuzzy nebula, or bizarre stellar end product, is devoid of any respectable amount of matter. No matter, no sound, right?

Well, almost. Space is not completely empty. There are about one or two hydrogen molecules per square centimeter in the sparsest of regions. It beats our clumsy, terrestrial vacuum chambers handedly, but it’s not a vacuum in the strictest connotation of the word. Sound waves can still propagate through space, but so slowly and ineffectively that it would be pointless for aerophilic humans to do anything about it. Unless of course, we had ears many millions of times larger than we do now, and could hear frequencies millions of billions of times lower (and slower) than our current 20 Hz limit. Only then could we collect enough sluggishly disturbed atoms that listening to the cosmos would be feasible.

Given that sound is not the exclusive domain of terrestrial existence, how might we tune into this ambient “flicker noise,” nature’s otherwise inaudible music? Scientists have come up with a couple of different ways to observe the instruments of the cosmic orchestra and indirectly pinpoint what kind of music they would make.

Damn Planets and their Rock Music…

Starting from our local solar neighborhood, it became apparent a decade ago that the closest planets emitted their own inaudible hum. For the Earth, if we throw out the din of human civilization, the dizzying menagerie of life around us, and subsurface tremors of earthquakes, we’re left with a residual white noise coming from the planet itself. In 1997, Naoki Kobayashi at the Tokyo Institute of Technology proposed that the lower atmosphere tugging and pushing the ground beneath it generates multiple echos within the planet of frequencies 0.01 Hz or less. Though this is far below the threshold for human ears, it’s technically loud enough that, if it were several octaves higher, would drown out everything else around us.

The other rocky planets in our solar system drone their own tune, each at different strengths that are set by their different atmospheric pressures. Mars, Earth, and Venus have fairly comparable internal densities, so their waves begin with similar amplitudes. But the thin atmosphere of Mars severely attenuates the sound strength by the time it reaches space, while Venus’ thick, choking blanket of carbon dioxide keeps the music alive with greater ease.

How much of a role do planetary atmospheres play in shaping these sounds? Several years ago, researchers at Penn State were morbidly intrigued by the Alien tagline, and decided to investigate how far a scream could theoretically be heard on Mars. They found that, while an average shriek could be heard for ¾ mile on our world, it would only go 53 feet in the atmosphere of Mars, which is 1% the density of ours. Its carbon dioxide air would noticeably lower the pitches produced by human vocal chords and geology alike.

More recently, scientists were able to hear actual sounds from Mars. Last May, the European Mars Express Satellite relayed the NASA Phoenix lander’s audio recordings it made during its descent to the planet’s surface. The probe is now settled comfortably in the artic wastelands of the Martian North Pole, hunting for frozen subsurface water. In orbit around Saturn, the Cassini spacecraft performed a similar task for Huygens in 2005, which recorded its own descent onto the moon Titan.

Our next and most prominent noisy neighbor is the sun, always a tumultuous hotbed of magnetically intricate flares, sunspots, and prominences. In October 2003, David Gurnett at the University of Iowa decided to take a particularly violent season of solar activity and scale the frequencies to the threshold of human hearing. Compressing hours of observations into a 15 second solar sound byte, the sun sounds more like a low-flying jet and hissing cockroach than a star.

But these are genuine sound waves. Electrons ejected in solar flares or the more massive coronal mass ejections move at a third of the speed of light, catching up with the surrounding solar “wind” of slower particles. Collisions between the two produce oscillations in the solar wind, observationally manifested as radio waves. These waves then decrease in frequency as the density of their medium decreases further away from the sun.

Milky Way Woodstock

Moving out to interstellar distances, astronomers also deduce sound waves in the gaseous nebulae that pepper our Milky Way Galaxy. The oft-imaged Orion, Horsehead, and Lagoonnebulae are particularly photogenic examples of these nurseries of star formation, dense agglomerations of interstellar gas, dust, and often shockingly complex organic molecules. Overall, these enormous, 10¹⁶ km- sized clouds maintain their shape through a delicate balancing act between the force of gravity, which wants to push everything together, and thermal pressure, which threatens to blow it all apart.

The particles in the nebulae, while at a chilly 10 degrees or so above absolute zero, move randomly and at varying speeds, creating momentarily denser regions where more particles have clustered together, and less dense regions where they have been evacuated. If these differences in particle density, or perturbations, are sufficiently small, they translate to transient disturbances in the nebula’s ambient pressure. This is the definition of sound. In this case it’s another messy static, with frequencies even lower than in moaning planets.

But if these perturbations are lucky, they may be large enough for gravity to win the war against thermal pressure, and trigger a local gravitational collapse that accelerates until a new star is born. These are the “failed” sound waves of which Astronomers are so fond. Then the freshly minted starstuff has the option of reverberating in all those exotic solar modes, not just listlessly wailing in the interstellar medium.

Other stars with masses 10 to 25 times that of the sun have a few more musical options. According to Adam Burrows at the University of Arizona, sounds waves generated in the death throes of the massive stars may provide the energy for supernovae, stellar explosions that are known to outshine entire galaxies at a time.

When a dying star has exhausted its nuclear fuel and fused its contents into iron, its interior is bereft of thermal pressure to support it against gravity, which demands its immediate collapse. New simulations predict that, within a second or two after this begins, the inner core of the star vibrates up to 200-400 Hz. Any observers not crushed by the gravitational stresses of a deflating star would be treated to a ubiquitous, ringing middle C. That is, until the sound waves propagate up to the outer layers of the star, heating them enough to blow them apart in a fiery supernova detonation.

But even then the symphony continues. The more massive stellar explosions may leave behind compact, spacetime-bending black holes, which will incite overtures in any interstellar “food” they’re offered.

The Universe is a Minor Key

The orbiting X-ray satellite Chandra in 2003 observed concentric shells of higher-pressure gas in the Perseus galaxy cluster, 250 million light years away from a suspected black hole. As intergalactic gas and dust spirals to its doom into the black hole, it is accelerated and compressed, causing it to radiate its energy outward in both energetic X-rays and physical compression waves, i.e. sound. Andrew Fabian and Steve Allen of the Institute of Astronomy in Cambridge found the shells produced by the latter phenomenon correspond to a B flat, but one so deep that it is 57 octaves below what we can hear.

This is no feeble tone, however. This black hole has been singing for an estimated 2.5 billion years, unleashing a total energy of 100 million exploding suns in the process. Astronomers theorize that this may be the heating mechanism responsible for keeping the tenuous gas they observe between galaxies so anomalously hot. Along with playful gravitational interactions between galaxies, this blistering gas provides the impetus for blue, star forming galaxies like our own to turn into quiescent red elliptical galaxies over time. As galaxies run across this intergalactic medium, their own star forming fuel is stripped away, leaving them to fade and redden as fewer new blue stars are born within them.

Astronomers can also synthesize music from the murmurings of the largest scales of the universe around us, stemming from the tiniest quantum-sized fluctuations billions of years in the past.

In practice, Astronomers can only see back to 380,000 years after the Big Bang, some 13.7 billion years ago. At this time of “recombination,” the expanding universe cooled enough for atoms to form from protons and neutrons. The light from this event has since expanded with the universe and cooled to a lukewarm 3 degrees above absolute zero. But by making some assumptions about the geometry and content of the Universe before this time, when the cosmos was too opaque to see anything, Mark Whittle at the University of Virginia made a sound clip chronicling our spacetime fabric’s first million years.

Compressing this time into a 5 second recording, the big bang sounds nothing at all like the awesome explosion many expect. Its stunning silence is a testament to its initial radial expansion, when no pressure waves yet congealed in the matter-energy soup. As quantum fluctuations begin to froth in this plasma of primordial matter, the cosmos adopt a major chord, switching to a minor third as time goes on.

Mathematically, this much like what occurs in the interstellar medium. The main difference here is that bigger and bigger disturbances are allowed as the scale of the universe increases. These pressure waves oscillate until atoms form, at which point the prevailing sound speed of the material in the Universe plummets. These waves effectively “stall out” and freeze at a distance scale of 150 million parsecs, or 4.6 x 10²¹ km.

Scientists can correlate these veritable wavesicles to the 3 degree Cosmic Microwave background, or CMB measured by projects like WMAP or BOOMERANG. The bubbly patches in CMB maps arise from temperature (or density) fluctuations at recombination, whose characteristic sizes tell us about the universe’s geometry and composition. Along with deep imaging surveys like Sloan and the 2 Degree Sky Survey, these “anisotropies” have hinted that the Universe is geometrically flat like some kind of three dimensional pancake, it has an unseen Dark Matter component that outweighs visible matter by ten to one, and an enigmatic, repulsive Dark Energy that outweighs both kinds of matter combined.

Notes from the Astronomy Underground: Just a Theory

Grading homework is a big part of the endless cascade of joy that defines grad student life. Personally, I get to evaluate almost 700 essays from an introductory astronomy course. It sounds pretty rough, but I really don’t mind it. It fits into my adorably naive crusade to make science more approachable for everyone and vaguely Make a Difference Somewhere.

Anyway, my mission for these essays is to look for what these students got out of the course; what part of Astronomy touched them personally. Pretty easy, right? Ordinarily, you’d expect Astronomy Newbies to be flabbergasted by the vast scales of the universe and our insignificance next to the astounding menagerie of stars, galaxies, quasars, dark energy, etc. Ideally, if these students are going to walk away from this course with anything, it’s an enlightened, albeit slightly depressing, cosmic perspective on humanity.

Well, for the most part it worked. A satisfying 60-70% of the class got the message and were somewhat inspired by the mesmerizing complexity of the universe. But the remaining students callously dismissed most of the course material, claiming everything they learned was “just a theory."

Just a theory.

Seriously, if I had a dollar for every time I read that exact phrase, I could put all the money in a big water tower and swim around in it like Scrooge McDuck did in Ducktales.

Everyone knows this isn’t a local phenomenon, either. If you’ve been following the Intelligent Design debacle in the U.S., you have a good idea of what I’m talking about. It’s been exhaustively covered by just about anyone with a working pulse, so I don’t need to discuss it here. But why would people want to be so willfully ignorant of science in the first place?

Fundamentally, it’s because people just don’t know what we do. I’m actually very sympathetic to that. As a grad student, I frankly never have a clue of what I’m doing, either. But I get the feeling that the public’s perception of modern science doesn’t resemble a tightly-knit, venerated community of the finest, meticulous minds on the planet so much as it does some horribly maladroit sequel to the Bill and Ted’s Excellent Adventure franchise.

Yeah… you may notice I’m quite fond of making marginally appropriate references to pop culture icons of the 1980s. You can expect a lot more of that in the future.

So how could the Me Decade’s favorite duo of SoCal burnouts personify these apparently easily rejected trivialities of science? I imagine it would go something like this:

Ted: Bill, my friend?

Bill: Yes, Ted, my friend?

Ted (gesturing wildly): Have you ever wondered how this… most excellent Universe came to be?

Bill: Dude… that is a most profound question. One that requires… philosophical musings of the greatest significance.

(Bill and Ted furrow their brows in thought)

Ted: Bill, what if… the Universe… started in a big bang. A most triumphant bang.

Bill: A most bodacious theory, my esteemed colleague. But what about the most uniform cosmic microwave background? It violates our most sacred laws of causality, dude.

Ted (dejected): Bogus…

Bill: Wait, Ted…. are you thinking what I’m thinking?

(Both perk up)

Bill and Ted in unison: INFLATION! DUDE!

(Both theatrically strum air guitars)

Now I’m not saying that Wyld Stylllyn cosmology is entirely without merit, nor am I trying to downplay how awesome a Van Halen-inspired spacetime metric could be. The point is, science doesn’t happen in three seconds. Astronomers don’t think up cosmic microwave background anisotropy because we’re annoyed at microwaves for unevenly heating our hastily purchased 7-11 burritos.

At the most basic level, the problem is a matter of transparency and semantics.

Aside from your celebrity scientists like Stephen Hawking, Lawrence Krauss, and Carl Sagan, scientists really are locked away in the proverbial Ivory Tower. It’s true in the most literal sense for me- I am literally locked in a windowless office tower, denied any contact with normal civilization. It’s bad. I think I'm starting to devolve into some kind of nocturnal mole creature. Granted, we scientists tend not to be the most socially graceful people on the planet, but that’s no excuse for our minimal integration into society.

“But wait!” You say. “Astronomy has a long, seasoned history of outreach. Surely that can’t be the main problem. Also, you are an amazing human being in every conceivable way. Your witty insight breathes new life into the very core of my being.” Well, you’re right. And thanks for your kind words. But really, it’s not the quantity of public relations that matters; it’s all about how we present the material.

For some bizarre reason, even when we teach the scientific method in middle and high school ad nauseam, most people seem to forget about the vitally important distinctions between hypotheses, theories, and laws by the time they go to college or to this “real world” I’ve heard so much about. It’s well known that our theories- our rigorously supported, peer-reviewed, and observationally/ theoretically consistent explanations of the universe- carry the same weight in the public domain as gut feelings and fairly arbitrary suggestions. That’s why the Theory of Evolution can occupy the same intellectual plane as 2005’s torrent of implausible predictions concerning the supposed invincibility of Chuck Norris’s beard.

What’s even worse is that we coldly summarize decades, even centuries, of scientists’ singularly driven passions into terse passages in both introductory textbooks and public literature. Every sentence you read in these books encapsulates someone’s individual contribution to science, cemented with decades of sacrifice, blood, and tears. And if he or she lived in the 1950s, it probably included plenty of cigarettes and red scare propaganda, too.

It’s an unfortunate, but necessary evil. With so much material to cover in classes or books, naturally we can’t delve into every minute detail about any particular theory. But then we invariably risk understating the years of mathematical and observational agony that is so essential to science, and giving the public this warped, Bill-and-Ted perspective on our research. We’re turning science into a running joke. Some of my students laugh at the Big Bang, claiming they could come up with equally plausible explanations to fit the limited number of observations we have time to make into crude sound bytes for them. We’re rapidly turning science education into a queasy circus of superficially crazy, poorly explained ideas, and I don’t see any appealing solution here.

But at the very least, we should at least tone down some of the religious language we use in our public discourse. I understand this is a deeply religious country, and drawing colorful analogies between faith and science may seem useful, but in reality this approach is as viable as using sheep as dinner napkins (I mean, eventually you’d run out of sheep). Every time Lee Smolin claims an aspect of cosmology is “an item of faith,” or Marcelo Gleiser writes about “Einstein’s complete faith in his ideas,” I spout threats of generic, self-inflicted eye injury. Almost every Astronomy educator is equally guilty of sprucing up science with inappropriate language. We “believe” in the Big Bang and Evolution, we are “agnostic” to ideas outside of our scientific “dogma,” and we “confess” that theory is not strictly the same as fact.

Ok, the last few examples are a little extreme. But “believe” and “faith” are in print in way more places than they should rightfully be. These semantic tangles pit science against religion in a wholly unneeded, bitterly divided theological battleground, and this is the worst kind of publicity we could possibly get. Science and Religion are not Rock ‘Em Sock ‘Em Robots awkwardly fighting in some ideological arena; nor are they contenders for class time in science curricula (I’m talking to you, Kansas). Somehow we’re putting what should be two complementary aspects of our humanity through a kind of twisted intellectual schizophrenia. And all this because we’re getting sloppy with our language and inadvertently transforming the country’s view of science.

Yikes. I didn't really intend to go that far into religion. For the record, I consider science and religion to be perfectly compatible. To be quick, I'll refer you to the philosophical works of Eddington, Jeans, Schrödinger, and Whitehead. For a bunch of dead white guys, they're alright.

What’s the next step? We could probably use some serious pedagogical backpedaling. By trying to make science universally accessible, we’ve harnessed the connotative power of the English language and obscured our beloved fields so much that no one understands the difference between a genuine theory and an idea any more.

So until we can get everything straightened out, in the words of my favorite, oft-quoted characters, just be excellent to each other.

Gleiser, M. 2005, The Dancing Universe, Hanover, NH: Dartmouth University Press.

Smolin, L. 2006. The Cosmic Landscape, New York: Little, Brown, and Co.

http://i.cnn.net/cnn/2003/SHOWBIZ/Movies/11/05/sprj.caf03.film.keanureeves.ap/story.bill.ted.ap.jpg

Notes from the Astronomy Underground: Another Shameless Plug

A.k.a. The Digital Universe: Now with 10% more dark energy.

Things have been rather frenzied this summer, to say the least. I'm quickly learning that the once-venerated HST is a dilapidated geriatrics ward of telescopy, one whose shoddy WFPC2 camera I can only imagine was MacGuyvered from popsicle sticks, dryer lint, and unsold copies of Deep Blue Something's latest album. Because, well, we're never really going to run out of those, now are we?

But there has been one very positive development in the last few months. As a serious Dude of Outreach here, I've had a chance to look into the Hayden Planetarium's latest version of their Digital Universe Atlas. This runs on Partiview, visualization software that allows you the thrill of aimless, haphazard flight without the disappointment of waking up from that amazing dream or crashing from that Friday night post-rave mescaline high.

Or in my case, it saves me from doing grownup work and lets me play with astronomical pornography all day.

And let me tell you, this stuff is pretty awesome. NotThe Dark Knight awesome, sure, but at least this won't leave you sobbing silently into your pillow from a deluge of unmitigated angst and cinematic despair afterward. I pieced together a tour of the Universe for this month's Astrofest, and seeing those galaxies spinning around in a polarized eyeglasses-induced 3D perspective is almost as cool as punching out that vapid animatronic gopher that sells lottery tickets on TV here would be. Seriously, Pennsylvania, I'm sure you can tax poor people in a less sadistic way.

The salient point, however, is that the software is completely FREE. Which, to a grad student, is the most beautiful word in the English language. Unless of course, it's a preface to “free colonoscopy,” or something.

Anyway, here's a quick, abbreviated selection of screen shots, similar to what I would show in a typical presentation:

Our lovely home in the cosmos- the Milky Way, surrounded by Large and Small Magellanic clouds, a smattering of boring dwarf galaxies, and a superimposed spherical grid indicating the maximum extent of Patrick Swayze's creepiness.

The Andromeda galaxy and its dwarf companions, looking back on the Milky Way. Looks kind of lonely and bitterly ostracized out here, doesn't it? It's giving us the shifty eye out there, hovering in the distance, endlessly plotting its unspeakable revenge. Kinda like Gargamel from the Smurfs, when you think about it.

The view from the interior of the Virgo cluster, a metropolis of 2,000 + galaxies, Alicia Silverstone's career, and where your puppy actually went when your parents told you he went to go live on a farm Upstate.

The clumpy distribution of galaxies in our universe on larger scales. Any aliens out here will still be blissfully unaware of the XFL and The Magic Hour with Magic Johnson for another ten million years. But the clock for them is ticking.

Galaxies in the 2MASS catalog demonstrating their preferential distribution into city-like clusters (red dots), highway-like filaments (green-yellow dots), and nearly empty voids. The so-called “Great Attractor” is up at the top right, a spot in the universe drawing in the nearest 100 million galaxies at speeds from 600-1000 km/s. This is a place of enormous gravitational significance, matched only by Michael Flatley's 1996 post-Riverdance ego.

Here we've zoomed out to scales of tens of billions of light years, or a volume of the universe encompassing just about everyone who would rather drive a flaming pitchfork into his spinal cord than see Space Chimps. Note the honeycomb pattern of clusters, filaments and voids, along with our incomplete coverage of the sky.

One of the trippier overlays: the WMAP cosmic microwave background map placed in the distance at the epoch of recombination. In the foreground are Sloan-imaged quasars, then more normal galaxies and well-defined large scale structure as you move towards the present at the bottom right. This splotchy color scheme is also what I saw when I slammed my head into a door a week ago.

What I personally find even more exciting is the enormous potential this software has for high school- introductory level astronomy education. This package has some rudimentary statistics commands and visualization procedures for picking out subcategories (e.g. galaxy morphology, luminosity, redshift...) and doing actual analysis while you're looking right at your universe. You can spin clusters around while looking at the morphology-density relationship for galaxies, zoom out and do a census based on any neophyte-applicable observable, or comb through the Great Wall of galaxies. And that's just for the “Extragalactic” shell. The “Milky Way” variant has a striking tableau of accurately rendered nebulae, molecular clouds HI, OII, and HII regions, and the galaxy viewed from the inside in radio to gamma wavelengths. Plus, you can visualize where all our extrasolar planets have been lurking in space.

I've been waiting for something like this for a long time. Well, that and for microwaves to stop having that damn “timed cook” button on them. I mean come on, you're a microwave, it's cooking something for a specified length of time is what you do. I shouldn't have to press an extra button for this.

So definitely check this stuff out! The 300+ page manuals can seem a little daunting, but a lot of the commands they go over are mighty useful. And stay tuned for what's hopefully the final installment of the Unappreciated Topics in Astronomy series, provided I can find my kneecap-busting crowbar and track down my remaining interviewees. You either talk about astronomy, or get Nancy Kerriganed. That's just how I roll.

Notes from the Astronomy Underground: A Shameless Plug

Pardon the interruption from the customary, marginally sensible hodgepodge of topical humor and astronomy exposes, but there's a lot of interesting stuff afoot in central Pennsylvania in July.

If you're around the Keystone State (the arch support structure, not the beer) in the upcoming month, you should definitely check out the PSU Astronomy Department's table at the BJC when you come for the most excellent Independence Day fireworks show. Why is that, you ask? Well, we're handing out these pretty crazy-looking prism masks through which the fundamental mysteries of fireworks will be revealed.

No, sadly, you can't see through that hot girl's clothes with these.

It really compliments all the other American July 4th traditions. Barbecue-induced, hedonistic food hangovers, parades, fireworks... and now spectroscopy. Perfect fit, if you ask me. Here's the original press release for the event:

Every year on this day, brilliant explosions of red, white, and the deepest blue light up balmy evening skies. There's nothing quite like a riveting fireworks show to cap off an Independence Day full of barbecues, parades, and family reunions. But have you ever wondered just what gives our annual pyrotechnic displays their stunning array of colors?

This year at the Central PA 4thfest, visitors are invited to see the inner atomic workings of this priceless facet of Americana from the safety and comfort of their lawn chairs and picnic blankets. Courtesy of the Penn State Department of Astronomy and Astrophysics, special masks will be provided free of charge that allow eager spectators to identify the very atoms and molecules that produce the brilliant colors of fireworks.

“Every bit of light our eyes see, every photon, is like a footprint of the process and element that made it,” explains Brendan Mullan, a grad student in astronomy. “Within atoms and molecules, whenever an orbiting electron jumps around, it emits a photon of a specific color. When we see that color, we know it must come from a particular electron jump of a particular element.”

The secret behind these masks lies in their prism-like ability to break light up into its individual colors across the rainbow, or spectrum. With these, spectators can identify the characteristic spectra of atoms and molecules just by enjoying the fireworks show. “This is a two-fold opportunity for people,” says Chris Palma, outreach coordinator for the university. “Not only does everyone get a chance to see how astronomers identify elements in stars but looking at their light, but they also get to apply this technique to something fun like fireworks.”

It's a unique demonstration of how astronomers can determine the composition of extremely distant objects without ever visiting them, one of the most powerful observational tools at their disposal. It's also a preview of some of the exciting activities in store for the upcoming, popular “Astrofest” event later in the month.

The eyeglasses will be distributed from 4:00pm – 8:00 pm July 4th, at the Astronomy Department's Founders' Mall table at the Bryce Jordan Center.

And perhaps most importantly, we have Astrofest, the 4-day bender of astronomy outreach July 9th through the 12th, that I am confident will totally blow you away. Here's the story on this veritable Astropalooza:

A free festival of astronomy will be held from 8:30 pm to 11:30 pm on Wednesday, July 9th through Saturday, July 14th, on the Penn State University Park campus. The 10th annual “Astrofest” is sponsored by the Penn State Department of Astronomy and Astrophysics.

Originally conceived as a way for the department to share astronomy and its discoveries with the public, the 4-day event has since exploded into an elaborate production with more than 60 faculty, students, and staff helping to entertain about 2000 visitors each year.

This year, Astrofest offers a brand new series of 3D tours of Mars, the Milky Way, and the universe beyond our galaxy. In addition, presentations will be offered each night on a wide range of cutting-edge topics, from the search for life in the universe, to hands-on demonstrations of “night vision astronomy,” to great astronomical disasters. “We're trying out a lot of exciting new content this year,” says Brendan Mullan, a grad student in the department. “The popular 3D tours have been almost completely redesigned, and the presentations feature a lot of new technology and content we haven't used before.”

Astrofest invites people of all ages to celebrate astronomy. For children, there are crafts, solar system tours, a Drivers Ed class of sorts for a Mars rover, planetarium shows, an opportunity to build a comet, and more. Kids are also encouraged to try and complete a “passport” to win small astronomy-themed prizes.

If the sky is clear, visitors are invited to observe a number of astronomical objects through the telescopes on the Davey Lab rooftop observatory. The planet Jupiter and its moons will be in an ideal position in the sky, as will our own Moon and its prominent craters. To top it off, fuzzy nebulae, and clusters of millions of stars will also be featured on the stargazing menu.

“Davey Lab is very close to the Arts Festival, which is very convenient for people to drop by in the evening and see what's going on at Astrofest,” adds Jane Charlton, professor of Astronomy and Astrophysics, and the organizer of Astrofest. “Even though there'll be plenty to do indoors if the weather doesn't cooperate, we're still hoping for clear skies and a record-setting attendance for this year's events.”

I know, I know... I interviewed myself in these things. It wasn't intentional- it's just that nobody tends to be awake at the hours that I do this kind of work. Well, not awake in this continent, anyway.

But in all seriousness, I strongly urge you to come on over and see what we've got. Personally, after completely retooling the 3D tour of the clusters, filaments, and voids that form the large-scale structure of the cosmos, and updating the visualization software, I'm pretty psyched to show the public some intense Jerry Bruckheimer-style galaxy eye candy.

I mean, good Jerry Bruckheimer, not like Armageddon Jerry Bruckheimer.

The Night Sky: October 2008

The Night Sky in October 2008

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
Full "Hunter's" Moon on the 14thNew Moon on the 28th

Stars and Constellations
The month of October bids farewell to the stars of summer and ushers in the autumn sky. You will also notice that the sky gets dark considerably earlier than it did in September. Arcturus, the fourth-brightest star in the sky, can be spotted as it sets low in the west-northwest, its orange color a fitting tribute to the pumpkin harvest at this time of year. Antares in Scorpius may still be glimpsed very low in the southwest after sunset, but most of the rest of Scorpius is lost in the glare of twilight. Following Scorpius in the southwest is Sagittarius, the Archer, followed in turn by the faint constellation Capricornus, the Sea Goat. The “summer” right triangle is just west of overhead by 8 pm EDT in mid-October. Despite the designation, this trio of bright stars Vega (in Lyra), Deneb (in Cygnus), and Altair (in Aquila) will remain visible in the early evening sky through early winter.

As evening unfolds, the stars of autumn begin to take center stage. Low in the southeast after 9 pm in mid-October is the whitish star Fomalhaut, located in Pisces Austrinus, the Southern Fish. Lying just above Pisces Austrinus is Aquarius, the Water Bearer. The Great Square of Pegasus, which is actually a rectangle consisting of four stars, is situated high in the south-southeast at about this same time, and is another sure sign of autumn. High in the northeast is the famous “W” shape of the constellation Cassiopeia, the Queen of ancient Ethiopia. The “W” opens up toward Polaris, the North Star. Polaris actually consists of three stars, the brightest of which is a supergiant star with a luminosity of 2500 suns. It is also classed as a pulsating variable star known as a Cepheid (after the prototype in the constellation Cepheus). Such stars expand and contract in size in cycles of several days. In the case of Polaris, its pulsation cycle takes 4 days. Polaris lies at a distance of 431 light years from our solar system.

Between Pegasus and Cassiopeia lies the constellation Andromeda, the chained maiden in Greek mythology. This faint constellation contains within its boundaries the famous Andromeda Galaxy, which lies over two million light years from our solar system. The Andromeda Galaxy is often thought of as a sister galaxy to our own Milky Way, and is the most distant object visible (though barely) to the naked eye. The now obsolete Y-shaped group Gloria Frederici (Frederick’s Glory) lies in the region between Andromeda, Cassiopeia, and Lacerta. It was created by Johannes Bode around 1790 in memory of Frederick the Great of Prussia, who had died a few years earlier. Its stars have since been absorbed into Andromeda and Cassiopeia.

Planets
Venus continues its slow ascent into the evening sky, resembling a very bright star low in the west. It sets only about an hour after the Sun at the beginning of October, but 2 hours after it on Halloween. Venus moves from Libra to Scorpius during October, and passes close to Antares during the last week of the month. In another month or so, Venus will be a truly magnificent beacon in the western sky at dusk. Jupiter continues to dominate the night sky during October, resembling a brilliant cream-colored star as it slowly glides above the southern horizon during the evening hours. Jupiter currently resides within the constellation Sagittarius, positioned just above the famous “teapot” asterism. At the beginning of October Jupiter lies due south at dusk, and sets around midnight. By the 31st, Jupiter sets around 10 pm. At the end of November, Venus will pass close to Jupiter, and the pairing of these two bright planets will make for a truly dazzling sight in the evening sky.

Saturn is now easily spotted in the east before dawn, resembling a bright yellow star in the constellation Leo. It rises around 5 pm EDT on the 1st, but by 3:30 am at month’s end. Mercury reaches inferior conjunction with the Sun on the 6th, and so is not visible at all during the first week of October. Soon afterwards, however, Mercury rapidly emerges into the morning sky, and just a week after conjunction it rises an hour before the Sun, looking like a moderately bright star low in the east just before dawn. On the 22nd, Mercury reaches its greatest elongation from the Sun, rising nearly two hours before sunrise, and it continues to be in good position for viewing right through the end of the month. Mars, now closely aligned with the Sun, will be lost from view for several months. Mars reaches conjunction with the Sun in early December (nearly a year after its fine opposition and close approach to Earth in December 2007), and will slowly re-appear in the morning sky in early 2009.

The Orionid Meteor Shower peaks after midnight on October 20. Expect about 10-12 meteors per hour, appearing to emanate from the constellation Orion, which will be rising in the east just before midnight.

Some content for this article has been obtained from US Naval Observatory Data Services

The Night Sky: September 2008

The Night Sky in September, 2008

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in September
Full "Harvest" Moon on the 15thNew Moon on the 29th

Stars and Constellations
Despite the formal arrival of autumn in September, the stars of summer (and even a few of spring) are still well placed for viewing during the early evening hours. By about 9 pm, orange-colored Artcurus in the constellation Boötes, the Herdsman, is low, but still visible, in the west. Somewhat above Boötes is Corona Borealis, the Northern Crown. The Big Dipper, a part of the constellation Ursa Major, is low on the northwestern horizon, and so you will not be able to see it if trees or buildings obstruct your view of this part of the sky. The handle of the Dipper "arcs" to Arcturus. Orange-red Antares in the Scorpion is quite low in the southwest. You should also be able to find the asterism known as the "teapot" of Sagittarius, just east of Antares. The constellation Sagittarius contains the nucleus or core of our own Milky Way Galaxy, which may be seen (if you are away from urban lights) as a hazy band stretching across the sky. The summer triangle of Vega in Lyra, Deneb in Cygnus, and Altair in Aquila is nearly overhead for a couple of hours after sunset.

Three relatively faint, diminutive constellations can also be found on late summer evenings if the sky is dark and clear enough: Delphinus (Dolphin), Sagitta (Arrow) , and Corona Australis (Southern Crown). The Dolphin and Arrow lie above and to the left of the Eagle, while the Southern Crown lies just below Sagittarius. According to Greek mythology, the poet and musician Arion had won prizes in a musical contest in Sicily. While sailing home to Corinth, the ship's murderous crew seized his prizes and threw him overboard. A kindly dolphin rescued Arion, however, and carried him ashore. Years later, when the dolphin died, it was placed among the stars as the constellation Delphinus, in recognition of this noble deed. Sagitta was the arrow of Apollo which he used to kill the Cyclops, the producer of Zeus's thunderbolts. Later Apollo changed the arrow into a constellation to commemorate his battle with the Cyclops. Corona Australis, the southern counterpart to Corona Borealis, is said to represent a laurel wreath worn by Sagittarius, the Archer.

As the stars of summer gradually fade into the evening twilight, the first stars of autumn are rising in the eastern sky. Making its appearance in the southeast after about 10 pm EDT is the white star Fomalhaut, which lies in the constellation of Pisces Austrinus (the Southern Fish). Rising due east at about this time is the Great Square of Pegasus, four whitish stars in the form of a rectangle (not quite square) lying on its edge. Low in the northeast is the famous "W" shape of the constellation Cassiopeia, the Queen of ancient Ethiopia. The "W" opens up toward Polaris, the North Star. A faint, but important constellation lying just above Cassiopeia is Cepheus, the King of Ethiopia and Cassiopeia's husband. One of Cepheus's seemingly insignificant member stars is mu Cephei, also known as "Herschel’s Garnet Star." This name refers to the star’s intensely red color, a result of its relatively cool temperature. Mu is listed in University of Illinois astronomer James Kaler's book, The Hundred Greatest Stars (New York: Copernicus Books, 2002) as one of the largest and most luminous stars in the Galaxy. It lies at a distance of about 2000 light years from our solar system.

Planets
Mercury can be glimpsed very low in the evening twilight sky for the first half of the month. It looks like a moderately bright star. Mercury keeps close company (apparently) with two other terrestrial planets, Venus and Mars, for much of the month. By month’s end, Mercury disappears into the evening twilight. Venus continues its slow ascent into the evening sky, resembling a very bright star low in the west. It sets only about an hour after the Sun for much of September. It will be another month or two before Venus rises to true magnificence in the evening sky. For now, the interest lies in the clustering of Venus with fellow terrestrial planets Mercury and Mars, low in the western sky shortly after sunset. Mars is by far the faintest of the three, and will be essentially vanishing from the evening sky by the end of this month.

Jupiter remains well positioned for viewing during September. It resembles a brilliant cream-colored star hovering well above the southern horizon during the evening hours. Jupiter continues to reside within the constellation Sagittarius, near the famous "teapot" asterism. In mid-September, Jupiter reaches its highest point above the southern horizon (i.e., transits the meridian) around 8 pm and sets at about 1 pm, EDT. Saturn reaches conjunction with the Sun on the 4th, and hence is inaccessible for viewing early in the month. By midmonth, however, Saturn rises an hour before the Sun and by the 30th about 2 hours before it. Look for Saturn in the east at dawn – it resembles a bright yellow star in Leo.

Earth reaches the September Equinox in its orbit on September 22 at 11:44 am EDT, marking the beginning of autumn in the Northern Hemisphere. This date was previously referred to as the Autumnal Equinox, but a neutral designation is now used to acknowledge the fact that spring also begins on this date in the Southern Hemisphere.

Some content for this article has been obtained from US Naval Observatory Data Services

The Night Sky: August 2008

The Night Sky in August, 2008

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in August
New Moon on the 1stFull "Sturgeon" Moon on the 16th

Stars and Constellations
As darkness falls on clear August evenings, the first star to appear is orange-yellow Arcturus, which stands high in the west about an hour or so after sunset. This identification can be verified once it gets dark enough to locate the Big Dipper, a part of the constellation Ursa Major, which is beginning to dip into the northwest. The two bright stars in the front of the Dipper, Merak and Dubhe, point to Polaris, the North Star, while the “arc” of the Big Dipper’s handle leads to Arcturus. If the sky is dark enough, you may be able to see the Little Dipper, which is part of Ursa Minor, extending outward from Polaris toward the upper left. Try also to make out the large, but faint summer constellation Draco, which winds across the sky high above the Little Dipper. Draco represents the mythological dragon that guarded the golden apples in the Garden of the Hesperides. As one of his twelve labors, Hercules slew the dragon and made off with the apples. Draco is especially notable because one of its stars, Thuban, was the polestar some 4000 years ago.

You may be able get one last glimpse of the spring star Spica as it sets in the southwest. To the far left of Spica is orange-red Antares in Scorpius, the Scorpion, which is visible low in the south-southwest. The body of the Scorpion snakes down toward the horizon and then upward into a curved stinger. Look closely, and you will see the “cat’s eyes,” a pair of stars located at the end of the tail which seem to be winking at you. Shaula is the left and brighter of the two stars, while Lesath is the fainter one on the right. To the upper left of the cat’s eyes is the “teapot” of Sagittarius, an easy grouping to identify. The teapot marks the general direction of the center of our Milky Way galaxy. If you live away from city lights, you can make out the Milky Way as a hazy band stretching across the sky from southwest to northeast. In fact it passes through the region of the summer triangle, which at this time stands high in the east-northeast. The triangle is comprised of Vega in the constellation Lyra (the Harp), Deneb in Cygnus (the Swan), and Altair in Aquila (the Eagle). About halfway between Vega and Altair is the moderately bright star Albireo, also known as beta Cygni. A telescope reveals that this star is actually two stars, one yellow and the other blue. The color of a star indicates its surface temperature: blue stars are the hottest (upwards of 20,000 °F), white stars are less so (15,000 °F), yellow stars like the Sun are moderately cool (11,000 °F), and red stars like Antares are the coolest (6000 °F or less). All three stars of the summer triangle are whitish in color, indicating that they are all somewhat hotter than our Sun.

On August evenings you should be able to distinguish the “W” shaped constellation Cassiopeia as it rises low in the northeast. Late in the evening the Great Square of Pegasus, which consists of four stars in the form of a rectangle lying on its edge, can be seen rising in the east. These are two signs that autumn is just around the corner!

Planets
Mercury is lost in the evening twilight in early August, but by mid-month it has risen high enough to be seen low in the northeast within an hour or so after sunset. Also in mid-August, Mercury passes close (apparently) to Saturn and a few days later Venus. Speaking of Venus, it is beginning to make a gradual reappearance in the evening sky, but you will need an unobstructed western horizon to see it low above the western horizon. During the month of August, Venus sets at best only about an hour after the Sun; not until late October will it become truly prominent. Saturn is still visible low in the west at the beginning of August, setting a little over an hour after the Sun. Venus and Mercury pass very close (as seen from Earth) to Saturn on the 13th and 15th, respectively, making for a marvelous sight in binoculars or a small telescope. By month’s end, however, Saturn will have disappeared into the evening twilight, only to reappear in September in the morning sky before sunrise.

Mars can be spotted in the western sky shortly after sunset, to the upper left of Saturn and Venus. Mars is now on the opposite side of the Sun from the Earth, and hence is much fainter than it was back in December 2007 when it was closest to Earth. Mars sets about one and a half hours after the Sun in mid-August. Jupiter is in fine position for viewing this August. It resembles a brilliant cream-colored star as it hovers above the southeastern/southern horizon during the evening hours. Jupiter continues to reside within the constellation Sagittarius, just to the east of the famous “teapot” asterism. In mid-August, Jupiter reaches its highest point above the southern horizon (i.e., transits the meridian) around 10 pm and sets at about 3 pm.

Earth passes through the debris of Comet Swift-Tuttle on August 11-12, producing the Perseid Meteor Shower. Meteors should become visible in late evening, with the best show occurring after midnight. Look toward the northeast, but meteors can be seen in any part of the sky.

Some content for this article has been obtained from US Naval Observatory Data Services

Back to the Moon

Current plans call for NASA to land astronauts on the Moon in 2020. Given past history of ambitious programs like this, it is reasonable to expect this to slip by a few years, so let’s say it occurs in 2022. What is the significance of that? Well, that would make it exactly 50 years between the last moon landing, by Apollo 17 in 1972, and a return. Who would have thought, in the heyday of the Apollo missions, that it would take half a century to get back to where we’ve been before. At the time of the first moon landing in 1969, I would have bet that by 1990, or surely by 2000, we would have a lunar base and a mission to Mars. Following are NASA’s six stated reasons for going back to the moon. I welcome comments from readers on why things have gone as they have and where they should go from here.

Concept of a future moon landing.
Credit: NASA/John Frassanito and Associates

Six lunar exploration themes evolved from the recent Global Exploration Strategy discussions. NASA engaged the global space community to develop the themes by asking the question, “Why should we return to the Moon?”

From the answers emerged six common areas of interest – six areas of pursuit which, seen through the eyes of the world, define the value of going to the moon. NASA took these six ideas and worked with other space agencies to develop the following lunar exploration themes.

Human Civilization — Extend human presence to the Moon to enable eventual settlement.

Scientific Knowledge — Pursue scientific activities that address fundamental questions about the history of Earth, the solar system and the universe - and about our place in them.

Exploration Preparation —
Test technologies, systems, flight operations and exploration techniques to reduce the risks and increase the productivity of future missions to Mars and beyond.

Global Partnerships — Provide a challenging, shared and peaceful activity that unites nations in pursuit of common objectives.

Economic Expansion — Expand Earth’s economic sphere, and conduct lunar activities with benefits to life on the home planet.

Public Engagement — Use a vibrant space exploration program to engage the public, encourage students and help develop the high-tech workforce that will be required to address the challenges of tomorrow.

Detecting Extrasolar Planets

The first detection of extrasolar planets was announced in 1995 by two competing groups. One was headed by Geoff Marcy, then at San Francisco State University, the other by Michel Mayor at the Geneva Observatory. The same technique was used by both: measuring the back and forth motion of a star due to the “teeter-totter” like reaction induced by the orbiting of a massive planet. In the case of our own solar system, this motion would be predominantly due to Jupiter. Since the Sun outweighs Jupiter by more than a factor of 1000, the Sun’s back and forth motion is tiny: about the speed of a good runner. It is amazing that this can be precisely measured. To date well over 200 planets have been discovered using this technique, and in a few recent cases, as precision keeps improving, even multiple planets around a star can be extracted from the data.

Scale diagram of planet/star ratio for the WASP Planets. (Credit: SuperWASP project)

As powerful as this technique is, there are unavoidable limitations. We cannot measure the sizes and masses of planets accurately (because we do not know how tilted to our line-of-sight the orbits are). The technique is intrinsically biased toward the most massive planets in close orbits. That’s why so many of the planets are much more massive than Jupiter yet orbit their stars at distances closer than Mercury in our solar system.

A complementary technique is now showing its worth: planet transits. If we are lucky enough to be almost directly in the plane of the orbit of a planet, we can spot the transit of that planet against its sun. This happens here too. Venus transits the Sun as viewed from the Earth every now and then. On other stars we cannot image the planet as it crosses a stellar disk, but it is possible to measure changes in brightness with such precision that dips in the brightness of a star can be used to infer that a planet is crossing. This allows the actual size of the planet to be inferred from the dip in the star’s light (assuming we can infer the radius of the star from its spectral type).

Given that we need to rely on chance alignments of the orbital planes and transits that briefly happen every few months or years for those lucky alignments, you would not think that this looks too promising. It requires monitoring hundreds of thousands of stars all at once to stand a chance of catching one of those rare events.

Amazingly this can be done, and this technique has now resulted in 46 planet detections from ground-based observatories. The latest announcement comes from astronomers at the University of California, Santa Barbara, who have found ten new planets in a project called SuperWASP, for Wide Area Search for Planets. Planets found range from half the size of Jupiter to eight times as large.

This technique is being taken into space. The NASA Kepler Mission, scheduled for launch in February 2009, is designed to find planets 30 to 600 times less massive than Jupiter. As NASA states: To detect an Earth-size planet, the photometer must be able to sense a drop in brightness of only 1/100 of a percent. This is akin to sensing the drop in brightness of a car’s headlight when a fruitfly moves in front of it!

The Kepler Mission, a NASA Discovery mission, is specifically designed to find Earth-like planets in the habitable zone, which encompasses the distances from a star where liquid water can exist on a planet’s surface. It is amazing how quickly we are obtaining actual observations zeroing in on that most profound of questions: Are there other civilizations out there in the Universe?

Press Release from University of California, Santa Barbara.

NASA Kepler Mission home page.

The Night Sky: July 2008

The Night Sky in July, 2008

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in July
New Moon on the 2ndFull Moon on the 18th

Stars and Constellations
As July opens, most of the spring stars are disappearing into the twilight, not to return to the evening sky until early in 2009. Blue-white Regulus, in the constellation Leo, is moving toward the western horizon in early evening and sets around 10 pm in mid-July. Blue-white Spica, in Virgo, sets in the southwest around midnight. Yellow-orange Arcturus is usually the first star to be spotted high as twilight fades into night. Arcturus, in the constellation Boötes, is located high in the south in early evening, and remains visible until it sets around 3 am at midmonth. Although it is considered a spring star, Arcturus will remain in good position for evening viewing through October. As the bright stars of spring are setting toward the western horizon, a trio of summer stars is rising in the east. This is the famous Summer Triangle, comprised of Vega in the constellation Lyra (the Harp), Deneb in Cygnus (the Swan), and Altair in Aquila (the Eagle). Moving into view in the south-southeast in early evening is Antares, a red supergiant star in the magnificent summer constellation Scorpius.

Located between Virgo and Scorpius is the faint constellation Libra, the Scales of Justice. An historical sidenote is that the stars of Libra were once designated part of Scorpius, and in fact composed the claws of the Scorpion. Libra’s northernmost star, Zubenelchemale, which means “northern claw,” is known for its greenish color. Like its neighbors Virgo and Scorpius, Libra is a zodiac constellation, which means that the Sun passes within its boundaries during the year. At present, the Sun passes through Virgo between September 16 and October 30, through Libra between October 31 and November 22, and through Scorpius between November 23 and November 29 (only about a week). After Scorpius, the Sun’s annual path takes it through the “unofficial” zodiac constellation Ophiuchus, the Serpent Holder (the symbol of the American Medical Association), between November 30 and December 17, and then through Sagittarius between December 18 and January 18. These dates gradually change over the centuries due to a long term wobble, or precession, of Earth’s axis. Precession explains why the actual dates of the Sun’s passage differ by about one full month from the astrological signs of the zodiac, which were devised over two thousand years ago.

Planets
Last month Venus was in conjunction with the Sun and hence lost in its glare. By late July, Venus will begin to reappear low in the evening sky after sunset, but you will need an unobstructed western horizon to see it. Venus sets only about 45 minutes after the Sun at month’s end. As July begins, Mars is located a little above Regulus in Leo, making for an eye-catching pairing of a planet and a star. The two objects are roughly the same brightness (Mars is just slightly fainter than Regulus), but the color contrast is fairly distinct, especially when seen through binoculars. Mars has yellow-orange color, while Regulus is bluish-white. Mars slides rapidly eastward during the month, and by the 9th, Mars will form another tight pairing, this time with the planet Saturn. Mars sets about 11 pm EST on the 1st of July, and by 10 pm on the 31st. Saturn resembles a bright yellow star in Leo, lying to the upper left of the bright star Regulus. Saturn will be joined by Mars on the 9th and 10th, at which time the two will be less than two Moon diameters apart. Saturn remains well placed for evening viewing for most of July; it sets about 11:30 pm on the 1st and by around 9:30 pm on the 31st.

Jupiter reaches opposition with the Sun on the 9th of July, when it will be closest to Earth and in optimum position for viewing all night long. Jupiter resembles a brilliant cream-colored star, and cannot be missed once it clears the southeastern horizon during the evening hours. Jupiter continues to reside within the constellation Sagittarius, just below the famous “teapot” asterism. Even a small telescope should reveal Jupiter’s brighter moons, as well as its cloud bands and famous Red Spot. In early July Mercury can be seen low in the northeast within an hour or so before sunrise. It will remain visible in the morning sky for much of July, but at the end of the month Mercury reaches inferior conjunction with the Sun and becomes lost in its glare.

For more information on astronomy and weather, visit the Widener University Public Viewing Website at http://www.widener.edu/stargazing/, then click on Web Links & Resources.

A set of free sky maps can be obtained at http://www.skymaps.com/

The Night Sky: June 2008

The Night Sky in June, 2008

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in June
New Moon on the 3rdFull Moon on the 18th

Stars and Constellations
Astronomical summer begins at 7:59 pm on June 20th, at which time the Northern Hemisphere of Earth is tilted at its greatest angle toward the Sun. Nevertheless, the stars of spring are still in excellent position for viewing during June. One of the most famous spring stars is bluish-white Regulus in the constellation Leo, the Lion. Regulus stands high in the southwest in early evening, and sets around midnight. A star with similar color and brightness is Spica, which stands about halfway up in the south shortly after nightfall. But the first true star to become visible in evening twilight is Arcturus, the fourth brightest star in the entire sky, in the constellation of Boötes, the Herdsman. Arcturus has a distinct yellow-orange color, and at around 9 pm EDT lies high above Spica in the south. To find Arcturus and Spica, first locate the Big Dipper, and follow the arc of the Dipper’s handle outward until you encounter Arcturus, then continue on to meet Spica. To the east of Spica in Virgo is the next zodiac constellation Libra (the Balances). Its two brightest stars are Zubenelgenubi, which is actually two stars in orbit about each other, and Zubeneschamali, which in a telescope appears to have a greenish color.

If the sky is especially dark where you live, try to locate the semicircle of stars representing the constellation Corona Borealis (Northern Crown) just a bit above and to the left (east) of Arcturus. In mythology, Corona Borealis represented the crown of Princess Ariadne, daughter of King Minos of Crete. The crown’s brightest star is blue-white Alphekka, also known as Gemma. To the left of Corona Borealis is Hercules, the fifth largest constellation in the sky. The brightest star in Hercules is alpha, also known by its proper name Rasalgethi. It is both a variable star and a double star.
One of the lesser known spring constellations is Canes Venatici (Hunting Dogs), which passes nearly overhead in the early evening hours of June. This tiny group was originally part of Ursa Major, but in 1690 Johannes Hevelius introduced it to represent a faithful pair of Hunting Dogs to accompany Boötes, the Herdsman. Canes Venatici contains only one relatively bright star, Alpha Canum Venaticorum, better known as Cor Caroli, or “Heart of Charles.” The name was possibly bestowed by Edmond Halley in the late 1600s in honor of his king, Charles II. When viewed through a telescope, Cor Caroli is revealed to be a magnificent double star, with the brighter component blue and the fainter one yellow. The blue star is especially peculiar, showing evidence of a powerful magnetic field. The system lies about 110 light years from our solar system.

Planets
As June begins, Mars is located in the faint constellation Cancer, roughly halfway between the more prominent zodiac constellations Gemini (where Mars spent several months earlier in the year) and Leo (its next stop). As the month progresses, Mars slides eastward into Leo, where it joins current planetary resident Saturn. By month’s end, Mars will sidle up close to Leo’s brightest star Regulus, making for a very pretty sight. Mars resembles a moderately bright, yellow-orange star, a little fainter than Regulus, and continues to be favorably placed for evening viewing during June, setting a little before midnight at midmonth. Saturn resembles a bright yellow star lying next to the fainter, blue-white true star Regulus. In late June, Mars will join them in Leo. Saturn is ideally located for evening viewing; it remains visible until after midnight for much of June.
Jupiter resembles a brilliant cream-colored star as it rises in the southeast around 11 pm on the 1st of June, and by 9 pm on the 30th. Jupiter stands against the backdrop of the much more distant stars of Sagittarius, as it has since the beginning of this year. Until the start of May, Jupiter had adorned the morning sky, but it is now about to make a dramatic entrance into the evening sky. Jupiter will reach opposition with the Sun early next month, when it will be closest to Earth and visible all night. A small telescope will easily reveal Jupiter’s brighter moons and perhaps also its cloud bands and famous Red Spot.

Mercury reaches inferior conjunction with the Sun on the 7th, and remains lost in the Sun’s glare until late in June. By the end of the month, however, Mercury will become visible low in the morning sky, and can be glimpsed in the east-northeast within an hour before sunrise. Venus has dominated the early morning sky since last autumn, but on the 9th of June it reaches superior conjunction with the Sun, and is virtually lost in the Sun’s glare all month. Venus will begin to reappear low in the evening sky in late July or early August, but will not become really prominent again until the end of October.

For more information on astronomy and weather, visit the Widener University Public Viewing Website at http://www.widener.edu/stargazing/, then click on Web Links & Resources.

A set of free sky maps can be obtained at http://www.skymaps.com/

Notes from the Astronomy Underground: Unappreciated Topics in Astronomy Part IV

Black Holes. Gamma-ray bursts. The hunt for extrasolar planets. Cosmology and the grandest scales of the cosmos. These are the fields of astronomy with the glitter and sweeping majesty of The Big Picture; sexy fields so infested with the most impressive contemporary buzzwords that NSF funding will chase you down like a pack of rabid ferrets should you show the slightest desire to work in them. But what about the other fields and attendant scientists, the ones that prefer to linger in relative obscurity, the ones to whom you could imagine all the other astronomers awkwardly crooning Bette Midler’s Wind Beneath My Wings?

Well, don’t actually imagine that. Trust me, it gives you really weird nightmares.

Anyway, it’s in honor of these thankless men and women of science I present:

Unappreciated Topics in Astronomy Part IV: Star Formation

The Job Description

Stars are kind of an important part of astronomy. A shocking revelation, I’m sure, but it’s true. Decades of relentless stellar observations and increasingly intricate computational models have provided astrophysicists a reasonably complete understanding of how these things work. And by “reasonably complete,” I mean “shamelessly superficial.” Don’t get me wrong- the voluminous body of mathematically abstruse literature we’ve compiled over the years is astonishingly complicated and would make any respectable brain wet itself in terror. But in reality, what we know of the underlying physical processes in stars is only a first-order approximation. Much like how my eyesight without my glasses is a shaky window to what’s really happening in the world. And like astrophysics research, I have no idea where I’m going, I run into walls, and I curse a lot.

But here’s the problem. As much as we astronomers pat ourselves on the back for unraveling these cosmic mysteries as best we can, we really aren’t sure how these objects actually got here. And it’s not like we can sit back and watch a comically archaic video on Our Changing Bodies for stars, either. As fun as that would be.

Now Timmy, when two giant molecular clouds love each other very much…

Of course, Creation “Scientists” might have an easy solution to this problem, one that I imagine involves a static, 5000 year-old universe, Abraham and Noah riding on dinosaurs like in they were Clydesdales, and nearly every prominent biblical figure looking suspiciously like Charlton Heston.

To be fair, early secular hypotheses concerning star formation, while they did not avoid the issue, were equally sketchy. Though Rene Descartes’ Theory of Vortices in 1644, and later Emanuel Swedenborg’s 1734 Nebula Hypothesis had some good basic ideas about stars forming from swirling, collapsing nebulae, they lacked the mathematical rigor and observational backbone that are the hallmarks of modern science.

Or domesticated dinosaurs a la Flintstones and a brazen indifference to physical reality, if you subscribe to the other school of thought.

Later on, Immanuel Kant and Pierre Simon de Laplace’s independent Nebular Hypotheses refined that idea by invoking the conservation of angular momentum to picture such a nebula rotating and contracting into protostellar disks. But our fundamental, modern conception of stellar genesis was established in the early 20th century by James Jeans. According to him, in the constant war between thermal pressure (how warm something is) and gravity, an interstellar cloud won’t collapse into a star unless its contents are sufficiently chilled. Like Coors’ Silver Bullet commercials chilled.

Of course, not all stars are the same, and there are some important differences between so-called “early” and “late” type stars.

To review, early type O, B, and A stars are like the bloated, drunken frat boys of the universe. They’re big, loud, obnoxious, and their lifetimes are proportional to these guys’ longevity in college. They also end their careers in an explosive, destructive milieu, much like what happens when setting off fireworks in the University president’s house inexplicably seems like a good idea to DKE house.

I don’t think these types of stars call each other nonsensical, asinine names like “Broseph, or “Brahzasaurus,” though.

Meanwhile, there are also the late types, the smaller, cooler F, G, K, and M stars that conserve their energy and make it all the way to graduation. Quiet, unassuming grad students fall into the far end of this spectrum, depressingly sticking around academia for years and years…

And years.

These stars also take a good hundred million years or so to get started, unlike the short hundred thousand years or so their more energetic relatives require. You might expect the more luminous, boisterous early types to show up to the star formation party first, shotgun some ISM, and trash the place before the other stars show up. This will have some significant consequences later.

Meanwhile on the observational front, the wildly popular multiwavelength approach has enjoyed a broad application to understanding how star formation works. For stars around the size of our sun, an upcoming article in The Solar System summarizes some recent highlights:

Radio observations of the M20 nebula provide images of many stages of stellar evolution, from the parent cloud, fragmentation, collapse, to emission nebulae lit by the first generation of high mass stars. The 1970’s and 1980’s saw the discovery of lower and lower mass protostars closer and closer to the Solar System. For example, IRAS measurements identified Barnard 5, a currently forming solar-type star. Radio and infrared observations of hydrogen and carbon monoxide have found 100 km/s winds, as well as expanding knots of water and bipolar radio jets characteristic of protostars. At higher energies, Chandra, XMM-Newton, and Einstein Observatory X-ray satellites have also observed nascent solar-type stars and star-forming regions for clues to our sun’s past.

Check it out. I’m using bona fide quotations here. It’s like I’m trying to make this column passably respectable and not an angry tirade of barely substantiated hyperboles or something.

Anyway, X-ray observations are the newest addition to this science, one that’s paradoxically an increasingly big deal here at Penn State, but not ubiquitously known to the Real World. According to Amanda Martin, a fellow grad working on such a project, “a typical project in [this] field would be to collect X-ray photons from a space telescope such as Chandra or XMM on a massive star formation region.” Moreover, “these regions are typically less than 5 million years old so that we can study the evolution of even the most massive stars, which are measured to be 60 times the mass of our Sun.”

Dozens of these regions are scattered throughout the galaxy, but they’re too distant to resolve anything but the largest stars. Before any conclusions can be made about X-ray luminosities of these objects, astronomers (or rather, their servile grad students) have to sift through all the photons and determine whether they came from the fetal star, a background galaxy, a foreground source, or some freak cosmic ray. “There is some form of art to this pruning of photons,” explains Amanda, “because sometimes a source will just emit a few photons at one time and then be quiet. These are variable sources that are extremely interesting to us and thus shouldn’t be thrown out.”

From there, a bunch of scientific objectives are available. For instance, a current topic of interest is studying the effects that quickly forming massive stars have on the evolution of more leisurely-forming ones and their protoplanetary disks. These disks, the precursors to extrasolar planets, were previously identified in infrared studies.

“These massive stars are emitting a lot of stellar radiation which cooks and evaporates the disks of nearby stars. With the x-ray source data we can do a statistical significance test to see if those less massive stars around larger stars are less likely to have disks, and later planets.”

Why No One Likes It

It would be nice if this Jeans business was the only pertinent criteria for star formation. It would also be nice if George Lucas didn’t go unambiguously insane and make another Indiana Jones movie. But we don’t live in a perfect world.

Way to ruin yet another franchise, George.

Carl von Weizsacker and Dirk ter Harr in the mid-20th century crashed the party by introducing supersonic turbulence into the mix. Along the way, some other scary-sounding concepts emerged like Alven waves, magnetohydrodynamic turbulence, ambipolar diffusion, and a lot of other nasty-sounding magnetic effects we’d prefer to ignore like the current administration ignores polar bears in its environmental policies.

Lacking the computational ability to address these issues, astronomers could pretty much ignore all these problems for 50 years, focusing hardware and software development on better iterations of Oregon Trail and Q*Bert. But now in the 21st century, we really have no excuse. We tried to ford the river, the oxen died, we shot up 8,000 pounds of pixilated Buffalo, Jebediah suffered a slow and agonizing demise from dysentery; it’s time to move on.

This is the main reason why not a whole lot of people like this field. It’s new. It’s poorly understood. It’s hard. In that sense, this is the epitome of science just not being that transparent to the public. It’s all abstract and terminally stricken with incomprehensible jargon. Frankly, that’s all the more reason why people should respect it more.

X-ray studies fare even worse in that regard, since it’s rather counter-intuitive. These energetic photons are normally attributed to equally energetic processes like supernovae or active galaxies, not from the low energy environments needed for gravity to work its magic and turn interstellar refuse into a new star. On the surface, this seems to make as much sense as the soundtrack to Footloose.

I mean, it’s great you’re holding out for a hero, Bonnie Tyler, but they’re racing tractors. In Iowa.

Needless to say, this is all still a work in progress.

Who Does This Stuff?

Anyone working in this field has to be comfortable with the sometimes aggravating minutia of data reduction and all its implicit uncertainties. As with any subfield of astronomy, you have to know your equipment just as well as you understand the physics of whatever you’re trying to study.

Or if you’re in grad school, confidently dance around actually understanding said physics and try to steal stuff from the supply closet.

How is this any different from the astronomers I’ve described in previous updates to this tired series on the overlooked sciences? In a lot of respects it’s not; I’m just running out of ways to rephrase the same sycophantic spiel. I guess the salient difference here is that when you get the data from Chandra or XMM, you really don’t know what you’re going to get out of them. Will you have the requisite sensitivity to see solar-type stars? Will your resolution be adequate to pick out binaries? Will you finally figure out why everyone in America loves The Princess Bride even though it’s probably the most unimpressively mediocre comedy ever made?

This kind of primetime game show uncertainty is part of the appeal to star formation research. In terms of the proverbial Big Picture, these studies also have an unspoken effect on the dramatically philosophical Life in the Universe debate. Our current understanding of the Drake Equation frames this issue in a pretty despondent light already, i.e. we shouldn’t expect to make timely contact with the possibly mere handful of extremely remote civilizations in our own galaxy. But in consideration of the deleterious effects rapidly forming early type stars have on struggling protoplanetary disks of their diminutive neighbors, the odds are weighed even more against striking up cordial small talk with the extraterrestrial Joneses. How often can you say that your job lets you make grandiose conclusions about the privileged isolation of mankind and the underlying anthropic nature of the universe?

I don’t know if I like the idea of our species being somehow uniquely special, though. It makes me wonder whether drinking Saranac and watching Three’s Company on Hallmark at two in morning is an ideal use my time.

Eh, who am I kidding? Don Knotts is hilarious.

Notes from the Astronomy Underground: Unappreciated Topics in Astronomy Part III

Well, don’t actually imagine that. Trust me, it gives you really weird nightmares.

Anyway, it’s in honor of these thankless men and women of science I present:

Unappreciated Topics in Astronomy Part III: Instrumentation

The Job Description

Well, I’ll be perfectly honest- this particular field is way beyond my expertise. In fact, I misspelled “Instrumentation” the first time I wrote it here (I guess it didn’t really have a silent q after all). Even worse, the last time I had any hands-on experience with components of the scientific method that weren’t ones and zeroes floating around the bloated innards of a Linux machine was the Electronics & Instrumentation class I took as a junior in college. And I’m not going to say it was a complete disaster, but the only useful thing I built the whole semester was a pretty sorry-looking and blatantly illegal beer quality tester.

That, and a few fires from slovenly, piecemeal circuits, actually. I was politely advised to pursue more promising career avenues after that. Something about making the lab smell like twisted metal and a southern Pennsylvania American Legion outpost at 3 in the morning.

Anyway, I’ll give you a quick run-down of what I know.

Over in optical/infrared (lR) land, instrumentalists are in charge of designing and building the reliable, amazingly efficient CCD cameras and spectrographs that allow the rest of us to unabashedly make all these amazing claims about the star formation properties of galaxies millions of light years away, abundances of elements, dust grains, and all sorts of crazy molecules in space. Even more incredible is that we’re just starting to get a feel for the compositions of extrasolar planetary atmospheres and can speculate a little less wildly about the prevalence of life in the universe.

And actually, all this is even harder than it sounds, especially for long wavelength observations where practically everything around you (including the atmosphere and the telescope itself) emits radiation in the wavelength range you want to observe. On top of that, detector response gets all screwy and nonlinear, with each individual pixel having its own time- and temperature-dependent properties.

Sure, you can strap your IR telescope onto a rocket and launch it into space like astronomers have done for Spitzer and Hubble, and will follow up for the upcoming James Webb Space Telescope. That one’s boasting a pretty impressive resume with the Near-IR Camera, Spectrograph, and Mid-Infrared Instrument. We’re talking a 4096 x 4096 pixel imager, a spectrograph with a malleable array of 64000 microshutters to select individual objects for study from a 3.4’ x 3.4’ field of view, and a composite camera/spectrograph that combines the best of both imaging and spectroscopic worlds.

That is a lot of intelligent-sounding specs. But personally, I’m still a bit uneasy about working with a telescope named “Jimmy,” of all things.

Let’s not forget that we need to cool down the whole telescope to eliminate that pesky thermal emission, too. Chilling a telescope to a few degrees above absolute zero, with the sun’s unmitigated radiation bearing down on it the whole time? This stuff sounds as hard as sitting through the last 20 minutes of the past week’s The Office finale. I still haven’t forgiven Ed Helms for what he did.

Ok, it’d be easier and more cost-efficient to keep your equipment on the planet, but for IR it’s best to get above that noisy water vapor in the atmosphere. The folks working on SOFIA seem to have come up with kind of a bizarre compromise- they put a whole telescope on a plane. Ignoring the logistics of getting the thing to track and focus while situated uncomfortably close to a jet engine, I’d still be worried about having to sit next to a colicky baby or that really gross sweaty guy that wheezes a lot during an observing run. Not to mention all the time lost by getting stuck at O’Hare and taxing the runway for days.

I’m also tempted to make a pithy Snakes on a Plane reference here, but I don’t think I’m allowed to swear like that in a public forum.

Over on the high energy side of the spectrum, one of my friends and fellow grad here at Penn State is working on an X-ray detector that will have a couple of advantages over the current generation of CCD-style detectors currently in use. As with optical CCDs, instrumentalists are always looking for ways to get the chip to “read out”- spit its data at the receiving computer- faster. They’re also trying to siphon off this information from different parts of the array at varying rates. All of this while still keeping the reliable resolution and low electronic noise the devices have now.

Why is this such a big deal? Reading out the chip can take up a lot of valuable time, especially if you’re a satellite that’s got a full schedule of observing ahead of you until your cryogens or power inevitably run out. And if you’re a person, well, then you get to stay on Earth and do fun things like go to the IHOP and eat pancakes. Of course, if I had my way, all these monumental technological advancements to solid state arrays would invariably include pancake-making as a fundamental design requirement. I’m really quite shocked that no one agrees with me on this. Come on. A state-of-the-art CCD chip that cooks you breakfast every day. In space. That would be awesome.

As with all fields of astronomy, Instrumentation would be nothing without the unnavigable myriad of oppressive federal bureaucracy making you beg like a dog for every penny you earn. Unlike the projects I’ve worked on, where you just need to justify telescope/satellite time and student manpower squandered on Minesweeper and YouTube, instrumentalists need some serious money and high-tech equipment to build their increasingly complex and sensitive detectors. I mean, as impressive as the Professor was on Gilligan’s Island, you really can’t fashion a CCD chip or spectrograph solely out of coconuts and palm leaves. Granted, MacGyver can, but I don’t think Richard Dean Anderson does that kind of stuff anymore.

In reality, “small” projects with an employ of a handful of personnel can take advantage of programs like SMEX that scrounge up the meager few millions needed for resources and salaries. It seems like a lot of money, but this is actually the low end of funding requests, for projects purchasing instruments for analysis that have already been made.

It gets complicated for the bigger projects. According to my sources, “a larger project pools together multiple organizations into a consortium who each give money and manpower.” Sounds like a diabolical amalgam of Terry Gilliam’s Brazil and every legitimate concern about heartless corporations raised by big haired pop bands of the 1980s, doesn’t it?

Yes, I’m listening to We Built this City by Starship right now. No… no, I’m not proud.

Why No One Likes It

I think it’s a fair assessment that a lot of astronomers don’t really care so much about how data are obtained, just as long as it gets done. I’m very guilty of that. As long as the data end up on my computer, I don’t care if they’re delivered by a team of highly trained experts or Ed McMahon flanked by a squad of parachuting circus bears.

Actually, I think I’d like the last option better. There’s something about skydiving bears and Star Search that’s just so inexplicably appealing.

The bottom line is that Instrumentation as a field is only transparent when something goes wrong. Remember what happened to the Hubble telescope? That whole mess about spherical aberration and fuzzy images and all that? Never mind that the technicians got the mirror ground perfectly to an accuracy of 1/800,000th of an inch, but everybody went all Tom-Cruise-is-a-Scientology-Spouting-Nutcase crazy when it didn’t work quite right. It’s almost like we all just forgot about the scientific method and replaced the “take replicable, precise measurements” part with “and then magic happens.” It’s kind of ironic, especially when we’re always up on our soap boxes about the unquestionable importance of science as civilization’s greatest intellectual movement.

So really, on a scale from “grad student” to “fluorescent light bulb,” instrumentalists fall somewhere in that depressing middle region in terms of public and academic appreciation. And to be clear, “grad student” is the low end of the scale, not the high end.

Who Does This Stuff?

It kind of seems like the underlying theme in this series of Articles on Parts of Astronomy People Should Respect or at Least Be Vaguely Aware Of is that working in such a publicly marginalized subfield requires an innate self-motivation that borders on the clinically insane. Now that may also be a consequence of my ever-unbiased and professional journalistic flair, but in this case it’s true. How deeply absorbed are instrumentalists in their work? Well, if you checked that SMEX website, you might notice that these guys are so busy that they haven’t updated their website since 1999.

Which is pretty cool, actually- it feels like you’ve opened up an esoteric internet time capsule or something. Almost makes you nostalgic for Y2K, unregulated music piracy, and a functioning economy.

But seriously, instrumentalists are a special breed with complimentary interests in science and the technological process that stimulates it. In practice, understanding both the engineering of astronomical detectors and the science they’re designed to do put this hybrid engineer/scientist species in an ideal position to build the best equipment possible. Which is good, since finagling a handful of photons out of a brutal cacaphony of atmospheric and thermal emission is not exactly trivial. Unsatisfied with blindly accepting the apparent magic of data acquisition, these valiant men and women are the true epitomes of the meticulous Scientist the rest of us only pretend to be.

So, instrumentalists of the world, if I ever see you at the bar, next round’s on me. Just… no fancy mixed drinks, please. I’m not made of money, here.

Notes from the Astronomy Underground: Unappreciated Topics in Astronomy Part II

Well, don’t actually imagine that. Trust me, it gives you really weird nightmares.

Anyway, it’s in honor of these thankless men and women of science I present:

Unappreciated Topics in Astronomy Part II: Optical Variability of Quasars

The Job Description

Quasars are the distant lighthouses of the universe; galaxies whose central black holes have kicked into gear and started playing a cosmic game of Hungry Hungry Hippos © with the material around them. It’s a fascinating topic, sure, but all we see from earth are the luminous jets the black holes expunge perpendicular to their host galaxies, light that at first glance looks like it came from an ordinary star. In my experience, it’s pretty anticlimactic to see what a quasar actually looks like from here, especially if you have to do it every day for fifteen weeks.

I had the indescribable pleasure of this job for a whole summer some years back as a carefree, neophyte undergrad at Colgate University. And I never felt appreciated, either, so that’s part of my motivation for whining about it now. The other part is simply that this line of work is grueling- you observe all night, AND you have to go into work the next day to analyze the data, leaving you a pale, drooling, and constantly jetlagged shell of a human being by the end of the project.

Ok, it’s not all that bad. But it is a harsh lesson in the bitter reality of scientific repetition, replication, and perseverance, which, if there’s anything I want to impress upon our society, it’s that. Here’s a quick look of a typical night’s observing run, as well as I can recall:

8:30 pm: Ride Bike to Observatory. Avoid getting hit by glass bottles hurled by roving caravans of restless, angsty teenagers. Apparently Upstate New York degenerates into a Mad Max sequel when the sun sets. Outrageous Australian accents and everything. Must be the gas crisis.
9:00 pm: Arrive at observatory. Record various temperatures from thermometers stationed at a variety of locations around the main building (this is important for estimating weather-related measurement errors). Hit head multiple times on low-lying tree branches. Swear audibly.
9:30 pm: Unsheathe telescope aperture; move instrument into position, insert R-band filter, and turn on CCD. Adjust Dome slit, and wince as its unlubricated movements make the sounds of a thousand mangy cats getting fed to a wood chipper.
10:30 pm: Retreat to Warm Room. Try to find 1st target object multiple times. Frustratingly stare at a computer screen of what appears to be a bunch of randomly-distributed stars. Grapple with feelings of resignation and profound intellectual inadequacy. Finally locate object two minutes before it dips below horizon. Again, swear audibly.
12:00 am: Run upstairs to set dome and telescope for next object.
1:00 am: Take several 2-5 minute CCD exposures. Also record dark current and bias. Play Frogger on other computer while chip integrates.
1:10 am: Run upstairs and change filter.
1:25 am: Realize in horror you put in the wrong filter. Desperately run upstairs to replace it. Trip and lacerate right knee on the way down. Swear audibly. Hope last tetanus shot is still good.
2:00 am: Resume observations. Control bleeding and try to formulate a convincing argument for why Mac and Cheese is really just “pasta nachos.”
2:20 am: Get very confused when the last series of images comes up fuzzy. Go outside to a photometric, crystal clear night… with the exception of one punk cumulus cloud where the telescope is pointing. Swear very audibly. Then sprint back inside when angrily awakened university president turns on the lights in her neighboring house.
2:30 am: Explain to Campus Safety that there is no domestic disturbance at the Observatory. Promise you’ll be quieter in the future. Repeat 10:30 pm- 2:30 am routine.
6:00 am: Bike downhill in impenetrable fog. Silently pray there are no meandering deer or oncoming traffic at this hour.
The Next Day: Dejectedly try to explain to advisor why you didn’t get nearly enough data last night. Predictably, he is not in favor of your “pasta nachos” theory.

What’s the point to all this abject suffering? In this game, you’re trying to track the activity of a quasar in time. Every 5-minute observation gets sent through a complex maze of data reduction and calibration, then plunked onto a plot of magnitude vs. time (i. e. a “light curve”). It sounds simple, but it’s an intricate combination of fickle computer code and precisely coordinating the times to a universal standard. You also need to hunt down other groups’ data, and figure out how their magnitude or flux measurements scale to your own (a nontrivial task). When that’s done, you compare how brightness fluctuations in one filter compare to measurements in another, and assign a “spectral index” that defines how the shape of the continuum in the optical region changes with these fluctuations. You can also compare specific magnitudes to colors, check variability over different timescales, and pretty much generate as many graphs as you want until the cows come home.

That cliché is appropriate, actually, albeit somewhat anachronistic. See, I went to school in upstate New York. There were cows everywhere.

Then, you might look into how optical variability compares to measurements other astronomers have made in the radio, infrared, UV, X-ray, or gamma-ray wavelengths. Why go through that extra trouble? Think of the spectrum of a quasar as a great Romantic-era symphony. If you restrict your reception of this masterpiece to a single octave- much like only observing in one wavelength range- then you might hear something that sounds more like a chorus of angry crickets than palatable music (Thanks to David Hefland for that analogy).

This is particularly important for blazars, the subset of the quasar family that doesn’t display prominent emission or absorption features in its spectrum. We think this is because their optical/radio jets are preferentially directed in our line of sight, practically blinding us to the host galaxy’s own emission. The light we receive can also take a more circuitous journey, getting bumped up in energy from collisions with electrons spiraling around the central accretion disk, and scattering through a whole bunch of clouds of galactic junk. All these effects can be seen by looking at the whole spectrum, from radio to gamma-rays. Ultimately, the main reason why astronomers record a blazar’s variable history is so we can pin down the timescales of flaring events, how they appear in different wavelengths, and how they compare to models of these objects. There’s a lot of physics going on here- people have been observing quasars for over 40 years, and we’re still trying to piece together their story.

Why No One likes it

That’s probably an unfair section heading. After all, I’m in a department full of AGN fanatics that would claw out my pancreas if they knew I was bad-mouthing quasars.

I’m assuming at least one of them knows where the pancreas is. I sure don’t.

But in all honesty, optical variability research is the least glamorized aspect of all extragalactic studies. For one thing, there’s that awful mess of corrections that have to be made for instrumentation response and atmospheric conditions. I hope my last post fluidly made the point that this process is just bad news bears for anyone. But the big problem with optical observations, paradoxically enough, is that it’s so “easy” (read above nightly itinerary for clarification) to make them.

Unlike radio and more energetic wavelengths like X- and gamma-rays, observations in the optical spectrum don’t require exhaustively scheduled time slots on large radio dishes or orbiting satellites. If you want observe a sufficiently close quasar, say at a redshift of 0.1 or so, and you have your own telescope, you can observe pretty much whenever you want. This is unlike high energy-observatories like Chandra, where there’s always a month-long waiting list and you need exorbitant integration (exposure) times to collect enough photons for each observation.

I guess it would be akin to the differences between your friendly neighborhood bar and some upscale New York night club. The former is your regular and familiar place you can always rely on (and no, I haven’t been watching Cheers reruns on Nick at Nite). Nothing too remarkable. The latter, meanwhile, is an expensive, high-profile, energetic social scene with a huge line to get in and a bouncer that can turn you down for seemingly arbitrary reasons.

Except in this case, the bouncer is the committee in charge of allocating telescope time (a group of people who generally have very different physiques and personalities). Also, there aren’t a whole lot of shady people snorting lines of coke in the bathroom. Presumably.

Anyway, this is an obvious obstacle if you want to know what’s going on with a quasar on an hourly basis. Basically, optical wavelengths provide the most accessible, quickest avenue for investigating short-term variability of AGN. And, well, someone has to do it.

Who Does this Stuff?

This research seems to be mainly the domain of small, Northeast liberal colleges that want to stay competitive with larger institutions by claiming legitimate, in-house research contributions to a variety of fields. Optical variability studies are one of the few opportunities for undergrads to engage in hands-on observations of the types of extreme extragalactic phenomena that sound pretty neat in a pamphlet. Why not radio or near-infrared studies? The weather up here is pretty uncooperative, and our elevation isn’t high enough to get above a lot of pesky water vapor.

As for the grownups behind the science, practitioners of this craft are like Astronomy’s Arrested Development. They’re quirky, intelligent people that America unfortunately doesn’t pay a whole lot of attention to. Small schools like Colgate pride themselves on employing excellent educators as well as researchers, so the faculty must strike a balance between powerhouse researchers and mentors with saintlike patience. It takes a man or woman of extraordinary caliber to simultaneously publish reputable scientific accomplishments and explain to hordes of clueless undergrads for the umpteenth time that no, you really shouldn’t try to light ants on fire with the telescope mirror.

But most importantly, you need what my old advisor called “The Passion-” the single-minded drive to observe all night and analyze your data or teach all day. While any other conventional astronomer would consider this ineffable devotion a borderline neurotic overkill of the scientific process, Optical Quasar Variability Guy just calls it a normal day. In fact, I once asked my advisor what kept him motivated to endure ruthless New York winters and the long hours to slave away at a low-profile branch of astronomy, and he told me that he’d quit if there was someone else out there that could do what he does. That, my friends, is a display of some serious astronomical cajones.

And it’s also an excellent example of a Data Junkie- the kind of person who uncontrollably itches like a crack addict if he can’t get his next research fix. Sustained by a winning combination of caffeine, adrenaline, and an inhuman hunger for new information, the Data Junkie and his seemingly unlimited supply of saturated external hard drives is an admirable paragon of what tenacious men and women of our noble pursuit can accomplish. I swear, these people are so addicted, they would gnaw off one of their own limbs if they got caught in a bear trap on their way to work. But that’s what makes them so irreplaceable.

It is to you, Quasar Optical Variability Guy, that I offer this week’s heartfelt salute.

Notes from the Astronomy Underground: Unappreciated Topics in Astronomy Part I

Well, don’t actually imagine that. Trust me, it gives you really weird nightmares.

Anyway, it’s in honor of these thankless men and women of science I present:

Unappreciated Topics in Astronomy Part I: Standard Stars and Magnitude Calibrations

Ah, magnitudes. Perhaps nothing embodies our noble science’s absurd affinity for nonsensical units of measurement like this archaic, backwards, and nonlinear scale for categorizing apparent stellar brightnesses. Maybe it’s because we like to confuse irritable physicists, but for some reason astronomers have stuck with this bizarre system since Hipparchus trained his eyes to the sky Back in the Day.

Author’s note: Back in the Day = 2100 years ago.

Or maybe it’s because we’re always eager to classify things before we have any idea what’s actually going on. How else do you explain why there are predominantly early-type stars in late-type galaxies, and vice versa? Yeah, it takes a while to get used to.

But these numbers don’t just come out of nowhere, right? Well, actually, they do. Magnitudes are an arbitrary numerical description of a star’s brightness as seen from earth, but it’s a self-consistent, arbitrary system that has to reference both the physical reality of the star and the telescope, camera, CCD array, filter set, llama, whatever, that you’re using.

But just for the record, llamas make terrible astronomical detectors. They get spit everywhere.

The Job Description

Establishing a magnitude system requires a network of standard stars to which you can compare your observations. We like to start with Vega- it’s big, pretty, and according to Carl Sagan, it’s prime real estate for extraterrestrial communications industries. Only problem here is that, not only do you need to take your detector’s response to starlight into account for looking at this star (which, if you observed in the era where polio was all the rage, was probably frustratingly nonlinear and a real pain to figure out), but you need to carefully measure the continuum of Vega against some conditioned laboratory standard. Which means you need to know every little seemingly trivial technical aspect of this other apparatus as well. What’s even worse is that Vega may be a low-level variable, dust-enshrouded star with a correspondingly schizophrenic continuum. Not to mention there’s that whole “atmosphere” thing that gets between you and whatever you’re looking at. Getting rid of this in your measurement involves a tricky slew of wavelength-dependent factors like the star’s output flux, the airmass blocking your view, turbulence and weather-related problems, etc.

That’s especially important for the secondary star network I mentioned before, where the amount of air in your way and its extinction properties depend on where you look in the sky. Yet another issue lies in selecting the right stars for this business. Not every star is the same, and differences in composition and the absorption lies that come out in their spectra make a huge difference.

This is all well and good, but you just can’t stare at something and expect to get anything really interesting out of it (unless it’s a rerun of the old Adam West Batman series… I just realized Burgess Meredith was the Penguin! That’s pretty awesome). You have to sample the light in a couple of different parts of the spectrum with some filters, and compare results in each measurement. Producing filters to represent physically important phenomena is an equally a daunting challenge as transforming measurements made in one system to an entirely different one. This process is not exactly comparing apples to oranges, but rather comparing apples to other apples made half-way around the world with different soil, water, amounts of sunlight, everything. And you have to have faith the other guys (or their clueless, bumbling grad students, most likely) didn’t screw up some minute detail along the way.

Why No One likes it

In my opinion, doing this research is about as exciting as watching paint dry. But unfortunately, this would be the kind of paint that’s so undeniably important that, if someone doesn’t watch it, it’ll erupt into leaping flames and take out twelve city blocks. Your community is razed to a dystopian landscape of desolate, inhospitable ruin for decades, all because no one wanted to do one mind-numbingly boring task.

For astronomy, any measurement of any kind of perceived brightness (which for us is every measurement), be it from a star, galaxy, quasar, or what have you, would be rendered utterly worthless. And all our explanations of the underlying physics in all these objects would follow suit. No spitting llama telescope could circumvent this disaster.

Who Does this Stuff?

So what kind of person could possibly be attracted to such a thankless existence so fraught with agonizing observational minutia? Have you ever taken a class from someone who took off an inordinate amount of points on a homework assignment just because you dropped the eighth decimal place, or ignored some superficial process that contributes a measly 0.5% error? Yeah- it’s That Guy. But That Guy, as absolutely grating as his single-minded devotion to superhuman degrees of mathematical precision may seem, is the backbone of the angry, charging emu that is observational astronomy.

Or spitting llama, whatever.

And it is to the valiant men and women in this overlooked field that I dedicate this blatant rip-off of Budweiser’s Real Men of Genius laudatory ballad (feel free to sing the italicized backup vocals yourselves).

So many thanks, That Guy, you obsessive compulsive, passionate mess of firing neurons.

High signal-to-noise goin’ on in your brain…

Without your overwhelming zeal for effective wavelengths, extinction curves, and detector sensitivities, all of astronomy would crumble at your feet.

Sorry, cleaning it up is a union job…

Sure, your papers will get cited fairly often, but those authors just want to apply your hard work and sacrifice to their own nefarious schemes (seriously, it’s what I do). They’d just as soon cite a chimp if it had any capacity for your difficult work.

But then everything would be in units of bananas…

They don’t care about the hours you spent poring over your setup, your equipment, your data, massaging every last bit of useful information you could from the noise, the systematic and random errors that so often threaten to paralyze your achievements.

Yeah! No more ridiculous animal analogies todaaay…

We salute you, expert photometrist and unwavering bastion of astronomy.

Mike Brown's Planets: Circular Arguments

When something exciting was happening and astronomers wanted other astronomers around the world to know, they used to send a telegram to one central location from which subsequent telegrams were then exploded to observatories around the world. The CBAT --Central Bureau for Astronomical Telegrams -- still exists today to provide the same service, except that it is all done by email today. The CBAT issues International Astronomical Union Circulars, which used to be, in fact, rectangular, approximately the size of an index card, on which new exciting information was mailed. Again, today, it is all email. The switch from telegrams arriving at observatories to emails arriving in everyones already overstuffed in box is another sign of the quaintness being snuffed out of astronomy in favor of efficiency. And I, for one, say thank goodness for efficiency.

Today, we are issuing our IAU Circular describing the moon shadows. It will read something like this:

Mutual Events of 2003 EL 61 and its Inner Satellite

Daniel Fabrycky (Harvard University), Darin Ragozzine & Michael Brown (California Institute of Technology) and Matthew Holman (Smithsonian Astrophysical Observatory)

Orbital fits to the relative astrometric positions of dwarf planet 2003 EL61 (IAUC 8577) and its inner satellite, S/2005 (2003 EL_61) 2 (IAUC 8636), have revealed a near edge-on orbit, implying likely mutual events. The orbital model was based on images from HST (WFPC2) and Keck (LGS-AO). Due to the changing orientation of the Earth-EL_61 line of sight, the orbit is moving closer to edge-on until August 2008, after which the orbit will open up again. The current distance of closest projected approach is ~500 km, nearly the same as the semi-minor axis of the triaxial primary (Rabinowitz et al. 2005, ApJ, 639, 1238), so events will likely be grazing. Shadows of the satellite and EL_61 will likely miss each other. The unocculted lightcurve has double-peaked rotational modulation of full amplitude 0.25 mag and period 3.9 hours; template lightcurves of this variation are available from Holman. The duration of the events will be between 0 and ~6 hours; ingress and egress will consist of ~0.03 magnitude changes on a timescale of ~10 minutes. Telescopes distributed in longitude are needed to follow events as the orbital period is 18.36 d. The main body is rather faint (V~17.4 mag), so high-precision photometry requires moderate (~1 m) collecting area.

Due to orbital eccentricity, events in which the main body occults the satellite are more likely to occur than events in which the satellite occults the main body. Our orbital model predicts mid-event times as follows (add or subtract up to 3 hours for ingress or egress times).

For the satellite occulting the main body:

HJD 2454617.58 +/- 0.07 = 5/31 01:50+/-1:40 UT

HJD 2454635.84 +/- 0.07

HJD 2454654.11 +/- 0.07

HJD 2454672.48 +/- 0.08

For the main body occulting the satellite:

HJD 2454625.22 +/- 0.07 = 6/07 17:10+/-1:40 UT

HJD 2454643.45 +/- 0.07

HJD 2454661.79 +/- 0.1

What does all of this mean? First, a little sadness. We missed most of the shadows by a few years. There is only a chance to observe about 3 more this year, and then not again for 130 years.

The next event is visible over Asian/Europe, but we think it is likely to just be a graze, so nothing will be clear. After that we are on to Hawaii and Japan again for June 7th.

Honestly, I think we're too late. But what a great project it will be for our great-great-great-grandkids.

Is Pluto a Planet?

"Honey,
I Shrunk the Solar System"

(NASA: Published 08.24.2006.)

"The International Astronomical Union, wrapping up its [2006] meeting in Prague, Czech Republic, has resolved one of the most hotly-debated topics in the cosmos by approving a specific definition that gives our solar system eight planets, instead of the nine most of us grew up memorizing.

NASA has already visited all eight planets that retain their official title: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. In addition, the agency has its New Horizons spacecraft en route to Pluto, which the astronomical union has re-assigned to a new category of celestial objects, to be called "dwarf planets."

"NASA will, of course, use the new guidelines established by the International Astronomical Union," said Dr. Paul Hertz, Chief Scientist for the Science Mission Directorate at NASA Headquarters. "We will continue pursuing exploration of the most scientifically interesting objects in the solar system, regardless of how they are categorized."

Ceres, which orbits in a belt between Mars and Jupiter and is the largest known asteroid, is one of those interesting objects. In 2007, NASA will launch the Dawn spacecraft on a mission to study Ceres, which the astronomers have placed in the dwarf planet category, alongside Pluto. The dwarf planet family also includes 2003 UB313, nicknamed "Xena." When Dr. Mike Brown of Caltech and his colleagues announced last summer that they'd discovered the object, which is bigger and farther away than Pluto, many astronomers decided it was time to figure out once and for all, "What exactly is a planet, anyway?"

Figure 1. Hubble Space Telescope view of Pluto. The larger view includes Charon. Image credit: ESA/NASA

Here's how it all shakes out. The International Astronomical Union has decided that, to be called a planet, an object must have three traits. It must orbit the sun, be massive enough that its own gravity pulls it into a nearly round shape, and be dominant enough to clear away objects in its neighborhood.

To be admitted to the dwarf planet category, an object must have only two of those traits -- it must orbit the sun and have a nearly round shape. And no, moons don't count as dwarf planets. In addition to Pluto, Ceres and 2003 UB313, the astronomical union has a dozen potential dwarf planets on its watchlist.

What's to become of the other objects in our solar system neighborhood, the ones that are not planets, not dwarf planets and not moons? The organization has decided that most asteroids, comets and other small objects will be called "small solar-system bodies."

Despite the establishment of these three distinct categories, there are bound to be gray areas. As technologies improve and more objects are found, the International Astronomical Union will set up a process to decide which categories are most appropriate for specific objects.

Even before the discovery of Xena, not all was calm in the planetary world. There was debate after Clyde Tombaugh discovered Pluto in 1930. With its small size, distant location and odd orbit, some questioned whether Pluto was really a planet or just an icy remnant of the planet-forming process.

That issue has been resolved by the International Astronomical Union. Among those most keenly following the debate -- Mike Brown, who has been awaiting word on Pluto and the object he found, Xena.

"I'm of course disappointed that Xena will not be the tenth planet, but I definitely support the IAU in this difficult and courageous decision," said Brown. "It is scientifically the right thing to do, and is a great step forward in astronomy."

Although the revamping of our solar system might seem unsettling, it's really nothing new. In fact, when Ceres was first discovered in 1801, it was called a planet, as were several similar objects found later. But when the count kept on growing, astronomers decided "enough is enough," and they demoted Ceres and its siblings, placing them in a new category, called asteroids.

The International Astronomical Union, founded in 1919, assigns names to celestial bodies."

(From NASA's "Honey, I Shrunk the Solar System" Published 08.24.2006. - Montage of planets. Image credit: NASA/JPL)

For more information, please visit:
The International Astronomical Union or IAU General Assembly 2006.
Press Releases During IAU General Assembly 2006.

Final IAU Resolution on the definition of "planet"

RESOLUTIONS:

Resolution 5A is the principal definition for the IAU usage of "planet" and related terms. Resolution 5B adds the word "classical" to the collective name of the eight planets Mercury through Neptune.

Resolution 6A creates for IAU usage a new class of objects, for which Pluto is the prototype. Resolution 6B introduces the name "plutonian objects" for this class. The Merriam-Webster dictionary defines "plutonian" as:
Main Entry: plu • to • ni • an
Pronunciation: plü-'tO-nE-&n
Function: adjective
Usage: often capitalized
: of, relating to, or characteristic of Pluto or the lower world

After having received inputs from many sides -- especially the geological community -- the term "Pluton" is no longer being considered.

IAU Resolution: Definition of a Planet in the Solar System

Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation 'planets'. The word "planet" originally described "wanderers" that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information.

RESOLUTION 5A
The IAU therefore resolves that planets and other bodies in our Solar System, except satellites,be defined into three distinct categories in the following way:

A "planet"¹ is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape², (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
All other objects³, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

¹The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
²An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
³These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

RESOLUTION 5B
Insert the word "classical" before the word "planet" in Resolution 5A, Section (1), and footnote 1. Thus reading:
(1) A classical "planet"¹ is a celestial body . . .
and
¹The eight classical planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

IAU Resolution: Pluto

RESOLUTION 6A
The IAU further resolves: Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

RESOLUTION 6B
The following sentence is added to Resolution 6A: This category is to be called "plutonian objects."

Disclaimer: This article is taken wholly from, or contains information that was originally published by, NASA and International Astronomical Union. Topic editors and authors for the Encyclopedia of the Cosmos may have edited its content or added new information. The use of information from NASA and International Astronomical Union should not be construed as support for, or endorsement by, that organization for any new information added by EoC personnel, or for any editing of the original content.