Cosmos Website: Blog

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 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 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.

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 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 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.

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 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.

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.