The Night Sky: October 2008

Contents

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.

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