Non-Profit Internet Source for News, Events, History, & Culture of Northern Frederick & Carroll County Md./Southern Adams County Pa.


The Night Sky of December

Dr. Wayne Wooten
Professor of Astronomy

For December 2014, the Moon will be Full Moon, the Long Night Moon, is on December 6th. The waning gibbous moon passes five degrees south of Jupiter in the morning sky on December 12th, and will interfere to some degree with the peak for the Geminid meteor shower on the following morning before dawn. The last quarter moon occurs on December 14th. The winter solstice occurs at 6:03 PM on December 21st, and winter begins on the shortest day of the year. The new moon occurs on December 22nd. The waxing crescent moon passes six degrees north of brilliant Venus on December 23rd, then five degrees north of fainter reddish Mars in the SW twilight on Christmas evening. The first quarter moon follows on December 28th.

Venus returns to the evening sky during the first two weeks of December. She is coming from the far side of the Sun, and shows a tiny, almost fully lit featureless disk in the telescope, but will get much higher in the evening sky during the first half of 2015. Mars remains in the evening sky this month, moving through Capricornus in SW twilight. Jupiter dominates the evening sky for the next five months, brighter than any other planet except Venus and imbedded among the stars of Leo.

Jupiter reaches opposition in February 2015. Any small telescope will show the four large Galilean moons around at 10X or higher power, but larger scopes will be needed to show the famed Great Red Spot, which seems to be shrinking currently. Saturn rises about 4 AM in Scorpius, and the famed rings are now open about 22 degrees. They were edge on as seen from the Earth in 2009, and will be tilted 27 degrees toward us at solstice in 2017, when they will double the planetís present brightness.

The square of Pegasus dominates the western sky. The constellation Cassiopeia makes a striking W in the NW. She contains many nice star clusters for binocular users in her outer arm of our Milky Way, extending to the NE now. Her daughter, Andromeda, starts with the NE corner star of Pegasusíí Square, and goes NE with two more bright stars in a row.

It is from the middle star, beta Andromeda, that we proceed about a quarter the way to the top star in the W of Cassiopeia, and look for a faint blur with the naked eye. M-31, the Andromeda Galaxy, is the most distant object visible with the naked eye, lying about 2.5 million light years distant. Overhead is Andromedaís hero, Perseus, rises. Between him and Cassiopeia is the fine Double Cluster, faintly visible with the naked eye and two fine binocular objects in the same field. Perseus contains the famed eclipsing binary star Algol, where the Arabs imagined the eye of the gorgon Medusa would lie. It fades to a third its normal brightness for six out of every 70 hours, as a larger but cooler orange giant covers about 80% of the smaller but hotter and thus brighter companion as seen from Earth.

Look at Perseusí feet for the famed Pleiades cluster; they lie about 400 light years distant, and over 250 stars are members of this fine group. Bob Gaskinís photo reminds us the "Seven Sisters" are probably the most beautiful objects in the sky in binoculars, with over 100 members of the cluster, as well as clouds of gas and dust the young cluster is now moving through, visible. East of the seven sisters is the V of stars marking the face of Taurus the Bull, with bright orange Aldebaran as his eye. The V of stars is the Hyades cluster, older than the blue Pleaides, but about half their distance. Their appearance in November in classical times was associated with the stormy season, when frail sailing ships stayed in port. Aldeberan is not a member of the Hyades, but about twice as close as the Hyades; distances in astronomy can be deceiving.

Yellow Capella, a giant star the same temperature and color as our much smaller Sun, dominates the overhead sky. It is part of the pentagon on stars making up Auriga, the Charioteer (think Ben Hur). Several nice binocular Messier open clusters are found in the winter milky way here. East of Auriga, the twins, Castor and Pollux highlight the Gemini. UWF alumni can associate the pair with Jason and the Golden Fleece legend, for they were the first two Argonauts to sign up on his crew of adventurers. Jupiter now sits in the middle of Gemini, far brighter than any other object of the winter sky.

South of Gemini, Orion is the most familiar winter constellation, dominating the eastern sky at dusk. The reddish supergiant Betelguese marks his eastern shoulder, while blue-white supergiant Rigel stands opposite on his west knee. Just south of the belt, hanging like a sword downward, is M-42, the Great Nebula of Orion, an outstanding binocular and telescopic stellar nursery. It is part of a huge spiral arm gas cloud, with active star birth all over the place.

Last but certainly not least, in the east rise the hunterís two faithful companions, Canis major and minor. Procyon is the bright star in the little dog, and rises minutes before Sirius, the brightest star in the sky. Sirius dominates the SE sky by 7 PM, and as it rises, the turbulent winter air causes it to sparkle with shafts of spectral fire. Beautiful as the twinkling appears to the naked eye, for astronomers this means the image is blurry; only in space can we truly see "clearly now". At 8 light years distance, Sirius is the closest star we can easily see with the naked eye. Below Sirius in binoculars is another fine open cluster, M-41, a fitting dessert for New Yearís sky feast.

Read past issues of the Sky at Night