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The Night Sky of December

Dr. Wayne Wooten
Professor of Astronomy

For December 2013, the Moon will be new on December 3. The first two weeks find the moon waxing in the evening sky. The waxing crescent moon passes 7.5 degrees north of Venus on December 5th. The moon is first quarter on December 9th, and will interfere with the peak of the Geminid Meteor Shower on December 14th. The Full Moon, the Long Night Moon, is on December 17th. The winter solstice occurs at 11:11 AM CST on December 21st, and winter begins on the shortest day of the year. The waning gibbous moon passes five degrees south of Jupiter in the evening of December 19th. The last quarter moon rises at midnight on Christmas Day and passes 4 degrees south of reddish Mars. The waning crescent passes a degree south of Saturn in the dawn on December 29th.

Venus reaches its greatest brilliancy on December 10th, reaching magnitude -4.7, and easily visible in broad daylight if you know where to look. If you look above the crescent moon on December 5th about 4-5 PM on December 5th, Venus should be easy to spot. She is 30% sunlit crescent on December 1st, but she is overtaking Earth and passing between us and the Sun in early January 2014. At yearís end, she is a huge slender crescent, only 4% sunlit and neat to observe even in binoculars, as the phase changes by the day.

Mars is still far from earth and faint in the morning sky; the earth will overtake it in 2014, with a close opposition making Mars much brighter next Spring.

Jupiter dominates the evening sky for the next five months, brighter than any other planet now and imbeddedamong the stars of Gemini. Jupiter reaches opposition in January 2014. 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 Libra, and the famed rings are now open about 14 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.

As of this writing, the big question will be how bright Comet ISON will appear after its close perihelion passage of the Sun on Thanksgiving Day. I saw it with binoculars on November 9th in the dawn sky, and hope it brightens to naked eye visibility by mid November. I will be cautious in my finder chart for December morning skies, which show the comet climbing higher in the NE dawn sky, but fading as it pulls away from the Sun. It will hopefully be visible in binoculars throughout the month of December, but not the hoped for "Comet of the Century". But if it does split and spew out a lot of gas and dust on Thanksgiving Day, it may be indeed worth setting the alarm clock for 5 AM and getting up to see an impressive tail.

Stay tuned to the NASA website for a gallery of comet images and daily finder charts and updates on the cometís close passage by the sun as imaged with NASAís SOHO spacecraftís view of the comet in the Sunís corona near Thanksgiving. If the comet does brighten to put on a fine display, I will make every effort to let the local media know. Plan to observe it from a site with a clear SE horizon, since the comet will be brightest when still close to the Sun in the dawn on the first few mornings in December. If it does become spectacular, any digital camera, mounted on a tripod, and set for "nightshot" mode, may capture fine photos of this visitor from the distant Ort Cloud.

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. 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. Aldeberan is not a member, but about twice as close as the Hyades; distances in astronomy can be deceiving. Jupiter dominates the constellation Taurus this year, and now is retrograding just east of the Hyades, as Scottís photo shows.

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 starbirth 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.

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