Starry Night: Early December 2011

Posted Wednesday, November 30, 2011 in Features

Starry Night: Early December 2011

Geminids, a photo taken in 2010 by Wally Pacholka, courtesy National Geographic.

Early December: The Geminids return to the night sky

by Tristan Radtke

Around mid-December, the Geminid meteor shower produces a show of slow-moving, often yellow meteors which can span the entire sky and, although usually centered around Gemini, can also appear from just about anywhere in the night sky and be moving in just about any direction. This meteor shower produces these very different meteor paths due to its source – an asteroid debris field, rather than a comet – which is far slower moving and larger, in terms of its distribution when it strikes the atmosphere, but far less dense. This means while the shower will produce a small number of meteors per hour comparatively, the meteors themselves will be more interesting in appearance and with a longer lifespan as they strike the atmosphere at a very shallow angle, spreading across the night sky rather than plunging towards the Earth. Along with the Quadrantids, this shower is one of only two northern hemisphere periodic meteor showers that are produced by a non-comet astral body.

This year’s shower is expected to peak around Dec. 14, and although that will be a good night for viewing as it occurs around the darkest portion of the year, it will be hampered a bit this year by the moon, which will rise around 9:30 p.m. on Dec. 14, and will be in the process of waning from full to third-quarter phase at that point in the month. Nonetheless, with a wide distribution across the night sky and an anticipated peak of 120 to 160 meteors per hour, the avid sky watcher will likely be able to spot the shower, particularly in the early morning hours, from around 1 a.m. to about 4 a.m.

The Stars

Next door to the Greater and Lesser Dogs is another zodiacal constellation, Gemini, the Twins. The Twins represent Castor and Pollux. In mythology, Castor and Pollux were the sons of Leda, but while one of the twins' father was a mortal, the king of Sparta, the other's father was Zeus.  Castor, therefore, was mortal, while Pollux was immortal. When Castor was killed, Pollux asked Zeus to allow him to share his immortality with his brother, and thus they spent half their time on Mount Olympus and half in Hades, with the mortal dead. They became the two brightest stars of the Gemini constellation. In the constellation, Castor and Pollux (the stars) represent the heads of the twins, who cannot bear to be separated.

The Planets

• Mercury: Mercury begins the month of December lost in the glare of the setting sun. By Dec. 15, however, Mercury will be the morning star, rising at around 5:30 a.m.

• Venus: Venus is bright and easily visible on Dec. 1, setting around 5:45 p.m. By mid-month, Venus will set by 6:15 p.m.

• Mars: Mars starts out the last month of the year rising at around 11 p.m. On Dec. 15, Mars will rise at around 10:45 p.m.

• Jupiter: Jupiter will start the month of December setting around 3:15 a.m. By the middle of the month, it will set around 2 a.m.

• Saturn: Saturn will mirror Jupiter, rising at around 3:15 a.m. on Dec. 1 in Virgo, in line with the bright star Spica. By Dec. 15, Saturn and Spica will both continue to mirror Jupiter, rising around 2 a.m.

• Uranus: Uranus will set around 12:15 a.m. on Dec. 1, and by the middle of the month it will swap to set in the evening at around 11:15 p.m.

• Neptune: Neptune will be dim this month and hard to spot, but it will begin the month setting around 10 p.m. On Dec. 15, it will set around 9 p.m.

• Pluto: Pluto is extremely dim this month, with a magnitude of 14.15, but it may be visible with a telescope and the right light conditions on Dec. 1 in the hour after sunset, a bit higher above the horizon from Venus. By mid-month, it will likely be too close to the setting sun to be visible, itself setting around 5 p.m.

The Moon

The moon begins December waxing, and reaches its first quarter on Dec. 2. After becoming full on Dec. 10, it will begin waning, and reaches third quarter by Dec. 18.

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