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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9 -- Full List Restored!

Comet Halley

Photo of the Week. Now it's Halley's Comet as it appeared in early March of 1986. See full resolution. University of Illinois and San Diego State University, courtesy of Ron Angione.

Astronomy news for the two weeks starting Friday, December 6 2013.

The next Skylights will appear Friday, December 20, 2013.

We begin the week with the Moon in its waxing crescent phase as it heads towards first quarter, which is passed on Monday, December 9, shortly before it rises in North America. As it rounds the Earth it then moves into the waxing gibbous, which ends with full Moon on Tuesday the 17th. During the remainder of the fortnight, the Moon fades in the waning gibbous phase. The evening of Friday the 6th, look for the waxing crescent well up and a bit to the left of Venus. The night of Saturday the 14th, the rising Moon will shine to the right of the Pleiades, while the next evening finds it smack in the Hyades of Taurus, with Aldebaran below it. The full Moon then visits Jupiter, seen rising well to the west of it the night of Tuesday the 17th, then just to the south the following night. The Moon passes apogee, farthest from Earth, on Thursday the 19th. Of more interest, because of the Earth's orbital eccentricity and axial tilt, we see the earliest sunset of the year on Saturday the 7th in spite of Winter Solstice passage not taking place until Friday the 21st.

Venus and Jupiter dominate the early evening, though Venus is starting to slip away. Reaching its greatest brilliance on Friday the 6th, the planet does not set in the southwest until an hour after the sky gets fully dark. By that time, Jupiter is well up in the northeast and quite unmistakable near the star Delta Geminorum (Wasat) more or less south of Castor and Pollux. Jupiter then crosses the meridian to the south one to two hours after midnight, getting earlier as the fortnight proceeds. By that time, Mars is up in the east as it plods easterly against the stars of western Virgo, crossing the celestial equator into the southern hemisphere on Monday the 16th. Saturn then rises in the southeast in Libra shortly before dawn, giving us three planets to admire.

The highlight of the our two-week period (and one of the reasons for it) is the Geminid meteor shower, which runs roughly between December 11 and 15 and peaks the morning of Saturday the 14th, when in a dark sky you might see more than 100 meteors an hour that seem to come out of the constellation Gemini. Unfortunately, the bright gibbous Moon will get in the way. The Geminids are strange in that they are the debris of the "asteroid" Phaeton, which behaves more like a comet that takes but 1.4 years to orbit the Sun. Clearly the minor bodies of the Solar System are more complex than was once thought.

By mid evening, the autumn stars, featuring those of the Andromeda myth (including Cassiopeia, Pegasus, Perseus, and so on), are shining near the meridian, while those of Summer (Lyra, Cygnus) have dropped far into the northwest. We await then the constellations of true winter, which center on great Orion, with Taurus and Gemini above him, Lepus (the Hare) below, and Sirius, of Canis Major, his larger Hunting Dog and the brightest star of the sky, to the southeast.
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