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Photo of the Week. Autumn sunset.

Astronomy news for the week starting Friday, December 21, 2007.

Wishes for the best of Holidays to all.

It's a busy week! The Moon starts us off in its waxing gibbous phase as it heads towards full the night of Sunday, December 23rd, Christmas Eve-Eve, thereafter reversing its phases and waning in the gibbous. Two days before full, the waxing gibbous passes through perigee, where it is closest to the Earth. The evening of Saturday the 22nd finds it in northeastern Taurus to the south of Auriga. The following night (Sunday the 23rd), the Moon takes on Mars, passing just barely north of it (the planet occulted as seen from Alaska and western Canada). Christmas Eve then finds the waning lunar disk smack in central Gemini. Finally, the night of Thursday the 27th, look for the Moon just south of Regulus in Leo to west of Saturn.

Two major events vie for attention. First, Mars passes its long- awaited opposition to the Sun the night of Monday the 24th, Christmas Eve, when it will rise at sunset, set at sunrise, and cross the meridian high to the south at local midnight, giving the red planet its best visibility. The planet is now also in its fastest retrograde (westerly) motion. The Earth then begins to pull away from Mars, but the difference in position is so slow that Mars will be nicely visible in the evening well into the summer of 2008. Countering the event, Jupiter, nearly opposite Mars, passes conjunction with the Sun the night of Saturday the 22nd. Becoming a morning object, Jupiter will become visible in dawn toward the end of January.

The other major event is the start of astronomical winter the night of Friday the 21st, the Sun passing the winter solstice in Sagittarius at 12:08 AM Central Time (1:08 AM EST, 11:08 PM PST, 10:08 PM PST). Winter thus actually begins the morning of Saturday the 22nd in eastern North America, the night of Friday the 21st in the western states and provinces. At that moment, the Earth's axis will be tilted away from the Sun, the Sun rises as far southeast and sets as far southwest as possible, the days are shortest, nights longest, and the Sun is as high at the south pole as it is ever going to get. From here on, the Sun will begin once again to climb the sky toward the equator, even as the days -- for awhile -- become still colder.

This is a good time to try to find one of the sky's larger critters, Cetus, the sea monster (or more benignly, the Whale). Look in early evening to the south of Aries and just to the north of the celestial equator for the faint ragged circle that makes its head, the body falling to the southwest, ending in bright Deneb Kaitos. In the middle is the fabulous variable star, Mira.
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