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orange sunrise

Photo of the Week. Orange sunrise.

Astronomy news for the week starting Friday, December 19, 2008.

Best to all and wishes for a fine holiday season.

The Moon starts the celebration by being in its third quarter on Friday, December 19. The past couple weeks have been bracketed by lunar phases of the moment. Now we start to stretch things out, as the rest of the week is spent with the Moon in its waning crescent phase, new Moon not passed until Saturday the 27th (the interval between exact phases being about 7 1/3 days). Your last view of the crescent could be had in cold eastern twilight the morning of Thursday the 25th, Christmas morning, should you want to venture out, the Moon just having passed Antares in Scorpius.

On the other side of the day and sky, the early evening remains studded with Jupiter and Venus. Pulling ever farther apart since their dramatic conjunction, Jupiter sets ever earlier (just after the end of twilight), while Venus sets ever later, not until after 8 PM. The planetless gap (ignoring the dim outer ones) is no longer as large, with Saturn now rising in the late evening hours, around 11 PM. In far southeastern Leo, well to the southeast of Regulus, Saturn is barely moving easterly as it approaches the boundary with Virgo. Returning to the outer planets, Pluto invisibly passes conjunction with the Sun on Monday the 22nd, Pluto some six degrees to the north of the Sun thanks to its large orbital tilt.

Now it's back to Earth, as the Sun passes the Winter Solstice in Sagittarius at 6:04 AM CST (7:04 EST, 5:04 MST, 4:04 PST, subtract another hour each for Alaska and Hawaii) on Sunday the 21st, marking the beginning of northern winter and the northern hemisphere's shortest day (and for astronomers, the longest night). At that time, the Sun will be as far south as it gets (23.4 degrees south of the celestial equator), will pass overhead at the Tropic of Capricorn, and, except in the Arctic and Antarctic, will rise and set as far to the south of east and west as possible.

Just before Venus sets, Sirius -- the sky's brightest star -- rises, and the winter constellations begin to come into full glory. Now is the time to admire great Orion as he climbs the eastern sky, the Hunter instantly recognizable by his three-star Belt. But don't forget those of autumn. In mid- evening, Pegasus has moved off to the west, while Andromeda still lies close to overhead. If the sky is dark, between the Great Square of Pegasus and Orion you might locate the rounded dim head of the villain of the Andromeda myth, Cetus, the Whale or Sea Monster.
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