Skylights featured on Astronomy Picture of the Day

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


Photo of the Week. Faint Neptune, seen here last November 8, glides past the stars of northeastern Capricornus.

Astronomy news for the week starting Friday, December 3, 2010.

This is the dark-sky week of the new Moon, the phase passed early, on Sunday, December 5, after which it spends its time waxing in the crescent phase. With luck you might see the ultra-thin crescent in evening twilight the night of Monday the 6th, the view improving on subsequent nights. As it goes along its zodiacal path, the Moon invisibly passes Mercury (which is not presenting much of an apparition) on Tuesday the 7th.

Though formal winter and the shortest day of the year are yet a ways off, take heart, as because of the eccentricity of the Earth's orbit and the tilt of its axis, the earliest sunset is coming up on Tuesday the 7th, after which it will begin to get lighter in the evening.

The evening and morning hours are dominated by the two brightest of planets, Jupiter and Venus. Jupiter, now in direct easterly motion near the Aquarius-Pisces border, transits the meridian to the south about 6:30 PM, less than half an hour past the end of evening twilight, setting half an hour after midnight. But an hour and a half later, up comes Saturn, still well to the west of Virgo's Spica.

The real show, however, begins just after 3:30 AM, when Venus lofts itself up above the still-dark eastern horizon. Positively glowing, the amazing planet remains easily visible well into bright twilight. Hitting a morning milestone, it reaches greatest brilliancy the morning of Saturday the 4th, its subsequent fading not for some time noticeable to the eye. Seen as a crescent through the telescope, Venus is so bright that it is visible in full daylight and in a dark sky will cast eerie shadows on the ground.

Back in the evening, Uranus, still just over a couple degrees to the northeast of Jupiter, ceases retrograde motion on Monday the 6th, when it begins its normal easterly movement against the stars. Faster moving Jupiter will catch up with next January 2, when the two will be a mere 0.6 degree apart, about the angular diameter of the full Moon.

Jupiter provides a good guide to one of the fainter constellations of the Zodiac. Look just to the north of it to find the ragged circle of stars that makes the "Circlet" of Pisces, the celestial Fishes. The rest of the figure sprawls in a long line to the east until it meets up with another rough circle that makes the head of Cetus, the Whale or Sea Monster, after which it turns to the north. Just to the right of the Circlet, find the Y-shaped "Water Jar" of Aquarius.
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