Venus, moon and bright star to dazzle Thursday

Image: Sky map of Venus, crescent moon and bright star Spica
This sky map shows how the bright planet Venus, crescent moon and bright star Spica will appear in the predawn sky on Dec. 2, 2010 at 6 a.m. ET from the northeastern U.S. The triple sky show promises to dazzle skywatchers with clear skies. Starry Night
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If you've been up before sunrise during this past week and gazed at the east-southeast sky, you may have noticed the return of the brightest of all planets, Venus, glimmering like a sequined showgirl with a silvery-white light. But if not, you may want to catch Thursday's triple sky show of Venus, the moon and a bright morning star.

The view, weather permitting, should be worth setting your alarm clock for on Dec. 2. At about 6 a.m. ET, there will be a beautiful configuration involving Venus, a slender crescent moon and the bluish first magnitude star, Spica in the constellation Virgo. 

This sky map shows where to look to see Venus, the moon and Spica Thursday morning.

On that morning, if you face southeast, youll readily see the moon, flanked by a brilliant Venus to its upper left, while Spica shining only about 1/250 as bright as Venus hovers almost directly above the moon.

The trio will form a very striking, albeit wide, triangle that will almost certainly catch the eyes of early morning commuters en route to work and school. [ Gallery: Venus photos from around the world ]

Brilliant Venus
From late February into early October, Venus was an evening object, appearing low in the western sky soon after sunset.  Now, it will keep early risers company through the first half of 2011.

Venus passed inferior conjunction (appearing to pass between the sun and Earth) back in late October.

During the first days of November Venus was invisible, mired deep in the brilliant glare of the sun. But around Nov. 4, it started making itself evident in the morning sky, appearing very low to the east-southeast horizon about 40 minutes before sunrise.

Rising about six minutes earlier each day, Venus very quickly became a prominent morning object, climbing to glory in the southeast before dawn. By Nov. 11 the brilliant planet was rising about 90 minutes before the sun, and now it is rising more than three hours before sunrise.

As exceptional December
Venus is always bright, but during December the planet's brilliance and altitude will be exceptional.

During the winter holidays, the planet will shine like a modern-day "Christmas star in the east" before sunrise. Venus appears brightest Dec. 4.

If there's snow on the ground and you're in a dark, secluded location, check for faint shadows made by Venus' light. On clear mornings skywatchers should have little trouble following Venus right through the moment of sunrise. 

By the end of December, this lamp-like "Morning Star" will be rising during the dead of night, nearly four hours before the sun.

In January, Venus will continue to dominate the southeastern dawn sky. The ruddy first magnitude star Antares twinkles much fainter and well below it around midmonth.

Venus rises within a half-hour of 4 a.m. (your local time) all winter and spring as seen from mid-northern latitudes.

Incredible shrinking Venus
Between now and early next summer, repeated observations of Venus with a small telescope will show the complete range of its phases and disk sizes. 

The planet is currently displaying its distinctly large and narrow crescent shape, which should be easily discernable even in steadily, held 7-power binoculars.

Venus will arrive at its greatest western elongation or westernmost point from the sun on Jan. 8, 2011, and in a telescope its disk achieves what astronomers call dichotomy the appearance of being exactly half-illuminated a few days later.

For the rest of the winter and on into the spring, Venus will appear to get progressively smaller in angular size as it recedes from Earth while gradually becoming more and more illuminated by the sun.

By the end of June, it will be rising less than an hour before the sun and even in large telescopes it will appear only as a tiny, featureless, albeit brilliant disk. Shortly thereafter, it will disappear into the solar glare, passing behind the sun (superior conjunction) on Aug. 16 finally emerging back in the western dusk during next November, and especially December, of 2011.

New Year's Eve encore
Finally, if the weather is cloudy or unsettled the morning of Dec. 2, there is some consolation in knowing that Venus and the moon will perform an encore later this month.

Venus will appear with  a slender crescent for the second time in December, and the moon will once again form on the morning of Dec. 31, New Year's Eve.

On that day, Venus will hover well above and to the left of the moon to help ring in 2011.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.