There's a bit of a logjam in the western sky tonight. The Moon, Mars, and the twin stars of Gemini are packed together like paparazzi chasing a naughty starlet.
As night falls, the Moon and the twins -- the stars Pollux and Castor -- form an equally spaced line high in the west. The stars are to the right of the Moon as you face west. Mars looks like a bright orange star below them.
Although Pollux and Castor represent twins, the stars themselves are quite different.
Brighter Pollux is a red giant -- a star that's nearing the end of its life. It's puffed up like a balloon, cooling its outer layers and giving the star an orange tint. Over time, those outer layers will drift away into space, leaving behind the star's hot, dense core. It's the same fate that awaits the Sun in several billion years.
Castor, on the other hand, is a big stellar family -- six stars in all. Four of them are close together, while two more are split a good ways off. The brightest of the bunch is a vigorous young star with a surface that glows white-hot. The stars of Castor are about half-again as far as Pollux is, so there's no connection between Gemini's twins -- they just line up in the same direction in space.
And tonight, the Moon and Mars line up that way, too. They're high in the west at nightfall, and descend the northwestern sky later on. Mars sets around 2 or 3 a.m., with the rest of the group following about an hour later.
Script by Damond Benningfield, Copyright 2008
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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