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Moon, Mars, and Gemini

February 25, 2010

The Moon and some bright companions form a figure that looks a little like a golf club tonight. They're high in the east at nightfall, and soar high overhead later on.

The Moon and the planet Mars form the head of the club. Mars is a little to the left or upper left of the Moon, and looks like a brilliant orange star.

Mars remains quite bright because it's still fairly close to Earth. It passed closest to us just a few weeks ago, and is slowly pulling away. As it does so, it'll begin to fade. Three months from now, the planet will shine just one-fifth as bright as it is tonight. And by mid-summer, it'll be just one-tenth as bright.

Up above Mars and the Moon, the brightest stars of Gemini form the club's grip. Pollux is closer to Mars, with Castor above it.

In mythology, Castor and Pollux are twins. Yet the stars that represent their heads definitely aren't twins. To the eye alone, Pollux shines about half again as bright as Castor, and it has a much redder color.

Telescopes and sensitive instruments reveal even greater differences. Pollux is a giant -- an old star that's bloated to gigantic proportions. It'll soon cast off its outer layers, leaving behind only its hot, dense core. Castor, on the other hand, is a system of at least six stars, which are bound together as three sets of twins.

Look for Castor and Pollux leading the Moon and Mars across the sky tonight. They set in the wee hours of the morning.

Script by Damond Benningfield, Copyright 2009

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