This is a good evening to get acquainted with the the twins of Gemini, because the crescent Moon is passing through the middle of the constellation.
Gemini's brightest stars stand above the Moon -- Pollux to the left, and Castor to the right. They represent the heads of the twins.
Some of the constellation's other stars are closer to the Moon. They don't look as bright, but they're impressive in their own right.
Epsilon Geminorum is just to the right of the Moon, with Zeta Geminorum farther to the left. Both of these stars are supergiants -- stars that are far larger, heavier, and brighter than the Sun. They're far younger than the Sun, too. And because of their great mass, they'll never come near the Sun's current age of four and a half billion years -- they'll burn out billions of years before that.
Down to the lower left of the Moon is Gamma Geminorum, the constellations third-brightest star. It's a mere giant, so it's a lot more impressive than the Sun, but not nearly as impressive as a supergiant.
Gamma Geminorum has a companion star that's almost identical to the Sun. Its stretched-out orbit carries it from about the same distance between Earth and the Sun, to almost 20 times that distance. So as seen from the Sun-like star, Gamma Geminorum would grow noticeably brighter and fainter -- sometimes filling the sky like a giant heat lamp, and other times seeming cool and remote -- one of the impressive highlights of Gemini.
Script by Damond Benningfield, Copyright 2009
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