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Moon and Leo

December 24, 2010

The strong heart of a king follows the Moon across the sky tonight: the star Regulus. Its name means "the little king." And it's the brightest star of Leo, the lion -- the king of the beasts. It's to the lower left of the Moon as they rise in mid-evening.

If you look closely, though, you'll see that another of Leo's stars is even closer to the Moon. It's less than a tenth as bright as Regulus, so most of the time, you might not even notice it. But its proximity to the Moon will make it a little more obvious.

The star is known as Omicron Leo, and as Subra. The latter name means "the lion's mane." It's a bit misplaced, since the star is actually where the lion's foot should be. The name originally applied to two stars that do represent the mane, which is to the left of Regulus.

Omicron Leo is about 135 light-years away. It consists of two stars that orbit each other once every two weeks. They're only about half as far from each other as Mercury is from the Sun.

As seen from Earth, the stars blur into a single point of light, so it's tough to pin down the characteristics of each star. But we do know that both stars are larger, brighter, and more massive than the Sun. Because of their extra heft, they'll burn through their nuclear fuel more quickly than the Sun, too, so they'll expire billions of years sooner.

For now, though, watch Omicron Leo as it passes within a whisker's-width of the Moon this evening.


Script by Damond Benningfield, Copyright 2010


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