Orion's Belt

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• 7 of 1969
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Orion, the hunter, charges across the evening sky right now. He stands high in the south in mid to late evening. Two bright stars at the top of the constellation mark his shoulders, while two more bright stars closer to the horizon mark his knee and foot. Near the center of the large rectangle formed by these stars is Orion's Belt, a short line of three bright stars.

In Greek mythology, Orion was a great hunter, so it's not surprising that early stargazers saw the stars as a thick, heavy belt holding a sword.

The westernmost star in Orion's Belt -- the star at the right end of the belt -- is Mintaka. It sits almost directly astride the celestial equator -- the projection of Earth's equator on the sky, dividing northern from southern skies.

Mintaka is really a multiple-star system -- three stars bound to each other by their gravity. It consists of an intensely bright blue star; a second star that's too faint for us to see, but that reveals itself by passing between the blue star and Earth once every six days; and a third star, which we can see, that's a greater distance from the blue star.

The center star in Orion's Belt is Alnilam. Its name comes from an Arabic word that means "string of pearls." The Belt's eastern star is Alnitak -- "the girdle" -- which is a binary system.

All of the bright stars of Orion's Belt are about 1500 light-years from Earth. And all are on display in the evening sky.

More about Orion tomorrow.

Script by Damond Benningfield, Copyright 2003, 2007

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