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Orion's Belt

January 13, 2011

Being a member of a popular group can make you famous -- just not as yourself. Consider, for example, the three stars at the center of Orion, the hunter. They're some of the biggest, brightest stars in the galaxy. Yet almost no one pays attention to them as individuals. Instead, we think of them as a group: Orion's Belt.

Orion is in full view in the east by nightfall. The belt points straight up from the horizon, with Orion's other bright stars arrayed to its left and right.

From top to bottom, the stars of the belt are Mintaka, Alnilam, and Alnitak. The names are from ancient Arabic. Mintaka and Alnitak refer to the "Belt of the Great One" -- a giant figure whose origin is unknown. Alnilam refers to an alternate name for the belt -- the "string of pearls."

There's no doubt that these three stars are among the most impressive jewels in the Milky Way galaxy.

Mintaka and Alnitak are binaries. Each consists of two supergiant stars -- stars that are many times more massive than the Sun, and tens of thousands of times brighter.

They're also much younger than the Sun -- only a few million years old, compared to a few billion years for the Sun. Even so, they're much closer to the ends of their lives than the Sun is. They're burning through their nuclear fuel in a hurry, and will soon expire -- perhaps in a spectacular fashion.

That's certainly the case for Alnilam, which is the leader of this titanic trio. More about that tomorrow.

Script by Damond Benningfield, Copyright 2010

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