Zeta Scorpii

StarDate: July 29, 2009

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The celestial scorpion skitters low across the southwestern sky the next few weeks. In fact, it's so low that its tail barely clears the horizon.

The star that marks the junction between Scorpius's tail and the body doesn't look special at all. It's known as Zeta Scorpii. Binoculars reveal that it's really two stars, not one. They're not related, though. Zeta-2 is about 150 light-years away, while Zeta-1 is many times farther -- up to six thousand light-years. That means that while Zeta-1 looks puny, it's actually one of the most impressive stars in the galaxy.

Zeta-1 is a supergiant. It's about 60 times as massive as the Sun. Because of that great heft, it burns through the nuclear fuel in its core in a hurry. All of that energy heats its outer layers to tens of thousands of degrees. And the combination of its size and temperature makes it extremely bright: If you add up all of its energy -- the light we see, plus other forms of energy we can't see -- Zeta-1 is probably a million times brighter than the Sun.

That showiness carries a price, though: Zeta-1 Scorpii will live just a few million years, versus a few billion years for more sedate stars like the Sun. When it burns through all of its fuel, it'll explode as a supernova, briefly shining billions of times brighter than the Sun. Its core may be crushed to form a black hole -- a dark fate for one of the galaxy's brightest stars.

We'll have more about Scorpius tomorrow.

Script by Damond Benningfield, Copyright 2009

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