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August 8, 2011

One of the favorite constellations of summer soars high across the sky this month: Cygnus, the swan. It stretches across the east and northeast at nightfall. Its brightest stars form a pattern that really does look like a graceful swan, soaring through the misty glow of the Milky Way.

Its brightest star is Deneb, which marks the swan's tail. It's one of the most impressive stars in the galaxy -- it's far larger, heavier, and brighter than the Sun. More about Deneb tomorrow.

But no less impressive is the star that marks the center of the swan's outline, where its outstretched wings meet its long body. It's known as Sadr, a name that means "the hen's breast."

Like Deneb, it's a supergiant. It's more than 10 times as massive as the Sun, hundreds of times wider, and about 65,000 times brighter. That makes it easy to pick out even though it's around 1500 light-years away.

Supergiants are the biggest and most massive of all the stars. They "burn" through their hydrogen fuel in a hurry, so they live short lives -- in the millions of years, versus billions of years for stars like the Sun.

And when they die, they go out with a titanic explosion known as a supernova. And if the estimates of Sadr's distance and mass are correct, that's exactly the fate that awaits it, sometime in the next few million years.

So look for Cygnus flying high across the sky tonight, with its brightest star, Deneb, at the northeastern point of the wide Summer Triangle.


Script by Damond Benningfield, Copyright 2011


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