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August 7, 2010

The faint band of the Milky Way runs across the heavens on summer nights. Several bright constellations are embedded within this band of light, including Cygnus, the swan, and Aquila, the eagle. They're well up in the east by nightfall.

Several faint constellations fill the gaps between the bright ones, including one between Cygnus and Aquila: Vulpecula, the fox.

Its brightest star is Alpha Vulpeculae. It's only fourth magnitude, so you need pretty dark skies to see it.

The star is a red giant -- a star that's much larger and cooler than the Sun, and that's nearing the end of its life.

When a red giant dies, it casts its outer atmosphere into space. That exposes its hot, dense core, whose radiation makes the expelled gas glow like the inside of a fluorescent bulb. As a result, telescopes reveal a bubble of glowing gas called a planetary nebula.

And in fact, Vulpecula's best-known resident isn't a star at all, but a planetary nebula known as the Dumbbell Nebula. If this nebula surrounded the Sun, it would stretch a quarter of the way to the stars of Alpha Centauri, our nearest stellar neighbors.

The Dumbbell contains a lot of carbon and nitrogen, two life-giving elements that were forged in the heart of the star that gave birth to the nebula. And when Alpha Vulpeculae dies, it, too, will enrich the galaxy with nitrogen and carbon -- elements that may help sustain life on planets that are yet to be born.

Script by Ken Croswell, Copyright 2010

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