The Crane

StarDate: December 4, 2009

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An elegant crane is standing tall right now: the constellation Grus. From south of about Kansas City, it stands straight up from the southern horizon in early evening.

Grus is fairly new as constellations go. Its stars originally formed part of Piscis Austrinus, the southern fish. But in the late 1500s, after they journeyed to the southern hemisphere, a pair of Dutch navigators laid out 12 new constellations -- including Grus.

Its brightest star, Al Nair, is one of the crane's feet. The star is a good bit bigger, hotter, and brighter than the Sun. And it's just coming to the end of its time on the main sequence -- the time when a star burns through the hydrogen in its core to make helium. When the hydrogen is gone, it starts burning the helium to make even heavier elements. As it does so, it gets bigger and brighter -- and that's what's happening to Al Nair.

That's already happened to the crane's second-brightest star, Beta Grus. If it took the Sun's place in our own solar system, it would extend past the orbit of Venus, the second planet out. It's near the point where it no longer produces energy in its core. When it reaches that point, its outer layers will blow off into space, leaving only its hot but tiny core -- a white dwarf.

Look for the crane striding atop the southern horizon an hour or two after sunset. Al Nair and Beta Grus -- the feet -- are side by side, with a streamer of fainter stars craning above them.

Script by Damond Benningfield, Copyright 2009

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