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August 28, 2012

As you gaze upon the stars in the night sky, it’s tempting to think of them as fixed neighbors — like rows of houses scattered through the galactic suburbs. But that’s not the case at all. The stars all came from somewhere else, and they’re moving at different speeds around us, so the layout of the neighborhood changes.

It’s hard to tell just where each star came from, though. Some were born in the broad, thin disk of the Milky Way galaxy, just as the Sun was. Others were born just outside this disk. And still others were born in other galaxies that were swallowed by the Milky Way.

One star whose origins have been a bit of a puzzle is Arcturus, the brightest star of Bootes. The bright star is well up in the west at nightfall, and shines yellow-orange.

Arcturus is nearing the end of its life, so it’s puffed up to giant proportions. Although it’s about as massive as the Sun, it’s about 25 times wider, which also makes it burn brighter.

Some studies have suggested that Arcturus came from another galaxy. But a study released last year came to a different conclusion. The study’s authors plotted the star’s composition, motion, and other characteristics. From that, they concluded there’s a 94 percent chance Arcturus was born in the puffy outer regions of the Milky Way, known as the “thick disk.” Over the eons, it worked its way into our region of the galaxy. As time continues to pass, though, so will Arcturus — away from Earth and out of sight.

Script by Damond Benningfield, Copyright 2012


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