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Alpha Persei Cluster

October 9, 2011

The constellation Perseus rises in the northeast around sunset this month. Its brightest star, Alpha Persei, is a member of a large cluster of stars. Several other members of the cluster are also visible to the unaided eye, with many more showing up in binoculars.

The cluster is more than just a pretty sight, though. It may mark “ground zero” for a cataclysm that wracked our part of the galaxy 50 million years ago.

The Alpha Persei cluster is 600 light-years from Earth. That puts it near the center of an enormous ring of bright stars known as Gould’s Belt, which encircles our position in the galaxy. At its widest, the belt is more than 2,000 light-years in diameter. It contains many of the brilliant stars in Orion, Scorpius, and many other constellations. Yet no one knows what caused it.

But astronomers do know that Gould’s Belt is expanding. By tracing that expansion, they’ve deduced that it originated around the same time as the Alpha Persei cluster. Although this might be just a coincidence, it suggests that the two are related. Perhaps a giant gas cloud hit the Milky Way and caused the formation of the Alpha Persei cluster. Then supernova explosions in the cluster pushed away gas, triggering the birth of more stars in an expanding ring that we now see as Gould’s Belt.

Other star clusters are more spectacular. But the Alpha Persei cluster may hold an important clue to one of the biggest mysteries surrounding our part of the galaxy.


Script by Ken Croswell, Copyright 2011


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