Post by glactus on Feb 23, 2009 1:13:03 GMT
The Pleiades (Seven Sisters)
In astronomy, the Pleiades (M15) are an open star cluster in the constellation of Taurus. It is among the nearest star clusters at a distance of only 440 light years, and is the cluster most obvious to the naked eye in the night sky.
The Pleiades are a prominent sight in winter in the Northern Hemisphere and in summer south of the equator.
Charles Messier measured the position of the cluster and included it as M45 in his catalogue of comet-like objects, published in 1771.
The cluster is dominated by hot blue stars that have formed within the last 100 million years. Dust that forms a faint reflection nebulosity around the brightest stars was thought at first to be left over from the formation of the cluster but is now known to be an unrelated dust cloud in the interstellar medium that the stars are currently passing through.
Astronomers estimate that the cluster will survive for about another 250 million years, after which it will disperse due to gravitational interactions with its galactic neighborhood.
Credits: This is a NASA/Hubble image
