Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2007 June 9
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

Globular Star Cluster M3
Credit & Copyright: Karel Teuwen

Explanation: This immense ball of half a million stars older than the Sun lies over 30,000 light-years away. Cataloged as M3 (and NGC 5272), it is one of about 150 globular star clusters that roam the halo of our Milky Way Galaxy. Even in this impressively sharp image, individual stars are difficult to distinguished in the densely packed core, but colors are apparent for the bright stars on the cluster's outskirts. M3's many cool "red" giant stars take on a yellowish cast, while hotter giants and pulsating variable stars look light blue. A closer look at the deep telescopic view also reveals a host of background galaxies. Itself about 200 light-years across, the giant star cluster is a relatively bright, easy target for binoculars in the northern constellation Canes Venatici, The Hunting Dogs, and not far from Arcturus.

Tomorrow's picture: earth spot

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