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.

2005 April 6
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

The M7 Open Star Cluster in Scorpius
Credit & Copyright: Allan Cook & Adam Block, NOAO, AURA, NSF

Explanation: M7 is one of the most prominent open clusters of stars on the sky. The cluster, dominated by bright blue stars, can be seen with the naked eye in a dark sky in the tail of the constellation of Scorpius. M7 contains about 100 stars in total, is about 200 million years old, spans 25 light-years across, and lies about 1000 light-years away. This color picture was taken recently at the Kitt Peak National Observatory in Arizona, USA as part of the Advanced Observers Program. The M7 star cluster has been known since ancient times, being noted by Ptolemy in the year 130 AD. Also visible is a dark dust cloud near the bottom of the frame, and literally millions of unrelated stars towards the Galactic center.

Tomorrow's picture: sunbite


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