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Messier 72(Globular Cluster)
Ke'er Lin

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The cluster M72 is a Globular Cluster, which is in Aquarius. It was discovered in 1780 by Pierre Mechain. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers.  However, due to its large distance, about 53,000 light years away, M75 is one of the apparently smaller and fainter globular clusters in Messier’s catalog. M72 is approaching us quite rapidly, at 255 km/sec. According to the Deep Sky Field Guide to Uranometria 2000.0, the brightest star in M72 is about 14.2 mag, so it is fairly faint.  

We can see that thousands of stars are gathered in the center. There are some bright stars spread all around, actually, which do not belong to M72. But by observing its structure, it perfectly shows the properties of a Globular Cluster. By using small angle formula, we can figure out the linear size which is about 100 LY.

J2000 coordinates RA: 20h 53m 30.0s Dec: -12°32'00"
Filters Clear
Exposure times 4x300s
Dates 10/27/2010

 

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