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Messier 21 |
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 | The open cluster M21, or NGC6531, in the constellation Sagittarius. This cluster shows a strong central concentration and a wide range of star brightnesses, despite its limited membership of probably fewer than 60 stars. Most likely quite young (for a star cluster, that means only a few million years), its distance is uncertain.
This cluster is just out of the field of view of the Trifid Nebula. It is fairly loose, without too many members. Again, it is somewhat difficult to tell exactly which stars are members, but there is a bright knot of six stars off to one side, and that's the biggest concentration. All told, there are probably about 20 members visible. Around the edges are bright stars in a pentagram or star shape. The bright knot is located at one of these points. |
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| You can find more information about this Messier object by visiting: SEDS - The Messier Catalog. |
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M21 NGC 6531 Other description: Open cluster rich. Constellation: Sagittarius Dreyer description: Cluster, westward rich in stars, little compressed, stars of magnitude 9 to 12; = M21. Magnitude: 5.9 RA: 18h 04m 52.1s Dec: -22°30'05" RA: 18h 04m 36.0s Dec: -22°30'00" (Epoch 2000) Azm: 22°31'52" Alt: -64°49'54" Rise: 20:27 Transit: 00:48 Set: 05:12 Size:13.0' |