Messier 12
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Messier 12 or M 12 (also designated NGC 6218) is a globular cluster in the constellation of Ophiuchus. It was discovered by the French astronomer Charles Messier on May 30, 1764, who described it as a "nebula without stars".[1] In dark conditions this cluster can be faintly seen with a pair of binoculars. Resolving the stellar components requires a telescope with an aperture of Script error: No such module "convert". or greater.[2] In a Script error: No such module "convert". scope, the granular core shows a diameter of 3Template:Prime (arcminutes) surrounded by a 10Template:Prime halo of stars.[1]
M12 is roughly 3°[2] northwest from the cluster M10 and 5.6° east southeast from star Lambda Ophiuchi. It is also located near the 6th magnitude 12 Ophiuchi.[3] The cluster is about Script error: No such module "convert".[4] from Earth and has a spatial diameter of about 75 light-years. The brightest stars of M12 are of 12th magnitude. M10 and M12 are only a few thousand light-years away from each other and each cluster would appear at about magnitude 4.5 from the other.[3] With a Shapley-Sawyer rating of IX,[5] it is rather loosely packed for a globular and was once thought to be a tightly concentrated open cluster. Thirteen variable stars have been recorded in this cluster. M12 is approaching us at a velocity of 16 km/s.[6]
A study published in 2006 concluded that this cluster has an unusually low number of low-mass stars. The authors surmise that they were stripped from the cluster by passage through the relatively matter-rich plane of the Milky Way.[7]
See also
Notes
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References
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External links
- Messier 12, SEDS Messier pages
- Messier 12, Galactic Globular Clusters Database page
- 'Stolen' stars article at Universe Today
- Messier 12, Amateur astrophotographer (hgg) with a Celestron 9.25"
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