Messier 12
Template:Short description Template:Infobox globular cluster
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".<ref name=thompson_thompson2007/> 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 Template:Convert or greater.<ref name=monks2010/> In a Template:Convert scope, the granular core shows a diameter of 3Template:Prime (arcminutes) surrounded by a 10Template:Prime halo of stars.<ref name=thompson_thompson2007/>
M12 is roughly 3°<ref name=monks2010/> northwest from the cluster M10 and 5.6° east southeast from star Lambda Ophiuchi. It is also located near the 6th magnitude 12 Ophiuchi.<ref name=OMeara1998 /> The cluster is about Template:Convert<ref name=Gontcharov/> 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.<ref name=OMeara1998 /> With a Shapley-Sawyer rating of IX,<ref name=hcob849_11/> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
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.<ref name=eso2006/>
- M12 Hubble.jpg
Messier 12 core by HST
- ESO-Messier 12-Phot-04a-06.jpg
The Central Part of Messier 12. Credit: ESO
- M12map.png
Map showing the location of M12
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External linksEdit
- 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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