Messier 12

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". 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. In a Template:Convert scope, the granular core shows a diameter of 3Template:Prime (arcminutes) surrounded by a 10Template:Prime halo of stars.

M12 is roughly 3° northwest from the cluster M10 and 5.6° east southeast from star Lambda Ophiuchi. It is also located near the 6th magnitude 12 Ophiuchi. The cluster is about Template:Convert 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. With a Shapley-Sawyer rating of IX, 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.

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.

• Messier 12 core by HST
  Messier 12 core by HST
• The Central Part of Messier 12. Credit: ESO
  The Central Part of Messier 12. Credit: ESO
• Map showing the location of M12
  Map showing the location of M12

See also

• List of Messier objects

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"
• Template:WikiSky