16h47m14.52s, −01° 56′ 52.1″Messier 12
IX[1]
16h47m 14.18s[2]
–01° 56′ 54.7″[2]
16.44 ± 0.16 kly (5.04 ± 0.05 kpc)[3]
6.7[4]
Apparent dimensions (V)
16.0′
Physical characteristics
Mass
Radius
37.2 ly[NB 1]
Estimated age
Other designations
See also: Globular cluster, List of globular clusters
Messier 12orM 12 (also designated NGC 6218) is a globular cluster in the constellationofOphiuchus. It was discovered by the French astronomer Charles Messier on May 30, 1764, who described it as a "nebula without stars".[8] 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 8 in (20 cm) or greater.[9] In a 10 in (25 cm) scope, the granular core shows a diameter of 3′ (arcminutes) surrounded by a 10′ halo of stars.[8]
M12 is roughly 3°[9] northwest from the cluster M10 and 5.6° east southeast from star Lambda Ophiuchi. It is also located near the 6th magnitude 12 Ophiuchi.[10] The cluster is about 16,400 light-years (5,000 parsecs)[3] 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.[10] With a Shapley-Sawyer rating of IX,[1] 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.[11]
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.[12]
Stars
Outer space
See also
Portal
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