Messier 12, NGC 6218

Messier 12 (NGC 6218) is a globular cluster in the constellation Ophiuchus, discovered by Charles Messier in 1764. William Herschel was the first to resolve it into stars, in 1783.

M 12 is easily found, 8.5° east of Delta Ophiuchi, and 3° west of the globular cluster Messier 10. It is nearly a twin of its apparent neighbor; M 12 is only slightly larger (16') and a little fainter (magnitude 6.7) than M 10. Messier 12 is a loosely-packed globular cluster and was once thought to be a tightly concentrated open cluster; its brightest stars are of 12th magnitude.

Messier 12 is about 16,000 light-years distant, and has a spatial diameter of 75 light-years. A recent study has concluded that M 12 has lost over a million stars, stripped from the cluster by the gravitational influence of the Milky Way.