M12 - Globular Cluster in Ophiuchus
Discovered by Charles Messier in 1764.
M12 is nearly a twin of its apparent neighbor, M10, and is only slightly larger and an idea fainter. Nevertheless, it was once believed to be an intermediate type between globular and dense open clusters (like M11), as it is not very concentrated. It is notably much less concentrated toward the center than M10. At its distance of about 16,000 light years, the apparent diameter of M12 of 16.0 arc minutes corresponds to about 75 light years. This stellar swarm is approaching us at 16 km/sec.M12 is one of Charles Messier's original discoveries, found on May 30, 1764. Like many other globular clusters, Messier described it as "Nebula without stars", as did Bode 10 years later; a consequence of the modest resolving power of their instruments. William Herschel was the first to resolve it into stars in 1783.