M107

M107 is a small, loose globular cluster in Ophiuchus, about 20,900 light-years from Earth. It is one of the more open and diffuse globular clusters in the Messier catalog, with a concentration class X. The cluster spans about 58 light-years and contains several tens of thousands of stars. Dark lanes of dust are visible crossing the cluster's face — unusual for a globular.

Located about 3 degrees south-southwest of Zeta Ophiuchi. In binoculars it appears as a small, faint fuzzy patch. A 4-inch telescope shows a round, grainy glow. An 8-inch telescope at 150x begins to resolve individual stars due to the cluster's loose structure. Look for the dark dust lanes threading across the cluster — these are best seen in larger apertures. Best observed from June through August.

Discovered by Pierre Mechain in April 1782. It was the last object added to the Messier catalog, not included until 1947 by Helen Sawyer Hogg. In between, it was independently found by William Herschel in 1793.