M107 - NGC 6171

Messier 107 (NGC 6171) is a globular cluster located approximately 20,900 light-years from Earth in the constellation Ophiuchus. It was discovered by Pierre Mechain in 1782 and was one of the last objects added to the expanded Messier catalog. M107 is a relatively loose globular cluster with a Shapley-Sawyer concentration class of X, indicating low concentration, and it spans about 80 light-years in physical diameter. The cluster has a visual magnitude of about 7.9 and contains tens of thousands of stars. M107 is notable for its many dark voids and lanes visible within the cluster, created by intervening dust clouds in the plane of the Milky Way. This gives M107 a somewhat patchy or mottled appearance compared to more symmetrical globular clusters, as the foreground dust blocks light from portions of the cluster. The cluster lies close to the galactic plane at a galactic latitude of only about +23 degrees, which explains the significant dust interference. M107 has a moderately low metallicity and is estimated to be about 13.9 billion years old, making it one of the older globular clusters. It contains at least 25 known variable stars, including RR Lyrae types. M107 is located about 3 degrees south of the star Zeta Ophiuchi and about 3 degrees northwest of M62. In binoculars, M107 appears as a faint, fuzzy spot. A 4-inch telescope shows it as a round, granular glow, while 6-inch and larger telescopes can begin to resolve individual stars across the face of the cluster due to its relatively loose concentration. Under good conditions, an 8-inch telescope provides an attractive view with many resolved stars.

M107 spans about 80 light-years in diameter and lies approximately 20,900 light-years from Earth with a loose concentration class of X.