M71

Messier 71 (M71), also designated NGC 6838, is a globular cluster in the Milky Way halo. It lies in the constellation Sagitta and is estimated to be about 13,000 light-years from the Sun, or roughly 4 kiloparsecs. With an apparent magnitude near 6.0, M71 is visible with binoculars under dark skies, and it spans about 9 arcminutes in diameter, making it a small but detectable cluster in small-telescope fields.

Stellar population: M71 is relatively metal-rich for a globular cluster, having a measured metallicity [Fe/H] around −0.7 to −0.8 dex. Age estimates place it at about 12 to 13 billion years, consistent with a classic old globular cluster formed early in the Milky Way.

Discovery and designation: The object was listed by Charles Messier in 1780 as part of his catalog of comets and non-comet nebulae. Its other designation, NGC 6838, comes from the New General Catalogue.

Structure and research: M71 is somewhat less concentrated than the most compact globular clusters, a trait that aids the detection of individual stars with modern telescopes. It has been the subject of studies on stellar evolution and globular cluster dynamics, including investigations of its stellar populations and chemical composition.