Globular Star Cluster M-71 (NGC 6838)

Globular Cluster, M-71
This image was taken with an ST-9E CCD camera (with AO-7) thru Kopernik's 20-inch F/8.1 telescope. This was a 21 minute exposure (LRGB= 9:4:4:4 minutes). The field of view is about 9x9 arc minutes.

Today most astronomers consider M-71 to be a very loose globular star cluster that is a part of a small and unique group of globulars with metal-rich stars. This class of "disk population globular clusters" includes the famous southern sky cluster NGC 104 (47 Tucanae). It's stars exhibit characteristics that are not explained by any current theory of stellar evolution, and the cluster remains a subject of active research.

Discovery: M-71 was probably first observed by de Cheseaux as early as 1746, but his record was lost. J.G.Koehler independently discovered it at Dresden about the year 1775, and in June 1780 P.Mechain rediscovered it.