Globular Cluster M 71 in Sagittarius

Globular cluster M 71 in the constellation Sagitta.

The cluster was discovered by Jean-Philippe de Chéseaux in 1745 and was included in Charles Messier’s catalog of comet-like objects in 1780.

M 71 is located 13,000 light-years from Earth and spans 27 light-years. The irregular variable star Z Sagittae belongs to this cluster.

This cluster is observed in late summer to early autumn, often together with M 27—the “Dumbbell Nebula.” In a telescope with an aperture of 200–250 mm, this very sparse globular cluster resolves into numerous stars forming a V-shaped pattern resembling the tip of a spear. With a smaller aperture, most of the “unresolved” stars create a diffuse background glow in the cluster region.

Even 40–50 years ago, there was debate about the nature of M 71—whether it was a globular or an open cluster. However, the prevailing view remains that it is indeed a globular cluster.