M69

M69

Messier 69 or M69, also known NGC 6637, is a globular cluster in the southern constellation of Sagittarius. It can be found 2.5° to the northeast of the star Epsilon Sagittarii and is dimly visible in 50 mm aperture binoculars. The cluster was discovered by Charles Messier on August 31, 1780, the same night he discovered M70. At the time, he was searching for an object described by Nicolas-Louis de Lacaille in 1751–2 and thought he had rediscovered it, but it is unclear if Nicolas-Louis de Lacaille actually described M69.

This cluster is at a distance of about 28,700 light-years away from Earth and 5,200 ly from the Galactic Center, with a spatial radius of 45 light-years. It is a relatively metal-rich globular cluster that is a likely member of the Galactic bulge population. M69 has a mass of 2.0×105 M☉ with a half-mass radius of 11.6 ly, a core radius of 29.2 ly, and a tidal radius of 91.9 ly. The center of the cluster has a luminosity density of 6,460 L☉·pc−3. It is a close neighbour of globular cluster M70, with perhaps only 1,800 light-years separating the two objects.