Messier 75 (also known as NGC 6864) is a globular cluster in the western part of Sagittarius.
M 75 was probably first seen by Pierre Mechain in August of 1780, and confirmed by Messier two months later. William Herschel first resolved M 75 into stars in 1784, and described it as a "miniature of M 3."
Messier 75 is a moderately faint, magnitude 8.5 globular cluster, with a 6.8' diameter halo that contains a bright core. As one of the more compact, concentrated globulars, larger scopes are required to resolve it into stars. They show a granular halo and resolve numerous stars around the periphery. The outlying stars are rather uniformly distributed in all directions, but the core is concentrated and remains unresolved.
M 75 lies at a distance of 67,500 light years, and is one of the more remote Messier globulars. Lying well beyond the Galactic center, from which it is 47,600 light years distant, its apparent size translates to a true diameter of some 130 light years. It contains at least 100,000 stars, and is one of the more densely concentrated globular clusters known. The absolute magnitude of M 75 is about -8.5, or some 180,000 times the luminosity of our Sun.