Messier 15 (M15) is a globular cluster of stars in the constellation Pegasus, located about 32,620 light-years from Earth. It is one of the oldest known globular clusters, estimated to be around 12.5 billion years old. M15 is also one of the densest globular clusters, with most of its mass concentrated at its core.
M15 is part of a halo of nearly 150 globular clusters that surround the Milky Way galaxy. Each cluster is a spherical group of hundreds of thousands of ancient stars, with M15 containing both hot blue stars and cooler golden stars. The brightest stars in M15 have an apparent magnitude of 12.6, an absolute magnitude of -2.8, and a luminosity that is 1,000 times that of the Sun.
