Messier 15 is a gathering of 100,000 very old stars that orbits the center of the Milky Way. It
is one of the densest globular clusters known, with most of its mass concentrated at its core.
It could also hide a rare type of black hole or a collection of dark neutron stars.
Messier 15 is located 35,000 light-years away in the constellation of Pegasus, The Winged Horse). It is one of the oldest globular clusters known, with an age of around 12 billion years.
In a new Hubble image, very hot blue stars and cooler golden stars are seen swarming together, becoming more concentrated towards the cluster's bright center.