Night Thirtyfour - The Pegasus Cluster, M15

This is a globular cluster located in the constellation Pegasus. It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier's catalogue of comet-like objects in 1764. M 15 is about 35,700 light-years from Earth, and 175 light-years in diameter. It has an absolute magnitude of −9.2, which translates to a total luminosity of 360,000 times that of the Sun. Messier 15 is one of the most densely packed globulars known in the Milky Way galaxy. Its core has undergone a contraction known as "core collapse" and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole. Home to over 100,000 stars,the cluster is notable for containing a large number of variable stars (112) and pulsars. This cluster is host a rare type of black hole at its center: an intermediate-mass black hole. Supermassive black holes are found at the center of galaxies and can be billions of times more massive than the sun. More diminutive “stellar” black holes, on the other hand, are on the order of 10 solar masses. The black hole thought to exist at the center of M15, however, is 4,000 times the mass of the sun.