M15

The Great Pegasus Cluster is one of the densest globular clusters known, located about 33,600 light-years away in Pegasus. It contains over 100,000 stars packed into a sphere about 175 light-years across, with an extremely dense core that may harbor a central black hole. M15 has undergone 'core collapse' — its core has contracted to an extraordinarily dense state.

Located about 4 degrees northwest of Enif (Epsilon Pegasi), the nose of the winged horse. Visible in binoculars as a bright, star-like fuzzy point. A 4-inch telescope at 100x shows a bright, intensely concentrated glow. An 8-inch telescope resolves stars in the outer regions while the core remains a brilliant, unresolved blaze. The planetary nebula Pease 1 within the cluster is visible in large amateur scopes. Best observed from August through November.

Discovered by Jean-Dominique Maraldi on September 7, 1746. Charles Messier cataloged it in 1764. In 1928, the planetary nebula Pease 1 was discovered within M15 — only four planetary nebulae are known in globular clusters.