M15 • NGC 7078 • Globular Cluster

M15 is one of the most compact and densely concentrated globular clusters in the Milky Way. It contains several hundred thousand stars packed into a bright core that has undergone core collapse, resulting in an extremely dense central region. The cluster is rich in variable stars, including RR Lyrae variables, and also hosts several planetary nebulae — most notably Pease 1, one of the very few planetary nebulae known to exist inside a globular cluster. M15’s high stellar density and striking structure make it a favourite target for deep astrophotography.