The nearby Andromeda Galaxy has a supermassive one of these at its center
... Because of 
its proximity to us, Andromeda  or M31  is an excellent place to study just ... of 
just how these supermassive black holes act in the later stages of spiral galaxy 
life... [DOC] [TLE] Supermassive Black Hole Sagittarius A* | NASA [PAR] Aug 29, 2013 ...