Contact StarDate | About StarDate | Friends of McDonald | Sign up for SkyTips

How are black holes named?

There is no unified naming system for black holes. The supermassive black holes in the cores of galaxies are named for the galaxies. A name like M31 indicates that the galaxy was catalogued by Charles Messier in the 1700s. A name that begins with "NGC" is listed in the New General Catalog, which was compiled in 1888 and expanded in later years. A few black holes are catalogued by their constellation and the order in which they were discovered; Cygnus X-1 was the first X-ray object discovered in Cygnus, for example. And many black holes are identified by the instrument or survey that discovered them and their position in the sky. XTE J1118+480 was discovered by the Rossi X-Ray Timing Explorer (XTE) satellite, and is at the celestial coordinates 1118+480. GRO J1655-40 was discovered by the Compton Gamma-Ray Observatory, and so on.