Some black holes at the centers of galaxies have a buddy but detecting these binary pairs isn't easyBinary supermassive black holes at galaxy centers are crucial for understanding galaxy formation and mergers.
An Unusually Shaped Space Object Long Puzzled Astronomers - What It Turned Out to Be Was Truly UncannyGliese 229B, once thought to be a single brown dwarf, is actually a binary system of two distinct objects.