Japanese astronomers have learned that merging galaxies can contain at least a pair of active and luminous supermassive black holes. Typically, only one of the two black holes are activated like this, leading the astronomers to speculate that something unique is happening in the environment to get them going.
Astronomers theorize that collisions and mergers of small gas-rich galaxies result in the formation of massive galaxies. At the center, these objects contain a supermassive black hole (SMBHs) weighing more than one-million solar masses. When material accumulates onto a SMBH, the accretion disk surrounding it becomes extremely hot from the release of gravitational energy and it becomes very bright.