NASA Monitors Collision Course of Supermassive Black Holes.

NASA’s Chandra X-ray Observatory has detected two pairs of supermassive black holes on collision courses in dwarf galaxies, which is the first evidence of such an impending encounter. By definition, dwarf galaxies contain stars with a total mass less than 3 billion Suns — or about 20 times less than the Milky Way. Astronomers have long suspected that dwarf galaxies merge, particularly in the relatively early Universe, in order to grow into the larger galaxies seen today. The details of merging black holes and dwarf galaxies may provide insight to our Milky Way’s own past.