Recoiling black hole
Every large galaxy is supposed to have a supermassive blackhole at its centre. When backholes merge, they release gravitational waves. When the waves released in one direction is stronger than in the other, one of the black holes is ejected out of its galaxy into the opposite direction. This blackhole is called ‘recoiling black hole’. Abell 2261 is a galactic cluster located some 2.7 billion light years from the Earth and it should have a black hole that is some 100 billion times as heavy as our Sun. However, the scientists have been unable to find it and are reasoning that it was ejected out of its galaxy.