Supermassive Black Hole Kicked Out of Its Galactic Core by Powerful Gravitational Waves

Astronomers revealed that powerful gravitational waves are capable of kicking out supermassive black holes from the center of a galaxy.

Their findings, described in a paper to be published in the March 30 issue of Astronomy and Astrophysics, showed that the gravitational waves created by two merging black holes at the center of the galaxy have the propulsive energy to drive away a supermassive black hole. The researchers estimate that the propulsive energy necessary to do such feat is equivalent to the energy produced by 100 million supernovas exploding simultaneously.

"When I first saw this, I thought we were seeing something very peculiar," said team leader Marco Chiaberge of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in a statement.

Chiaberge and his colleagues first noticed that something is unusual with a galaxy eight billion light-years away when Hubble images taken in visible and near-infrared light showed a bright quasar located far from the center of the galaxy. Quasars are intense, compact gushers of radiation that can outshine an entire galaxy. They also serve as the energetic signature of black holes.

Calculations showed that the black hole is moving away from the center of the galaxy at 4.7 million miles an hour, fast enough to escape the galaxy and roam the universe in approximately 20 million years. The team calculated that the black hole had already travelled over 35,000 light years from the center, which is more than the distance between our sun and the center of Milky Way.

The researchers devised a likely scenario how the black hole got kicked out of its original location. In their theory, the researchers believe that two galaxies collided with each other and formed an elliptical galaxy. As the two galaxies merge, their black holes settle in the center and whirl around each other, creating gravitational waves.

The researchers noted that the if the two black holes don't have the same mass and rotation rate, it is highly possible that they emit gravitational waves more strongly along one direction. When the black holes finally collide, they stop producing gravitational. The newly merged black hole then recoils in the opposite direction of the strongest gravitational waves and shoots off like a rocket.

Another unlikely explanation for the out of place quasar is that the Hubble images created an illusion that it belongs to the galaxy. It is possible that the quasar belongs to another galaxy behind the galaxy they were observing.