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Hubble telescope spots 'runaway' black hole

The black hole, shot out of a distant galaxy, is the first of its kind.

NASA, ESA, and M. Chiaberge (STS

Astronomers using NASA's Hubble Space Telescope have observed a supermassive black hole with a mass one million times that of our Sun hurtling away from its parent galaxy. It's the first confirmed case out of several suspected "runaway black holes," which required an immense amount of energy to get launched from the center of its galaxy. How much?

"We estimate that it took the equivalent energy of 100 million supernovae exploding simultaneously to jettison the black hole," said Stefano Bianchi of Roma Tre University, co-author of the study announcing the phenomenon. According to their theoretical model, gravitational waves generated by two other black holes merging 1-2 billion years ago might have sent the supermassive one hurtling spaceward.

This illustration shows how two supermassive black holes merged to form a single black hole which was then ejected from its parent galaxy. Panel 1: Two galaxies are interacting and finally merging with each other. The supermassive black holes in their centres are attracted to each other. Panel 2: As soon as the supermassive black holes get close they start orbiting each other, in the process creating strong gravitational waves. Panel 3: As they radiate away gravitational energy the black holes move closer to each other over time and finally merge. Panel 4: If the two black holes do not have the same mass and rotation rate, they emit gravitational waves more strongly along one direction. When the two black holes finally collide, they stop producing gravitational waves and the newly merged black hole then recoils in the opposite direction to the strongest gravitational waves and is shot out of its parent galaxy.

The researchers had noticed that the black hole's energetic signature, known as a quasar, was located far from its expected place at the center of its home galaxy, named 3C186. It had already moved 35,000 light-years away, the team calculated, which is farther than our Sun's distance from the center of the Milky Way. The supermassive black hole continues to move at 7.5 million kilometers per hour, a speed that would get you from the Earth to the Moon in three minutes.