Watch: Black Holes May Be Wandering Around In Space
A supermassive black hole with a mass 3 million times that of our sun is wandering through space on its own at a speed of 110,000 miles an hour, scientists have revealed.
The "restless" black hole is 230 million light years from Earth and sits at the heart of a galaxy called J0437+2456.
The Harvard researchers believe the moving black hole may be the product of a merger between two huge black holes.
It could even be part of a binary pair of black holes, with an invisible "twin" that we have not yet detected, the researchers say.
Their results are published in The Astrophysical Journal.
Read more: There might once have been life on the moon
Lead author Dominic Pesce, an astronomer at the Center for Astrophysics, said: "We don't expect the majority of supermassive black holes to be moving; they're usually content to just sit around.
"They're just so heavy that it's tough to get them going.
“Consider how much more difficult it is to kick a bowling ball into motion than it is to kick a soccer ball – realising that in this case, the 'bowling ball' is several million times the mass of our sun.
“That’s going to require a pretty mighty kick."
The team found the "moving" black hole by comparing the relative velocities of supermassive black holes and their galaxies.
Pesce said: "We asked: Are the velocities of the black holes the same as the velocities of the galaxies they reside in?"
"We expect them to have the same velocity. If they don't, that implies the black hole has been disturbed."
The team looked at 10 distant galaxies and their black holes, looking for laser-like beams of radio lights known as masers, produced by water in the black holes’ accretion discs – the spiral structures that spin inward towards the black hole.
The technique helped the team determine that nine of the 10 supermassive black holes were at rest – but one stood out and seemed to be in motion.
The team are still unsure of what is making it move, they say.
Jim Condon, a radio astronomer at the National Radio Astronomy Observatory, said: "We may be observing the aftermath of two supermassive black holes merging.
"The result of such a merger can cause the newborn black hole to recoil, and we may be watching it in the act of recoiling or as it settles down again."
Another possibility is that the black hole may be part of a binary system, says Pesce.
He says: "Despite every expectation that they really ought to be out there in some abundance, scientists have had a hard time identifying clear examples of binary supermassive black holes.
"What we could be seeing in the galaxy J0437+2456 is one of the black holes in such a pair, with the other remaining hidden to our radio observations because of its lack of maser emission."
Watch: Scientists discover a black hole-powered object 13 billion light years away