Scientists are baffled by a missing supermassive black hole which should by normal expectations sit in the centre of a distant galaxy.
Instead, according to researchers at a handful of North American universities, there appears to be something highly unusual about the bright cluster galaxy A2261-BCG.
They believe it is the first ever example of a so-called “recoiling” black hole – a black hole that was ejected from the centre of the galaxy by a powerful force, and is now mysteriously floating through space.
The galaxy is one of 25 within the Abel 2261 cluster spotted by Hubble. Pic: NASA
The nature of these black holes has been described in a study which will be published by the American Astronomical Society journal, led by Dr Kayhan Gultekin at the University of Michigan.
Dr Gultekin studied A2261-BCG, located about 2.6 billion light years from Earth, as it has a large and flat stellar core, as revealed by the Hubble Space Telescope, making it a potential candidate for a galaxy with a missing black hole.
New observations his team captured using the Chanda X-ray observatory have confirmed that there are no X-ray emissions from the centre of the galaxy nor in any of the four off-centre stellar knots, which would indicate the black hole’s location.
Speaking to online technology magazine Motherboard, Dr Gultekin said: “I was very sceptical and thought we would see something at the very centre. But that turned out not to be the case. It turned out to not be in any of these locations.”
The team believes there is a chance that there is a “very stealthy black hole” in the galaxy, one that is relatively dim compared to other supermassive black holes and thus incredibly difficult to detect.
However the possibility that the black hole is missing is even more exciting as it would have been ejected by the recoil caused when two supermassive black holes merged during a galactic collision.
Supermassive black holes have never been observed merging and finding evidence supporting this hypothetical scenario would be an enormous breakthrough for astronomy, revealing details about the nature of the universe that couldn’t be observed in any other way.
Smaller black holes are known to merge because they produce gravitational waves – ripples in spacetime that were first proposed in 1905 but not directly observed until 2016.
Late last year scientists announced they had detected the most massive source of gravitational waves which had ever been recorded, although they said they weren’t completely sure what caused it.
“What excites me the most is learning about supermassive black holes through gravitational waves,” Dr Gultekin told Motherboard.
“We need to know for certain that they are merging and this would be one way of showing that that’s happening,” he added.
His team hopes that future space telescope missions from NASA and the European Space Agency will be able to search the galaxy for more information.