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A standard black hole continues to slip through the nets of astronomers.
Supermassive black holes are believed to be lurking deep within most, if not all, galaxies. Our own Milky Way has one as massive as 4 million suns, for example, and M87 – the only black hole ever photographed directly – tips the scales at 2.4 billion solar masses.
The large galaxy at the heart of the Abell 2261 cluster, which is about 2.7 billion light years from Earth, is expected to have an even larger central black hole – a light-engulfing monster that weighs up to 3 billion to 100 billion suns, astronomers estimate from the mass of the galaxy. But the exotic object has so far escaped detection.
Related: First historical images of black hole show Einstein was right (again)
For example, researchers previously looked for streaming x-rays from the center of the galaxy, using data collected by NASA. Chandra X-ray Observatory in 1999 and 2004. X-rays are a potential signature of the black hole: when material falls into the mouth of a black hole, it accelerates and heats up tremendously, emitting lots of high-energy x-rays. But this hunt did not reveal anything.
Now, a new study has conducted even more in-depth x-ray research in the same galaxy, using Chandra’s observations from 2018. And this new effort hasn’t just looked at the center of the galaxy; he also considered the possibility that the black hole was thrown backcountry after a monster galactic fusion.
When black holes and other massive objects collide, they cause ripples in space-time called gravitational waves. If the emitted waves are not symmetrical in all directions, they could end up pushing the fused supermassive black hole away from the center of the newly enlarged galaxy, scientists say.
Such “receding” black holes are purely hypothetical creatures; no one has definitely spotted one to date. Indeed, “we do not know if the supermassive black holes come close enough to each other to produce gravitational waves and merge; so far, astronomers have only checked for mergers of much smaller black holes, ”NASA officials wrote in a report. new study statement.
“The detection of receding supermassive black holes would encourage scientists to use and develop observatories to search for gravitational waves from the fusion of supermassive black holes,” they added.
The central Abell galaxy 2261 is a good place to hunt such a unicorn, the researchers said, as it carries several possible signs of a dramatic merger. For example, the observations of The Hubble Space Telescope and the Subaru Ground Telescope show that its core, the region of highest star density, is much bigger than expected for a galaxy its size. And the densest star patch is about 2,000 light years from the center of the galaxy – “remarkably distant,” NASA officials wrote.
In the new study, a team led by Kayhan Gultekin of the University of Michigan found that the densest concentrations of hot gases were not found in the central regions of the galaxy. But the Chandra data did not reveal any significant x-ray source, either in the galactic nucleus or in large star clusters further afield. So the mystery of the missing supermassive black hole persists.
This mystery could be solved by Hubble’s successor – the great and mighty NASA James Webb Space Telescope, scheduled for launch in October 2021.
If James Webb does not spot a black hole in the heart of the galaxy or in one of its larger star clusters, “then the best explanation is that the black hole has retreated well out of the center of the galaxy,” wrote NASA officials.
The new study was accepted for publication in a journal of the American Astronomical Society. You can read it for free on the online pre-print site arXiv.org.
Mike Wall is the author of “Over there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book on the search for extraterrestrial life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
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