A “hiccup” black hole has been observed for the first time at the center of a galaxy 800 million light-years away from Earth.
For four months, it emitted beams of gas every 8.5 days, probably due to the presence of a second, smaller black hole around it that periodically crossed its accretion disk, a possibility that until now had only been predicted theoretically.
This is according to a study published in the journal Science Advances by astronomers from the Massachusetts Institute of Technology (MIT), in the United States, in collaboration with scientists from the Czech Republic and the University of Rome Tor Vergata. If confirmed, this discovery could change the concept of the black hole accretion disk, which until now was considered to be a relatively uniform body of gas rotating around the event horizon.
However, the results of the new study suggest that, in some cases, this disk could harbor other black holes and even stars.
The research is based on observations made by a network of 20 robotic telescopes (All Sky Automated Survey for SuperNovae, Asas-Sn), which are always in search of supernovae and other transient phenomena.
In December 2020, the equipment identified a glow coming from a galaxy 800 million light-years away that until then had remained silent. Subsequent observations carried out with NASA’s Nicer X-ray telescope, mounted on board the International Space Station (ISS), made it possible to detect a periodicity of 8.5 days in the emissions. The signal was similar to that seen when a planet passes in front of its star, temporarily blocking the light.
Seeking an explanation for this unprecedented phenomenon, MIT researchers, guided by Dheeraj Pasham, contacted Czech physicists who had predicted the possibility of a supermassive black hole at the center of a galaxy being orbited by a second, smaller black hole that periodically passes through the accretion disk, a phenomenon that would cause the release of gas beams.
According to calculations, the supermassive black hole has a mass equal to 50 million times that of the Sun, while the smallest has between 100 and 10 thousand solar masses. In December 2020, a third object entered the scene, likely a star that came too close and ended up being torn apart by the gravity of the larger black hole. The sudden influx of stellar material temporarily illuminated the accretion disk.
For four months, the black hole feasted on stellar debris; however, the second black hole continued to orbit it, periodically crossing the accretion disk, thus ending up generating the beams detected by Nicer.
“This result calls into question our traditional image of an accretion disk from a supermassive black hole. A scenario with a disk and possibly many objects like black holes and stars passing through it may be more realistic than a simple image of a disk gas”, explained Fabrizio Tombesi, from the University of Rome Tor Vergata.
