Black holes are mysterious and fascinating entities endowed with incredible powers. With its huge gravitational pull, a black hole attracts everything that comes near it. No light penetrates out of it. Therefore, the gravity giants cannot be observed directly with optical telescopes. Every galaxy probably has a black hole at its center that holds the structure together around itself – normally.
Despite an intensive search, astronomers have not yet discovered such a black hole in the distant galaxy with the cryptic name A2261-BCG. In the center of this brightest galaxy of the galaxy cluster Abell 2261 there is a gap. Measured by its mass, however, the cluster of stars about three billion light-years away should have one of the largest known supermassive black holes. Expert:ins estimate it to be at least ten billion solar masses.
Missing black hole in galaxy A2261-BCG puzzles astronomers
Kayhan Gültekin of the University of Michigan and his team also wanted to find out more about the missing black hole and went in search of it. They published their findings at the American Astronomical Society. Using the Chandra X-ray telescope, the astronomers led by Gültekin scanned the center of the galaxy for X-rays to determine whether or not there was a black hole there.
X-rays are typically emitted by hot gas swirling around black holes. In addition to the center, four star clusters near it were also examined. The site where the Very Large Array telescope in New Mexico had detected radio emissions in previous studies was also scanned for radiation. At that time, the radio emissions had turned out to be 50 million years old and were therefore no evidence for the current presence of a black hole.
Search for supermassive black hole: evidence of collision
However, the astronomers did not find anything. “Our analyses show no point sources of X-ray emission in the center of A2261-BCG, neither in the optical center of the galaxy, nor in the star clusters, nor at the origin of the radio emission,” the researchers are quoted by “scinexx.de.” The astronomers exclude a falsification of the data. The view was not shrouded by dust clouds or shielding gases. The view of the galaxy was “dust-free”.
So, according to Gültekin and his team, either there is no black hole in the core of the distant galaxy or it is collecting very little matter. However, the researchers:inside suspect that the first variant is true. “Although the absence of evidence is not proof of an absence, our observations fit that there is no black hole in the central region of this galaxy.”
Galactic catastrophe may have catapulted black hole out of galaxy
However, the supermassive black hole could also have been ejected from the core of galaxy A2261-BCG. Such a thing can happen when two galaxies collide and their central black holes merge. In this process, gravitational waves propagate in the universe. The recoil with a speed of up to several thousand kilometers can cause the black hole to be pushed or displaced away from the center. Evidence for such a process has already been collected. However, evidence for the existence of such a black hole does not yet exist.
Supermassive black hole at center of distant galaxy has gone missing https://t.co/LnUzvE7RYY pic.twitter.com/dDumbaum80
– New York Post (@nypost) January 11, 2021
Nevertheless, such a galactic catastrophe could also have taken place in the galaxy A2261-BCG about ten million years ago. Some indications speak for it according to the researchers. On the one hand the unusual mass and density of the center and the curious appearance of the star cluster with its large gap in the core. In addition that its center is shifted approximately 2,200 light-years in relation to the geographical center.
Whether the black hole is possibly still to be found somewhere in the core area or it was ejected completely from the central area of the galaxy, could still James Webb space telescope find out, whose resolution is higher than the telescopes used so far. So the mystery about the galaxy A2261-BCG is not solved yet.