A group of scientists from Durham University and other scientific organizations, led by Professor James Nightingale, announced the discovery of one of the heaviest black holes in the universe. As follows from an article published on March 29 in the journal Monthly Notices of the Royal Astronomical Society, it is located at a distance of more than 2 billion light years from Earth in the center of the galaxy Abell 1201 and has a mass equal to 30 billion solar masses.
Since it is impossible to measure the movements of individual stars at such a distance, the effect of gravitational lensing helped to detect a giant black hole. Abell 1201 acts as such a gravitational lens for an even more distant galaxy, more than 6 billion light-years away. A large arc is observed near the lens – this is a deformed image of the source galaxy. The image is created by the total mass of the Abell 1201.
However, astronomers noticed a small image on the other side of the lens – opposite the arc and much closer to the center of Abell 1201. Modeling the mass distribution in the gravitational lens, astronomers came to the conclusion that the second image can be best described if placed at the center of the Abell galaxy 1201 black holes are 30 billion times heavier than the Sun.
A black hole with such a mass made astrophysicists think again about the mechanism of hole formation, which is still unclear. The discovery of Nightingale and his co-authors showed how inactive (that is, not intensively interacting with luminous matter) supermassive black holes can be detected; undoubtedly, in the coming years we will find many objects of this type.
A black hole is an object so massive and at the same time compact that not even light can escape from it. Therefore, you cannot see it directly. However, one can see the effects caused by a black hole: one can observe the movement of stars around it and the radiation of an accretion disk (a rotating disk of matter falling onto a black hole – due to friction in the disk, it is very hot). The motion of stars and clouds of gas around a black hole can be used to measure its mass. However, such observations are available only for relatively close black holes. At the same time, scientists are interested in the masses of distant black holes, in particular because supermassive black holes located in the centers of galaxies play a significant role in their formation, and the farther a galaxy is from us, the more “young” we observe it.
To understand what gravitational lensing is, you need to remember the Eddington experiment. In 1919, he measured the deflection of the rays of stars in a gravitational field as they pass close to the solar disk. If the light from the source passes near a massive galaxy (which in this case will be a gravitational lens), the same effect causes the images of stars or entire galaxies behind it to be stretched and distorted, and there may be several images. If the light source is exactly behind the gravitational lens, then its image will "spread out" into a ring, called the Einstein ring.