Black holes are some of the most interesting phenomena in the universe. If you want to know what it is, then read this post: What is a black hole? And now we are learning something new and interesting about black holes and the laws of the universe.
The black holes in the center of galaxies are also known as supermassive black holes. Black holes are formed when a star with a mass at least 5 times the mass of the Sun depletes its fuel and, due to gravitational collapse, falls into itself, forming a black hole. Supermassive black holes can contain hundreds of millions of star masses, like our Sun.
Astronomers are now pretty confident that these supermassive black holes are at the center of nearly every galaxy in the universe. In addition, the mass of these black holes is somehow related to the mass of the rest of the galaxy. They are formed in close contact with each other.
A group of scientists from the United States, Germany and Spain found that supermassive black holes stop the formation of stars, which occurs in large galaxies.
In young galaxies, new stars appear very quickly, but as soon as the galaxy is completely formed, this process stops. This is influenced by the supermassive black hole, which is at the center of every large galaxy and which is millions of times larger than the Sun. It has gravitational effects on stars in the galaxy and sometimes amplifies radiation from the galaxy's active nucleus. Scientists believe that this energy turns off star formation, heating and dissipating gas that would turn into a star once it cools.
The authors studied massive galaxies where the mass of the central black hole has already been measured. To understand how these galaxies evolved, scientists analyzed their emission spectrum using the Hobby-Eberley telescope. When comparing the results, the authors saw that the formation processes of galaxies with central black holes of different masses are very different. Astronomers found that these differences were related only to the mass of the black hole, and not to the size of the galaxy or its morphology.
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“In galaxies of the same mass, but with different masses of their central black holes, the process of star formation ended earlier where the black holes were more massive, and vice versa. This means that the appearance of stars in galaxies with a lower mass of central black holes took longer,”- said Ignazio Martin-Navarro, Ph. D. in physics and mathematics, at the University of California at Santa Cruz.
The authors note that previously it was not possible to achieve such results, because the time of the course of all processes is very different: stars can form over hundreds of millions of years, while the release of energy from the active galactic nucleus can occur in a shorter time. Such nuclei differ from each other, and their characteristics depend on many factors: the size of the black hole, the level of accretion of material falling onto the black hole, and many others.
Black holes without stars
Supermassive black holes are found at the center of many galaxies. With the help of the processes occurring near them: the formation of an accretion disk from the attracted matter and relativistic jets of plasma - jets, one can explain, for example, the most powerful radiation of quasars. In the last decade, supermassive black holes have been discovered, many of which are billions of times more massive than the Sun, with large Doppler redshifts. This means that they existed in our Universe only 800 million years after the Big Bang.
However, modern astrophysics believes that black holes arise as a result of the evolution of stars, when at the last stage the remnant of a massive star, which has lost its thermonuclear fuel, contracts, collapses into a small body with monstrous gravity. Then they can grow, absorbing the surrounding matter. The presence of such young and very massive black holes casts doubt on such a scenario of formation, because then there were still not enough stars that had passed the entire evolutionary path.
Astrophysicists at Western University of Canada have developed a theory of the formation of supermassive black holes in the early Universe as a result of direct collapse of matter without the formation of stars. They wrote about this in the Astrophysical Journal Letters.
In their opinion, in the early Universe there was a short period of time when supermassive black holes could form and grow rapidly without preliminary formation of a star, simply pulling the surrounding plasma into the primary clot - the "germ". Then, at some point, the changed conditions stopped this process. In this case, black holes are formed very quickly within an extremely short time interval. The scenario of such a "direct collapse" results in initial black hole masses much larger than in the standard "stellar remnant" scenario.
Such a scenario of the formation of supermassive black holes makes it possible to explain their existence and huge masses already at a very early stage in the evolution of our Universe.