There is no exact definition of the term “black hole” in physics. Scientists interpret this concept in different ways, but they agree that this is a region of space with a very strong gravitational pull. This means that all objects, objects and phenomena that fall into a black hole cannot return. All black holes have a boundary called an event horizon. A black hole attracts matter and forms an accretion disk around it. This accretion disk is a gigantic structure that rotates rapidly and emits light due to the interaction of friction and gravity. A black hole that rotates in this way is called a spheroid. However, there are other holes that cannot be rotated, and they are called spherical surfaces.
There are various types of black holes. A black star with stellar mass. These objects are no larger than three solar masses. A black star of intermediate mass. This is an object that has grown in size due to absorption from a gas cluster in a paired star system or from a neighboring star. The mass of such a black hole is 10 to several tens of times the mass of the Sun. Supermassive black hole. The mass of these objects reaches 105-1011 solar masses. Supermassive black hole. Currently, only two representative species of this species are known. The first object with a mass of 40 billion solar masses is located in the galaxy Holm 15A. The second black hole is located in the constellation Hanabi – it is TON 618 and its mass is equivalent to 66 billion solar masses.
Why are black holes called so? These cosmic objects are not named for their color, but for their special property that black holes can only absorb radiation. These objects are usually called black because they are invisible and emit no light. Black holes are known to exist only when surrounded by interacting matter, such as gas or nearby stars. Scientists suspect that white holes, the opposite of black holes, also exist in the universe. If a black hole is a place where nothing returns, a white hole is a place where nothing returns. However, to date the existence of such objects has not been proven.
How did scientists learn about the existence of black holes? The idea of the existence of black holes was first proposed by British scientist John Michel in 1784. He believed that there were objects in the universe with gravitational forces so strong that a speed faster than the speed of light was needed to overcome them. At the time, this theory received no attention at all. Only 121 years later, Albert Einstein proposed the theory of relativity, which views gravity as the curvature of spacetime. In 1916, German astronomer Karl Schwarzschild actually described the gravitational field of a non-rotating black hole, and 57 years later, New Zealand physicist Roy Carr proved that this mysterious object also rotates. Scientists first discovered “collapse bodies”, then called black holes, in 1964. This celestial body was located in the constellation Cygnus, and radio waves were being emitted from it. The term “black hole” was first used three years later by American physicist John Wheeler. And the first photos of this physical phenomenon appeared only in 2019. An international team of astronomers used eight radio telescopes to obtain the most detailed images of the central object of galaxy M87.
How do scientists find black holes in the universe? In the 1960s, scientists made their first attempts to search for black holes. Until then, there were no telescopes that could provide high-quality images. Physicists hypothesize that large stars form in pairs, one of which eventually becomes a black hole. Therefore, scientists first tried to detect a cosmic object rotating around another “invisible” object and use calculations to calculate the black hole. However, no single black hole has ever been discovered using this method. Physicists have suggested that black holes near stars can use their gravity to pull them closer. In the late 1960s and early 1970s, rockets were fitted with X-ray detectors that could actually detect bright radiation from the gas circulating around black holes. This is how the first black hole was discovered. To confirm the existence of black holes, scientists also studied quasars, active galactic nuclei in the early stages of development that emit bright light. During their observations, they discovered that these objects contain supermassive black holes. According to astrophysicist Sergei Popov, this is currently the most obvious way to search for black holes, and new mysterious objects are increasingly being discovered this way. These objects can be discovered in space by detecting the gravitational wave bursts that occur when two black holes merge. Moreover, these objects can greatly distort the space around them and increase the brightness of stars, unwittingly giving signals to astrophysicists.
How do black holes form and disappear? Scientists have identified several reasons for the formation of black holes. According to one of them, these objects were formed as a result of the compression of very massive stars under the influence of gravity. According to the second hypothesis, it is not a single star that “collapses” under its own weight, but a part of the galaxy. Physicists say these objects could have formed as the universe expanded even after the Big Bang. Such objects are also called primordial black holes. Finally, physical phenomena can occur during high-energy nuclear reactions. Similar reactions are used to study particles in the Hadron Collider. It is not known for sure whether black holes will disappear. There is a hypothesis that black holes lose mass over time and simply evaporate. However, according to classical gravity theory, these celestial bodies are indestructible objects.
If everything falls into a black hole, does that mean there is a bottom? Black holes have no bottom. Celestial bodies are believed to be infinite. For black holes, the familiar concepts of “space” and “time” do not work, and the familiar laws of physics do not apply. However, some experts suspect that there are parts of the celestial body where cosmic matter is compressed into tiny dots where gravity changes.
What would happen if a human fell into a black hole? Some scientists believe that astronauts who fall into a black hole will definitely die. People can die from radiation, burn up in gas clouds in accretion disks, or be stretched vertically and horizontally by intense gravitational pressure. In 2021, a group of American astrophysicists named the conditions under which humans can cross a black hole’s event horizon relatively safely: no surrounding accretion disk and supermassive mass. However, it is impossible to conduct such an experiment. The nearest black hole is 1600 light years from Earth, it is impossible to get out of it, and it is also impossible to transmit information from it.