Black holes can safely be called one of the most mysterious objects in the universe. Probably everyone has heard about them, but few people - except for physicists, astrophysicists and other specialists - understand what they really are.
Famous astrophysicist, author and main organizer of the STARMUS festival Garik Israelyan, in an interview with Armenian News-NEWS.am correspondent, told what black holes are, how they are “born” and how many of them there are in our galaxy.
In 1999, Garik Israelyan led a scientific effort in which a group of scientists presented the first observations and evidence that the formation of black holes is caused by supernova explosions. The study was published in the journal Nature and has led to numerous scientific discoveries since.
According to Garik Israelyan, a black hole is an object that has such a strong gravity that it sucks everything around. Nothing can leave this object - it absorbs absolutely everything, even light.
In fact, a black hole is not a hole in the literal sense of the word. Most likely, it has the shape of a sphere, but it does not consist of atoms, but of neutrons.
Black holes have a huge density, and their characteristic size is believed to correspond to the Schwarzschild radius. At the same time, a black hole can "draw" into itself stars many times larger than itself, and its size will practically not change.
If we can't see black holes, how can we be sure they even exist?
As Garik Israelyan explained, although black holes themselves are not visible to us, we can see the so-called "side effects" of their existence. If there is a "normal" star near the black hole, the latter starts to rotate around the black hole very quickly. Gradually, the black hole "sucks in", absorbs the star. By cosmic standards, this happens quite quickly - in about 500,000 years.
Most objects in the universe have a limited "lifetime", but black holes could possibly exist indefinitely. As the specialist explained, it is believed that the black hole does not lose energy, and this, perhaps, ensures its eternal existence.
True, according to the theory proposed by Stephen Hawking back in the last century, black holes still have radiation. Hawking radiation is a hypothetical process of radiation by a black hole of various elementary particles, mainly photons. The fact is that a black hole can be considered an object that does not emit anything, but only absorbs matter, only until quantum effects are taken into account. Quantum mechanics fully admits that a black hole can have radiation and lose energy and mass.
If this is indeed the case, this would mean that black holes are not infinite at all - and could disappear after tens of trillions of years. However, scientists have not yet been able to detect Hawking radiation - if it exists, it is impossible to see and register it with current technologies.
In our galaxy, scientists have discovered about 30 black holes, but in fact, as Garik Israelyan noted, there are several hundred million. It's just that there are no stars next to them, and, as noted above, they themselves do not have radiation visible to us, so we do not see these holes, but we guess that they exist.
As the specialist noted, the theory of stellar evolution says that massive stars at the end of their evolution become either neutron stars or black holes. A neutron star is a cosmic body whose core consists mainly of neutrons and is covered with an approximately 1-kilometer layer of heavy atomic nuclei and electrons. Neutron stars have a huge mass, comparable to the mass of the Sun, but their radius is only about 10-20 km - and a huge density.
According to Garik Israelyan, this process is endless: sooner or later, warm stars reach the "peak" of their evolution and explode, and new black holes and neutron stars are born.