What is in the “tunnel” of a black hole, where does it lead? Where do cosmic black holes lead? What happens in black holes?

As part of a cosmic nesting doll, our universe may be located inside a black hole, which itself is part of the larger universe. All black holes discovered in our Universe - from microscopic to supermassive - may be doorways to alternate realities.

One of the latest "hallucinogenic" theories says that a black hole is a tunnel between universes - something like a wormhole. The black hole does not collapse to one point, as expected, but becomes a "white hole" at the other end of the black hole.

In a paper published in the journal Physics Letters B, Indiana University physicist Nikodem Poplavsky presented a new mathematical model for the spiraling motion of matter falling into a black hole. His equations show that such wormholes are viable alternatives to the spacetime singularities that Albert Einstein hypothesized to be at the center of black holes.

According to the equations of Einstein's general theory of relativity, singularities are created when matter in a region becomes too dense, as in the superdense heart of a black hole.

Einstein's theory suggests that singularities do not occupy space, are infinitely dense and infinitely hot - which, in principle, is supported by numerous indirect evidence, but remains difficult to understand for many scientists.

If Poplavsky is right, he may not have to understand.

According to the new equations, the matter that the black hole absorbs and apparently destroys becomes the building material for galaxies, stars and planets in another reality.

Can wormholes solve the mystery of the Big Bang?

Poplavsky says understanding black holes as wormholes could explain certain mysteries in modern cosmology. For example, the big bang theory states that the universe began with a singularity. But scientists are not satisfied with the explanation of how such a singularity could have formed in the first place. If our universe was born from a white hole rather than a singularity, “that solves the problem of black hole singularities and the big bang singularity.”

Wormholes may also explain gamma-ray bursts, the second most powerful explosions in the universe after the Big Bang. Gamma-ray bursts occur on the periphery of the known universe. They have been linked to supernovae, or star deaths, in distant galaxies, but their exact sources are a mystery. Poplavsky suggests that the bursts may be ejections of matter from alternative universes. Matter enters our universe through supermassive black holes - wormholes - at the hearts of galaxies, although it is not clear how this is possible.

“The idea is crazy, but who knows?” says the scientist.
There is at least one way to test Poplavsky's theory. Some of the black holes in our universe are spinning, and if our universe was born inside the same spinning black hole, then it should inherit the rotation of its parent object. If future experiments show that our universe rotates in the expected direction, this could be indirect evidence of the wormhole theory.

Can wormholes produce “exotic matter”?

The wormhole theory may also explain why some features of our universe deviate from what the theory predicts, according to physicists. Based on the Standard Model of physics, after the Big Bang, the curvature of the Universe should increase with time, so after 13.7 billion years, that is, today, we should be sitting on the surface of a closed spherical Universe.

However, observations show that the Universe is flat in all directions. Additionally, light data from the young Universe shows that the temperature after the big bang was roughly the same everywhere. This means that the most distant objects we see at the opposite end of the universe were close enough to each other that they were in equilibrium, like gas molecules in a sealed chamber.

Again, the observations do not match the predictions because the opposite objects in the known universe are so far apart that the time it would take to travel between them at the speed of light exceeds the age of the universe.

To explain the discrepancies, astronomers developed the inflationary theory.

Inflation suggests that shortly after the universe was created, it experienced a rapid growth spurt during which space itself expanded at faster than the speed of light. The universe stretched from the size of an atom to astronomical proportions in a fraction of a second.

The universe therefore appears flat because we are on a sphere which is extremely large from our point of view; just like the Earth appears flat to someone standing in a field.

Inflation also explains how objects that are far apart could once be close enough to interact. But even if we assume that inflation is real, astronomers struggle to explain what caused it. And this is where the new wormhole theory comes to the rescue.

According to Poplavsky, some inflationary theories say the event was caused by "exotic matter," a theoretical substance that is different from normal matter in part because it is repelled rather than attracted by gravity. Based on these equations, Poplavsky concluded that such exotic matter could have arisen when some of the first massive stars collapsed into wormholes.

"There may have been some interaction between the exotic matter that formed the wormholes and the exotic matter that caused the inflation," he says.
Wormhole equations - "a good solution"

The new model is not the first to suggest that other universes exist inside black holes. Damien Isson, a theoretical physicist at the University of Arizona, has previously suggested this.

"What's new? That the solution to wormholes in general relativity is a transition from the outside of the black hole to the inside of the new universe,” says Isson, who was not involved in Poplavsky’s research. “We simply assumed that such a solution could exist, but Poplavsky found it.”
However, the idea seems very controversial to Isson.

"Is it possible? Yes. Is such a scenario likely? Don't even know. But it’s definitely interesting.”
Future work in quantum gravity—the study of gravity at the subatomic level—will refine the equations and potentially confirm or refute Poplavsky's theory.

There is nothing surprising in the wormhole theory

Overall, the wormhole theory is interesting, but not groundbreaking, and doesn't shed any light on the origins of the universe, said Andreas Albrecht, a physicist at the University of California, Davis, who was also not involved in the study.

By asserting that our universe was created from a piece of matter from the parent universe, the theory simply shifts the event of the origin of all things into an alternative reality. In other words, it does not explain how the parent universe arose or why ours has the properties it does - moreover, the properties must be inherited, which means the parent universe will be the same.

“There are several pressing problems that we are trying to solve, and it is not clear where this will all lead,” he says, noting Poplavsky’s research.
Still, Albrecht doesn't find the idea of ​​wormholes linking universes any weirder than the idea of ​​singularities in black holes, and he's not going to dismiss the new theory just because it looks a little crazy.

"Everything people do in this industry is pretty weird," he says. - “You have no right to say that the less strange idea will win, because this will not happen, under any circumstances.”

In the acclaimed science fiction film Interstellar, the plot revolves around a colossal “black hole”. The existence of these cosmic objects truly remains one of the most intriguing mysteries of the Universe. And perhaps, having figured out how they work, humanity will gain access to worlds that they don’t even know about yet.

Death of a Star

The discovery of “black holes” is directly related to the new vision of the physical structure of the Universe, which was proposed by Albert Einstein in 1915, showing that massive bodies bend time and space. Subsequently, his theory received numerous experimental confirmations. It is not easy to explain what such a curvature looks like, so physicists resort to an analogy, imagining space as a kind of rubber surface on which metal balls press. Moreover, the more massive the ball, the larger the dent under it. In real four-dimensional space, the “dent” faces the fifth dimension, the presence of which we determine only indirectly - by the distortion of the beam or the delay of the radio signal passing near the Sun or stars.

It is clear that the “dent” created by the Sun is relatively small (its radius is only 50 kilometers larger than the radius of our star), however, almost immediately after Einstein formulated the postulates of his revolutionary theory, the German astrophysicist Karl Schwarzschild mathematically proved that somewhere then in the Universe there may be objects with a mass that bends space so much that even light cannot escape from it. Over time, such objects began to be called “black holes” with the light hand of the American John Wheeler.

For a long time, “black holes” remained a beautiful hypothesis in the eyes of scientists. In 1939, the young physicist Robert Oppenheimer, the future “father” of the American atomic bomb, showed that under certain conditions a star can turn into a real “black hole”. Indeed, astronomers soon discovered that towards the end of their “life” stars behave differently. For example, the Sun, gradually burning out, will begin to expand, and then turn into a white dwarf the size of the Earth, which will cool over billions of years, becoming a dark dense clump of matter. Those stars whose mass is much greater than the Sun burn their fuel much faster and then implode (collapse), forming a neutron star or “black hole”. Neutron stars are composed almost entirely of atomic nuclei, and "black holes" are made of curved space and curved time. Although a “black hole” does not contain matter, it has a surface - it is called an “event horizon”, through which nothing can escape.

Over time, they learned to detect “black holes” by the influence they have on the surrounding space. About a thousand such objects have been found, but astronomers say there are hundreds of millions of them. It turned out that in the centers of galaxies there are also giant “black holes”, which may have appeared as a result of the collapse of massive gas clouds.

Hawking's discovery

Many physicists have tried to understand how “black holes” work. The greatest success in this field was achieved by the Englishman Stephen Hawking. In 1975, he not only managed to connect the existence of “black holes” with fashionable quantum mechanics, but also showed how it should interact with the outside world.

Before Hawking, it was believed that a “black hole” only absorbs matter without giving anything back. Studying the behavior of quantum fields near a “black hole,” Hawking suggested that it necessarily radiates particles into outer space and thereby loses mass. This effect is now called “Hawking radiation” (or “Hawking evaporation”). Hawking calculated that such radiation would have a thermal spectrum - accordingly, it could be detected by a certain temperature. However, this temperature is so low that astronomers cannot detect it for observed “black holes,” so Hawking’s hypothesis is not confirmed by observations.

The theory of "black holes", created by Stephen Hawking, is disputed by a number of scientists. The fact is that in the classical view, a “black hole” can only grow, absorbing more and more masses of matter. It follows from this that information, as one of the characteristics of matter inside a “black hole,” is not destroyed, but is stored forever or transferred from our Universe to some other. Hawking argues that the “hole” always remains in its original state, destroying information and dumping excess mass in the form of radiation. Thus, the two models come into conflict, and the construction of a quantum gravity model depends on who is right, which directly leads to the creation of the notorious “theory of everything”, which will someday revolutionize our understanding of the Universe.

In 2004, Stephen Hawking claimed to have resolved the discrepancy between the models. His new discovery is based on the fact that in real processes of formation and evaporation of “black holes” information is not destroyed. This happens because those “holes” that are described within the framework of numerous theories simply do not exist in nature. What astronomers observe in the centers of galaxies are “apparent black holes,” that is, objects that are in many ways similar to the models invented by physicists, but do not have a real “event horizon.” Roughly speaking, according to the old theory (also called the “wall of fire concept”), an astronaut falling into a “black hole” will be instantly vaporized on the “event horizon”, and according to the new one, he will penetrate inside, but will acquire some special physical properties.

However, the new discovery also caused sharp criticism from colleagues. It turns out that Hawking took for granted a number of assumptions that themselves still need to be justified, therefore it is premature to say that the topic is completely closed.

Door to another world

Christopher Nolan's acclaimed science fiction film Interstellar clearly shows how entering a black hole and studying its internal properties will affect modern physics. In fact, we are talking about gravity control technologies and superluminal flight. Moreover, the film even shows people of the future - creatures who have mastered space with more dimensions than ours.

All these ideas were brought into the film by the famous physicist Kip Thorne (by the way, he is one of those who managed to substantiate the theoretical possibility of building a “time machine”). In 1991, he made a bet with Stephen Hawking about the existence of “naked singularities,” that is, objects that have all the properties of the center of a “black hole,” but do not have an “event horizon.” Moreover, Thorne argued that such objects could exist in reality, but Hawking considered them fantasy. And just five years later, the dispute was resolved in Thorne’s favor: Texan Matthew Choptyuk, using mathematical modeling, proved that when a gravitational wave collapses, it is possible to achieve a state where something like boiling space and time arises. It generates new gravitational waves until eventually an infinitesimal “naked singularity” is formed.

Kip Thorne clarifies that there are no “naked singularities” in nature: the laws of physics prohibit their spontaneous occurrence. However, some powerful civilization that has studied “black holes” and managed to construct a technology for generating gravitational waves may well create an artificial “naked singularity.” And then such a civilization will not only have the opportunity to travel through our Universe faster than the speed of light, but will also penetrate into other universes. Perhaps, Thorne further reports, such a civilization is already operating in our space, watching us and is ready to intervene if something goes wrong with us. His idea sounds like a fantasy, but who can know for sure?..

Anton Pervushin

Can wormholes produce “exotic matter”?

The wormhole theory may also explain why some features of our universe deviate from what the theory predicts, according to physicists. Based on the Standard Model of physics, after the Big Bang, the curvature of the Universe should increase with time, so after 13.7 billion years, that is, today, we should be sitting on the surface of a closed spherical Universe.

However, observations show that the Universe is flat in all directions. Additionally, light data from the young Universe shows that the temperature after the big bang was roughly the same everywhere. This means that the most distant objects we see at the opposite end of the universe were close enough to each other that they were in equilibrium, like gas molecules in a sealed chamber.

Again, the observations do not match the predictions because the opposite objects in the known universe are so far apart that the time it would take to travel between them at the speed of light exceeds the age of the universe.

To explain the discrepancies, astronomers developed the inflationary theory.

Inflation suggests that shortly after the universe was created, it experienced a rapid growth spurt during which space itself expanded at faster than the speed of light. The universe stretched from the size of an atom to astronomical proportions in a fraction of a second.

The universe therefore appears flat because we are on a sphere which is extremely large from our point of view; just like the Earth appears flat to someone standing in a field.

Inflation also explains how objects that are far apart could once be close enough to interact. But even if we assume that inflation is real, astronomers struggle to explain what caused it. And this is where the new wormhole theory comes to the rescue.

According to Poplavsky, some inflationary theories say the event was caused by "exotic matter," a theoretical substance that is different from normal matter in part because it is repelled rather than attracted by gravity. Based on these equations, Poplavsky concluded that such exotic matter could have arisen when some of the first massive stars collapsed into wormholes.

"There may have been some interaction between the exotic matter that formed the wormholes and the exotic matter that caused the inflation," he says.

Wormhole equations - "a good solution"

The new model is not the first to suggest that other universes exist inside black holes. Damien Isson, a theoretical physicist at the University of Arizona, has previously suggested this.

"What's new? That the solution to wormholes in general relativity is a transition from the outside of the black hole to the inside of the new universe,” says Isson, who was not involved in Poplavsky’s research. “We simply assumed that such a solution could exist, but Poplavsky found it.”

However, the idea seems very controversial to Isson.

"Is it possible? Yes. Is such a scenario likely? Don't even know. But it’s definitely interesting.”

Future work in quantum gravity—the study of gravity at the subatomic level—will refine the equations and potentially confirm or refute Poplavsky's theory.

There is nothing surprising in the wormhole theory

Overall, the wormhole theory is interesting, but not groundbreaking, and doesn't shed any light on the origins of the universe, said Andreas Albrecht, a physicist at the University of California, Davis, who was also not involved in the study.

By asserting that our universe was created from a piece of matter from the parent universe, the theory simply shifts the event of the origin of all things into an alternative reality. In other words, it does not explain how the parent universe arose or why ours has the properties it does - moreover, the properties must be inherited, which means the parent universe will be the same.

“There are several pressing problems that we are trying to solve, and it is not clear where this will all lead,” he says, noting Poplavsky’s research.

Still, Albrecht doesn't find the universe-connecting idea any stranger than the idea of ​​singularities in black holes, and he's not going to throw out a new theory just because it looks a little crazy.

"Everything people do in this industry is pretty weird," he says. - “You have no right to say that the less strange idea will win, because this will not happen, under any circumstances.”

Due to the relatively recent growth of interest in creating popular science films on the topic of space exploration, modern viewers have heard a lot about phenomena such as the singularity, or a black hole. However, movies obviously do not reveal the full nature of these phenomena, and sometimes even distort the constructed scientific theories for greater effect. For this reason, the understanding of many modern people about these phenomena is either completely superficial or completely erroneous. One of the solutions to the problem that has arisen is this article, in which we will try to understand the existing research results and answer the question - what is a black hole?

In 1784, the English priest and naturalist John Michell first mentioned in a letter to the Royal Society a certain hypothetical massive body that has such a strong gravitational attraction that its second escape velocity will exceed the speed of light. The second escape velocity is the speed that a relatively small object will need to overcome the gravitational attraction of a celestial body and go beyond the closed orbit around this body. According to his calculations, a body with the density of the Sun and a radius of 500 solar radii will have a second cosmic velocity on its surface equal to the speed of light. In this case, even light will not leave the surface of such a body, and therefore this body will only absorb the incoming light and will remain invisible to the observer - a kind of black spot against the background of dark space.

However, Michell's concept of a supermassive body did not attract much interest until the work of Einstein. Let us recall that the latter defined the speed of light as the maximum speed of information transfer. In addition, Einstein expanded the theory of gravity to speeds close to the speed of light (). As a result, it was no longer relevant to apply Newtonian theory to black holes.

Einstein's equation

As a result of applying general relativity to black holes and solving Einstein's equations, the main parameters of a black hole were identified, of which there are only three: mass, electric charge and angular momentum. It is worth noting the significant contribution of the Indian astrophysicist Subramanian Chandrasekhar, who created the fundamental monograph: “Mathematical Theory of Black Holes.”

Thus, the solution to Einstein’s equations is presented in four options for four possible types of black holes:

• BH without rotation and without charge – Schwarzschild solution. One of the first descriptions of a black hole (1916) using Einstein’s equations, but without taking into account two of the three parameters of the body. The solution of the German physicist Karl Schwarzschild allows one to calculate the external gravitational field of a spherical massive body. The peculiarity of the concept of black holes of the German scientist is the presence of an event horizon and hiding behind it. Schwarzschild was also the first to calculate the gravitational radius, which received his name, which determines the radius of the sphere on which the event horizon would be located for a body with a given mass.
• BH without rotation with charge – Reisner-Nordström solution. A solution put forward in 1916-1918, taking into account the possible electric charge of a black hole. This charge cannot be arbitrarily large and is limited due to the resulting electrical repulsion. The latter must be compensated by gravitational attraction.
• BH with rotation and without charge - Kerr's solution (1963). A rotating Kerr black hole differs from a static one by the presence of a so-called ergosphere (read more about this and other components of a black hole).
• BH with rotation and charge - Kerr-Newman solution. This solution was calculated in 1965 and is currently the most complete, since it takes into account all three parameters of the black hole. However, it is still assumed that in nature black holes have an insignificant charge.

Black hole formation

There are several theories about how a black hole forms and appears, the most famous of which is that it arises as a result of the gravitational collapse of a star with sufficient mass. Such compression can end the evolution of stars with a mass of more than three solar masses. Upon completion of thermonuclear reactions inside such stars, they begin to rapidly compress into super-dense stars. If the gas pressure of a neutron star cannot compensate for gravitational forces, that is, the mass of the star overcomes the so-called. Oppenheimer-Volkoff limit, then the collapse continues, resulting in matter being compressed into a black hole.

The second scenario describing the birth of a black hole is the compression of protogalactic gas, that is, interstellar gas at the stage of transformation into a galaxy or some kind of cluster. If there is insufficient internal pressure to compensate for the same gravitational forces, a black hole may arise.

Two other scenarios remain hypothetical:

• The occurrence of a black hole as a result of the so-called primordial black holes.
• Occurrence as a result of nuclear reactions occurring at high energies. An example of such reactions is experiments at colliders.

Structure and physics of black holes

The structure of a black hole according to Schwarzschild includes only two elements that were mentioned earlier: the singularity and the event horizon of the black hole. Briefly speaking about the singularity, it can be noted that it is impossible to draw a straight line through it, and also that most existing physical theories do not work inside it. Thus, the physics of the singularity remains a mystery to scientists today. a black hole is a certain boundary, crossing which a physical object loses the opportunity to return back beyond its limits and will definitely “fall” into the singularity of the black hole.

The structure of a black hole becomes somewhat more complicated in the case of the Kerr solution, namely in the presence of rotation of the black hole. Kerr's solution assumes that the hole has an ergosphere. The ergosphere is a certain region located outside the event horizon, inside which all bodies move in the direction of rotation of the black hole. This area is not yet exciting and it is possible to leave it, unlike the event horizon. The ergosphere is probably some kind of analogue of an accretion disk, representing rotating matter around massive bodies. If a static Schwarzschild black hole is represented as a black sphere, then the Kerry black hole, due to the presence of an ergosphere, has the shape of an oblate ellipsoid, in the form of which we often saw black holes in drawings, in old movies or video games.

• How much does a black hole weigh? – The most theoretical material on the emergence of a black hole is available for the scenario of its appearance as a result of the collapse of a star. In this case, the maximum mass of a neutron star and the minimum mass of a black hole are determined by the Oppenheimer - Volkov limit, according to which the lower limit of the mass of a black hole is 2.5 - 3 solar masses. The heaviest black hole that has been discovered (in the galaxy NGC 4889) has a mass of 21 billion solar masses. However, we should not forget about black holes that hypothetically arise as a result of nuclear reactions at high energies, such as those at colliders. The mass of such quantum black holes, in other words “Planck black holes,” is of the order of magnitude, namely 2·10−5 g.
• Black hole size. The minimum radius of a black hole can be calculated from the minimum mass (2.5 – 3 solar masses). If the gravitational radius of the Sun, that is, the area where the event horizon would be located, is about 2.95 km, then the minimum radius of a black hole of 3 solar masses will be about nine kilometers. Such relatively small sizes do not fit into the mind when we are talking about massive objects that attract everything around them. However, for quantum black holes the radius is 10 −35 m.
• The average density of a black hole depends on two parameters: mass and radius. The density of a black hole with a mass of about three solar masses is about 6 10 26 kg/m³, while the density of water is 1000 kg/m³. However, such small black holes have not been found by scientists. Most detected black holes have a mass greater than 10 5 solar masses. There is an interesting pattern according to which the more massive the black hole, the lower its density. In this case, a change in mass by 11 orders of magnitude entails a change in density by 22 orders of magnitude. Thus, a black hole with a mass of 1·10 9 solar masses has a density of 18.5 kg/m³, which is one less than the density of gold. And black holes with a mass of more than 10 10 solar masses can have an average density less than that of air. Based on these calculations, it is logical to assume that the formation of a black hole does not occur due to compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume. In the case of quantum black holes, their density can be about 10 94 kg/m³.
• The temperature of a black hole also depends inversely on its mass. This temperature is directly related to. The spectrum of this radiation coincides with the spectrum of an absolutely black body, that is, a body that absorbs all incident radiation. The radiation spectrum of an absolutely black body depends only on its temperature, then the temperature of the black hole can be determined from the Hawking radiation spectrum. As mentioned above, this radiation is more powerful the smaller the black hole. At the same time, Hawking radiation remains hypothetical, since it has not yet been observed by astronomers. It follows from this that if Hawking radiation exists, then the temperature of the observed black holes is so low that it does not allow this radiation to be detected. According to calculations, even the temperature of a hole with a mass on the order of the mass of the Sun is negligibly small (1·10 -7 K or -272°C). The temperature of quantum black holes can reach about 10 12 K, and with their rapid evaporation (about 1.5 minutes), such black holes can emit the energy of about ten million atomic bombs. But, fortunately, to create such hypothetical objects would require energy 10 14 times greater than that achieved today at the Large Hadron Collider. In addition, such phenomena have never been observed by astronomers.

What does a black hole consist of?

Another question worries both scientists and those who are simply interested in astrophysics - what does a black hole consist of? There is no clear answer to this question, since it is not possible to look beyond the event horizon surrounding any black hole. In addition, as mentioned earlier, theoretical models of a black hole provide for only 3 of its components: the ergosphere, the event horizon and the singularity. It is logical to assume that in the ergosphere there are only those objects that were attracted by the black hole and that now revolve around it - various kinds of cosmic bodies and cosmic gas. The event horizon is just a thin implicit boundary, once beyond which the same cosmic bodies are irrevocably attracted towards the last main component of the black hole - the singularity. The nature of the singularity has not been studied today and it is too early to talk about its composition.

According to some assumptions, a black hole may consist of neutrons. If we follow the scenario of the occurrence of a black hole as a result of the compression of a star to a neutron star with its subsequent compression, then probably the main part of the black hole consists of neutrons, of which the neutron star itself consists. In simple terms: when a star collapses, its atoms are compressed in such a way that electrons combine with protons, thereby forming neutrons. A similar reaction actually occurs in nature, and with the formation of a neutron, neutrino radiation occurs. However, these are just assumptions.

What happens if you fall into a black hole?

Falling into an astrophysical black hole causes the body to stretch. Consider a hypothetical suicide cosmonaut who heads into a black hole wearing only a spacesuit, feet first. Crossing the event horizon, the astronaut will not notice any changes, despite the fact that he no longer has the opportunity to get back. At some point, the astronaut will reach a point (slightly behind the event horizon) at which deformation of his body will begin to occur. Since the gravitational field of a black hole is non-uniform and is represented by a force gradient increasing towards the center, the astronaut’s legs will be subject to a noticeably greater gravitational influence than, for example, the head. Then, due to gravity, or rather tidal forces, the legs will “fall” faster. Thus, the body begins to gradually elongate in length. To describe this phenomenon, astrophysicists have come up with a rather creative term - spaghettification. Further stretching of the body will probably decompose it into atoms, which, sooner or later, will reach a singularity. One can only guess how a person will feel in this situation. It is worth noting that the effect of stretching a body is inversely proportional to the mass of the black hole. That is, if a black hole with the mass of three Suns instantly stretches/tears the body, then the supermassive black hole will have lower tidal forces and there are suggestions that some physical materials could “tolerate” such deformation without losing their structure.

As you know, time flows slower near massive objects, which means time for a suicide bomber astronaut will flow much slower than for earthlings. In this case, perhaps he will outlive not only his friends, but also the Earth itself. To determine how much time will slow down for an astronaut, calculations will be required, but from the above it can be assumed that the astronaut will fall into the black hole very slowly and, perhaps, simply will not live to see the moment when his body begins to deform.

It is noteworthy that for an observer from the outside, all bodies that fly up to the event horizon will remain at the edge of this horizon until their image disappears. The reason for this phenomenon is gravitational redshift. Simplifying somewhat, we can say that the light falling on the body of a suicide cosmonaut “frozen” at the event horizon will change its frequency due to its slowed down time. As time passes more slowly, the frequency of light will decrease and the wavelength will increase. As a result of this phenomenon, at the output, that is, for an external observer, the light will gradually shift towards low frequency - red. A shift of light along the spectrum will take place, as the suicide cosmonaut moves further and further away from the observer, although almost imperceptibly, and his time flows more and more slowly. Thus, the light reflected by his body will soon go beyond the visible spectrum (the image will disappear), and in the future the astronaut’s body can be detected only in the region of infrared radiation, later in radio frequency, and as a result the radiation will be completely elusive.

Despite the above, it is assumed that in very large supermassive black holes, tidal forces do not change so much with distance and act almost uniformly on the falling body. In this case, the falling spacecraft would retain its structure. A reasonable question arises: where does the black hole lead? This question can be answered by the work of some scientists, linking two phenomena such as wormholes and black holes.

Back in 1935, Albert Einstein and Nathan Rosen put forward a hypothesis about the existence of so-called wormholes, connecting two points of space-time through places of significant curvature of the latter - an Einstein-Rosen bridge or wormhole. For such a powerful curvature of space, bodies with gigantic mass would be required, the role of which would be perfectly fulfilled by black holes.

The Einstein-Rosen Bridge is considered an impassable wormhole because it is small in size and unstable.

A traversable wormhole is possible within the framework of the theory of black and white holes. Where the white hole is the output of information trapped in the black hole. The white hole is described within the framework of general relativity, but today remains hypothetical and has not been discovered. Another model of a wormhole was proposed by American scientists Kip Thorne and his graduate student Mike Morris, which can be passable. However, both in the case of the Morris-Thorne wormhole and in the case of black and white holes, the possibility of travel requires the existence of so-called exotic matter, which has negative energy and also remains hypothetical.

Black holes in the Universe

The existence of black holes was confirmed relatively recently (September 2015), but before that time there was already a lot of theoretical material on the nature of black holes, as well as many candidate objects for the role of a black hole. First of all, you should take into account the size of the black hole, since the very nature of the phenomenon depends on them:

• Stellar mass black hole. Such objects are formed as a result of the collapse of a star. As mentioned earlier, the minimum mass of a body capable of forming such a black hole is 2.5 - 3 solar masses.
• Intermediate mass black holes. A conditional intermediate type of black hole that has grown due to the absorption of nearby objects, such as a cluster of gas, a neighboring star (in systems of two stars) and other cosmic bodies.
• Supermassive black hole. Compact objects with 10 5 -10 10 solar masses. The distinctive properties of such black holes are their paradoxically low density, as well as weak tidal forces, which were mentioned earlier. This is exactly the supermassive black hole at the center of our Milky Way galaxy (Sagittarius A*, Sgr A*), as well as most other galaxies.

Candidates for the ChD

The nearest black hole, or rather a candidate for the role of a black hole, is an object (V616 Monoceros), which is located at a distance of 3000 light years from the Sun (in our galaxy). It consists of two components: a star with a mass of half the mass of the Sun, as well as an invisible small body whose mass is 3–5 solar masses. If this object turns out to be a small black hole of stellar mass, then it will rightfully become the nearest black hole.

Following this object, the second closest black hole is the object Cygnus X-1 (Cyg X-1), which was the first candidate for the role of a black hole. The distance to it is approximately 6070 light years. Quite well studied: it has a mass of 14.8 solar masses and an event horizon radius of about 26 km.

According to some sources, another closest candidate for the role of a black hole may be a body in the star system V4641 Sagittarii (V4641 Sgr), which, according to estimates in 1999, was located at a distance of 1600 light years. However, subsequent studies have increased this distance by at least 15 times.

How many black holes are there in our galaxy?

There is no exact answer to this question, since observing them is quite difficult, and over the entire period of studying the sky, scientists have been able to discover about a dozen black holes within the Milky Way. Without indulging in calculations, we note that there are about 100–400 billion stars in our galaxy, and approximately every thousandth star has enough mass to form a black hole. It is likely that millions of black holes could have formed during the existence of the Milky Way. Since it is easier to detect black holes of enormous size, it is logical to assume that most likely the majority of black holes in our galaxy are not supermassive. It is noteworthy that NASA research in 2005 suggests the presence of a whole swarm of black holes (10-20 thousand) revolving around the center of the galaxy. In addition, in 2016, Japanese astrophysicists discovered a massive satellite near the object * - a black hole, the core of the Milky Way. Due to the small radius (0.15 light years) of this body, as well as its enormous mass (100,000 solar masses), scientists assume that this object is also a supermassive black hole.

The core of our galaxy, the black hole of the Milky Way (Sagittarius A*, Sgr A* or Sagittarius A*) is supermassive and has a mass of 4.31 10 6 solar masses, and a radius of 0.00071 light years (6.25 light hours . or 6.75 billion km). The temperature of Sagittarius A*, together with the cluster around it, is about 1·10 7 K.

The largest black hole

The largest black hole in the Universe that scientists have discovered is a supermassive black hole, FSRQ blazar, in the center of the galaxy S5 0014+81, at a distance of 1.2 10 10 light years from Earth. According to preliminary observation results using the Swift space observatory, the mass of the black hole was 40 billion (40·10 9) solar masses, and the Schwarzschild radius of such a hole was 118.35 billion kilometers (0.013 light years). In addition, according to calculations, it arose 12.1 billion years ago (1.6 billion years after the Big Bang). If this giant black hole does not absorb the matter surrounding it, it will live to the era of black holes - one of the eras of the development of the Universe, during which black holes will dominate in it. If the core of the galaxy S5 0014+81 continues to grow, it will become one of the last black holes that will exist in the Universe.

The other two known black holes, although they do not have their own names, are of greatest importance for the study of black holes, since they confirmed their existence experimentally, and also provided important results for the study of gravity. We are talking about the event GW150914, which is the collision of two black holes into one. This event made it possible to register.

Detection of black holes

Before considering methods for detecting black holes, we should answer the question - why is a black hole black? – the answer to this does not require deep knowledge of astrophysics and cosmology. The fact is that a black hole absorbs all the radiation falling on it and does not emit at all, if you do not take into account the hypothetical one. If we consider this phenomenon in more detail, we can assume that processes leading to the release of energy in the form of electromagnetic radiation do not occur inside black holes. Then, if a black hole emits, it does so in the Hawking spectrum (which coincides with the spectrum of a heated, absolutely black body). However, as mentioned earlier, this radiation was not detected, which suggests that the temperature of black holes is completely low.

Another generally accepted theory says that electromagnetic radiation is not at all capable of leaving the event horizon. It is most likely that photons (particles of light) are not attracted by massive objects, since, according to the theory, they themselves have no mass. However, the black hole still “attracts” photons of light through the distortion of space-time. If we imagine a black hole in space as a kind of depression on the smooth surface of space-time, then there is a certain distance from the center of the black hole, approaching which light will no longer be able to move away from it. That is, roughly speaking, the light begins to “fall” into a “hole” that does not even have a “bottom”.

In addition, if we take into account the effect of gravitational redshift, it is possible that light in a black hole loses its frequency, shifting along the spectrum into the region of low-frequency long-wave radiation until it loses energy altogether.

So, a black hole is black in color and therefore difficult to detect in space.

Detection methods

Let's look at the methods that astronomers use to detect a black hole:

In addition to the methods mentioned above, scientists often associate objects such as black holes and. Quasars are certain clusters of cosmic bodies and gas, which are among the brightest astronomical objects in the Universe. Since they have a high luminescence intensity at relatively small sizes, there is reason to assume that the center of these objects is a supermassive black hole, attracting surrounding matter. Due to such a powerful gravitational attraction, the attracted matter is so heated that it radiates intensely. The discovery of such objects is usually compared with the discovery of a black hole. Sometimes quasars can emit jets of heated plasma in two directions - relativistic jets. The reasons for the appearance of such jets are not entirely clear, but they are probably caused by the interaction of the magnetic fields of the black hole and the accretion disk, and are not emitted by the direct black hole.

Jet in the M87 galaxy shooting from the center of the black hole

To summarize the above, you can imagine, close up: this is a spherical black object around which highly heated matter rotates, forming a luminous accretion disk.

Mergers and collisions of black holes

One of the most interesting phenomena in astrophysics is the collision of black holes, which also makes it possible to detect such massive astronomical bodies. Such processes are of interest not only to astrophysicists, since they result in phenomena poorly studied by physicists. The most striking example is the previously mentioned event called GW150914, when two black holes came so close that, as a result of their mutual gravitational attraction, they merged into one. An important consequence of this collision was the emergence of gravitational waves.

According to the definition, gravitational waves are changes in the gravitational field that propagate in a wave-like manner from massive moving objects. When two such objects come closer, they begin to rotate around a common center of gravity. As they get closer, their rotation around their own axis increases. Such alternating oscillations of the gravitational field at some moment can form one powerful gravitational wave, which can spread through space for millions of light years. Thus, at a distance of 1.3 billion light years, two black holes collided, generating a powerful gravitational wave that reached the Earth on September 14, 2015 and was recorded by the LIGO and VIRGO detectors.

How do black holes die?

Obviously, for a black hole to cease to exist, it would need to lose all of its mass. However, according to its definition, nothing can leave the black hole if it has crossed its event horizon. It is known that the possibility of emission of particles from a black hole was first mentioned by the Soviet theoretical physicist Vladimir Gribov, in his discussion with another Soviet scientist Yakov Zeldovich. He argued that from the point of view of quantum mechanics, a black hole is capable of emitting particles through the tunneling effect. Later, using quantum mechanics, the English theoretical physicist Stephen Hawking built his own, slightly different theory. You can read more about this phenomenon. Briefly speaking, in a vacuum there are so-called virtual particles, which are constantly born in pairs and annihilate each other, without interacting with the outside world. But if such pairs appear on the event horizon of a black hole, then strong gravity is hypothetically capable of separating them, with one particle falling into the black hole and the other moving away from the black hole. And since a particle flying away from a hole can be observed, and therefore has positive energy, then a particle falling into a hole must have negative energy. Thus, the black hole will lose its energy and an effect will occur, which is called black hole evaporation.

According to existing models of a black hole, as mentioned earlier, as its mass decreases, its radiation becomes more intense. Then, at the final stage of the black hole's existence, when it may shrink to the size of a quantum black hole, it will release a huge amount of energy in the form of radiation, which could be equivalent to thousands or even millions of atomic bombs. This event is somewhat reminiscent of the explosion of a black hole, like the same bomb. According to calculations, primordial black holes could have been born as a result of the Big Bang, and those of them with a mass of about 10 12 kg would have evaporated and exploded around our time. Be that as it may, such explosions have never been noticed by astronomers.

Despite Hawking's proposed mechanism for destroying black holes, the properties of Hawking's radiation cause a paradox within the framework of quantum mechanics. If a black hole absorbs a certain body, and then loses the mass resulting from the absorption of this body, then regardless of the nature of the body, the black hole will not differ from what it was before absorbing the body. In this case, information about the body is forever lost. From the point of view of theoretical calculations, the transformation of the initial pure state into the resulting mixed (“thermal”) state does not correspond to the current theory of quantum mechanics. This paradox is sometimes called the disappearance of information in a black hole. A definitive solution to this paradox has never been found. Known solutions to the paradox:

• The invalidity of Hawking's theory. This entails the impossibility of destroying a black hole and its constant growth.
• Presence of white holes. In this case, the absorbed information does not disappear, but is simply thrown out into another Universe.
• The inconsistency of the generally accepted theory of quantum mechanics.

Unsolved problem of black hole physics

Judging by everything that was described earlier, black holes, although they have been studied for a relatively long time, still have many features, the mechanisms of which are still unknown to scientists.

• In 1970, an English scientist formulated the so-called. “the principle of cosmic censorship” - “Nature abhors naked singularity.” This means that singularities form only in hidden places, like the center of a black hole. However, this principle has not yet been proven. There are also theoretical calculations according to which a “naked” singularity can arise.
• The “no hair theorem”, according to which black holes have only three parameters, has not been proven either.
• A complete theory of the black hole magnetosphere has not been developed.
• The nature and physics of the gravitational singularity have not been studied.
• It is not known for certain what happens at the final stage of the existence of a black hole, and what remains after its quantum decay.

Interesting facts about black holes

Summarizing the above, we can highlight several interesting and unusual features of the nature of black holes:

• BHs have only three parameters: mass, electric charge and angular momentum. As a result of such a small number of characteristics of this body, the theorem stating this is called the “no-hair theorem”. This is also where the phrase “a black hole has no hair” came from, which means that two black holes are absolutely identical, their three parameters mentioned are the same.
• The density of the black hole can be less than the density of air, and the temperature is close to absolute zero. From this we can assume that the formation of a black hole does not occur due to compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume.
• Time passes much slower for bodies absorbed by a black hole than for an external observer. In addition, the absorbed bodies stretch significantly inside the black hole, which scientists have called spaghettification.
• There may be about a million black holes in our galaxy.
• There is probably a supermassive black hole at the center of every galaxy.
• In the future, according to the theoretical model, the Universe will reach the so-called era of black holes, when black holes will become the dominant bodies in the Universe.

As part of a cosmic nesting doll, our universe may be located inside a black hole, which itself is part of the larger universe. All black holes discovered in our universe - from microscopic to supermassive - may be doorways to alternate realities.

One of the latest "Hallucinogenic" theories says that a black hole is a tunnel between universes - something like a wormhole. The black hole does not collapse to one point, as expected, but becomes a "White Hole" at the other end of the black hole.

In a paper published in the journal Physics Letters B, Indiana University physicist Nikodem Poplavsky presented a new mathematical model for the spiraling motion of matter falling into a black hole. His equations show that such wormholes are viable alternatives to the spacetime singularities that Albert Einstein hypothesized to be at the center of black holes.

According to the equations of Einstein's general theory of relativity, singularities are created when matter in a region becomes too dense, as in the superdense heart of a black hole.

Einstein's theory suggests that singularities do not occupy space, are infinitely dense and infinitely hot - which, in principle, is supported by numerous indirect evidence, but remains difficult to understand for many scientists.

If Poplavsky is right, there may be no need to understand.

According to the new equations, the matter that the black hole absorbs and apparently destroys becomes the building material for galaxies, stars and planets in another reality.

Can wormholes solve the mystery of the big bang?

Poplavsky says understanding black holes as wormholes could explain certain mysteries in modern cosmology. For example, the big bang theory states that the universe began with a singularity. But scientists are not satisfied with the explanation of how such a singularity could have formed in the first place. Thus, if our universe was born from a white hole rather than from a singularity, "this Solves the Problem of Black Hole Singularities and the Big Bang Singularity."

Wormholes may also explain gamma-ray bursts, the second most powerful explosions in the universe after the Big Bang. Gamma-ray bursts occur on the periphery of the known universe. They have been linked to supernovae, or star deaths, in distant galaxies, but their exact sources are a mystery. Poplavsky suggests that the bursts may be ejections of matter from alternative universes. Matter enters our universe through supermassive black holes - wormholes - at the hearts of galaxies, although it is not clear how this is possible.

“The idea is crazy, but who knows?” says the scientist.

There is at least one way to test Poplavsky's theory. Some of the black holes in our universe are spinning, and if our universe was born inside the same spinning black hole, then it should inherit the rotation of its parent object. Thus, if future experiments show that our universe rotates in the expected direction, this could be indirect evidence of the wormhole theory.

Can wormholes produce "Exotic Matter"?

The wormhole theory may also explain why some features of our universe deviate from what the theory predicts, according to physicists. Based on the standard model of physics, after the big bang, the curvature of the universe should increase with time, so after 13.7 billion years, which is today, we should be sitting on the surface of a closed spherical universe.

However, observations show that the universe is flat in all directions. Moreover, light data from the young universe shows that the temperature after the big bang was roughly the same everywhere. This means that the most distant objects we see at the opposite end of the universe were close enough to each other that they were in equilibrium, like gas molecules in a sealed chamber.

Again, the observations do not match the predictions because the opposite objects in the known universe are so far apart that the time it would take to travel between them at the speed of light exceeds the age of the universe.

To explain the discrepancies, astronomers developed the inflationary theory.

Inflation suggests that shortly after the universe was created, it experienced a rapid growth spurt during which space itself expanded at faster than the speed of light. The universe stretched from the size of an atom to astronomical proportions in a fraction of a second.

The universe therefore appears flat because we are on a sphere which is extremely large from our point of view; so the earth seems flat to someone who stands in a field.

Inflation also explains how objects that are far apart could once be close enough to interact. But even if we assume that inflation is real, astronomers struggle to explain what caused it. And this is where a new theory of wormholes comes to the rescue.

According to Poplavsky, some inflationary theories say the event was caused by "Exotic Matter", a theoretical substance that is different from normal matter in part because it is repelled rather than attracted by gravity. Based on these equations, Poplavsky concluded that such exotic matter could have arisen when some of the first massive stars collapsed into wormholes.

"There may have been some interaction between the Exotic Matter That Formed the Wormholes and the Exotic Matter That Caused Inflation," he says.

Wormhole Equations - "Good Solution".

The new model is not the first to suggest that other universes exist inside black holes. Damien Isson, a theoretical physicist at the University of Arizona, had previously suggested this.

"What's new? The fact that the solution of wormholes in the oto is a transition from the outside of the black hole to the inside of the new universe," says Isson, who did not take part in Poplavsky's research. - “We Just Assumed that Such a Solution Could Exist, but Poplavsky Found It.”

However, the idea seems very controversial to Isson.

“Is this possible? Yes. Is such a scenario probable? I don’t even know. But it’s definitely interesting.”

Future work in quantum gravity—the study of gravity at the subatomic level—will refine the equations and potentially confirm or refute Poplavsky's theory.

There is nothing surprising about the wormhole theory.

Overall, the wormhole theory is interesting, but not groundbreaking, and does not shed any light on the origins of the universe, said Andreas Albrecht, a physicist at the University of California, Davis, who was also not involved in the study.

By asserting that our universe was created from a piece of matter from the parent universe, the theory simply shifts the event of the origin of all things into an alternative reality. In other words, it does not explain how the parent universe arose or why ours has the properties it does - moreover, the properties must be inherited, which means the parent universe will be the same.

“There are Several Current Problems We're Trying to Solve, and It's Not Clear Where This Will Lead,” he says, noting Poplavsky's research.

However, Albrecht doesn't find the idea of ​​wormholes linking universes any "weirder" than the idea of ​​singularities in black holes, and he's not going to throw out a new theory just because it looks a little crazy.

"Everything People Do in This Sphere Is Quite Strange," he says. - “You have no right to say that the Less Strange Idea will win, because it will not Happen, under any Circumstances.” Source: hi-News.

Not so long ago (by scientific standards) an object called a black hole was purely hypothetical and was described only by superficial theoretical calculations. But the progress of technology does not stand still, and now no one doubts the existence of black holes. A lot has been written about black holes, but their descriptions are often extremely difficult for the average observer to understand. In this article we will try to understand this very interesting object.
A black hole usually forms due to the death of a neutron star. Neutron stars are usually very massive, bright and extremely hot, compared to our Sun, they are like a flashlight bulb and a giant spotlight with a bunch of megawatts that are used when filming movies. Neutron stars are extremely inefficient; they use huge reserves of nuclear fuel in relatively short periods of time, essentially like a small car or some kind of Gelik, if again compared with our star. By burning nuclear fuel, new elements are formed in the core, heavier ones, you can look at the periodic table, hydrogen turns into helium, helium into lithium, etc. Nuclear fusion fission products are similar to exhaust smoke, except that they can be reused. And just like that, the star gains momentum until it comes to iron. Iron accumulation in the core is like cancer... It begins to kill her from the inside. Because of the iron, the mass of the core grows rapidly and eventually the force of gravity becomes greater than the forces of nuclear interactions and the core literally falls, which leads to an explosion. At the moment of such an explosion, a colossal amount of energy is released, and two directed beams of gamma radiation appear, as if a laser gun is shooting into the universe from both ends, and everything that is in the path of such beams at a distance of about 10 light years is penetrated by this radiation. Naturally, nothing living survives from such rays, and anything close to it completely burns out. This radiation is considered the most powerful in the entire universe, except that the energy of the big bang has more energy. But not everything is so bad, everything that was in the core is emitted into space and is subsequently used to create planets, stars, etc. The pressure from the force of the explosion compresses the star to a tiny size; given its former size, the density becomes incredibly enormous. A hamburger crumb made from this substance would weigh more than our planet. The result is a black hole, which has incredible gravity and is called black because even light cannot escape from it.
The laws of physics near a black hole no longer work in the way we are used to. Space-time is curved and all events proceed completely differently. Like a vacuum cleaner, a black hole absorbs everything that is around it: planets, asteroids, light, etc. Previously, it was believed that a black hole does not emit anything, but as Stephen Hawking proved, a black hole emits antimatter. That is, it eats matter and releases antimatter. By the way, if you combine matter and antimatter, you get a bomb that will release energy E=mc2, well, the most powerful weapon on the planet. I believe the collider was then built to try to achieve this, since when protons collide inside this machine, miniature black holes also appear that quickly evaporate, which is good for us, otherwise it could be like in films about the end of the world.
Previously, they thought that if you throw a person into a black hole, then his pipe will tear into subatoms, but as it turned out, according to some equations, there are certain trajectories of travel through a black hole in order to feel normal, although it is not clear what will happen behind it, another peace or nothing. The region around the black hole that is interesting is called the event horizon. If you fly there without knowing the magic equation, it will certainly not be very good. The observer will see how the spacecraft flies into the event horizon and then moves away very slowly until it freezes in the center. For the astronaut himself, things will go extremely differently; the curved space will sculpt various forms out of him, like plasticine, until he finally tears everything into subatoms. But to an outside observer, the astronaut will forever remain smiling and waving out the window, a frozen image.

black hole - explanation for children: description with photos, how to find them in the cosmos of the Universe, how they appear, the death of stars, supermassive black holes of galaxies.

For the little ones, parents or at school should explain that perceiving a black hole as an empty space is a grave mistake. On the contrary, an incredible amount of matter is concentrated in it, which is confined in a small space. To make the explanation more colorful for kids, just imagine that you took a star 10 times more massive than the Sun and tried to squeeze it into an area the size of New York City. Due to this pressure, the gravitational field becomes so strong that no one, not even a light beam, can escape. With the development of technology, NASA is able to learn more and more about these mysterious objects.

A good place to start explaining for kids is that the term “black hole” didn’t exist until 1967 (coined by John Wheeler). But before this, for several centuries it was mentioned about the existence of strange objects that, due to their density and massiveness, do not release light. They were even predicted by Albert Einstein in his general theory of relativity. She proved that when a massive star dies, a small dense core remains. If a star is three times the mass of the sun, then gravity overcomes other forces, and we get a black hole.

Black star formation process

Of course, it is important to explain to children that researchers are unable to observe these features directly (telescopes only detect light, X-rays and other forms of electromagnetic radiation), so there is no need to wait for a photo of a black hole. But it is possible to calculate their location and even determine their size due to the influence they have on surrounding objects. For example, if it passes through a cloud of interstellar matter, then in the process it will begin to draw matter inward - accretion. The same thing will happen if a star passes nearby. True, a star can explode.

At the moment of attraction, the substance heats up and accelerates, releasing x-rays into space. Recent discoveries have spotted several powerful bursts of gamma rays, demonstrating the hole's devouring of nearby stars. At this moment, they stimulate the growth of some and stop others.

The death of a star is the beginning of a black hole

Most black holes arise from the leftover material of dying large stars (supernova explosions). Smaller stars become dense neutron stars, which lack the massiveness to trap light. If the mass of a star is 3 times greater than that of the Sun, then it becomes a candidate for a black hole. It is important to explain one strange thing to children. When a star collapses, its surface approaches an imaginary surface (event horizon). Time on the star itself becomes slower than that of the observer. When the surface reaches the event horizon, time freezes and the star can no longer collapse - a frozen, collapsing object.

Black holes at the centers of merging galaxies

Larger black holes can appear after a stellar collision. After its launch in December 2004, the NASA telescope was able to detect strong, fleeting flashes of light - gamma rays. Chandra and Hubble then collected data on the event and realized that these flares could be the result of a collision between a black hole and a neutron star, which creates a new black hole.

Although children and parents have already figured it out in the process of education, one point remains a mystery. The holes seem to exist on two different scales. There are many black holes - the remains of massive stars. Typically, they are 10-24 times more massive than the Sun. Scientists constantly see them if an alien star comes critically close. But most black holes exist in isolation and simply cannot be seen. However, judging by the number of stars large enough to be black hole candidates, there must be tens of millions of billions of such black holes in the Milky Way.

There are also supermassive black holes, which are a million or even a billion times larger than our Sun. It is believed that such monsters live in the centers of almost all large galaxies (including ours).

It will be interesting for the little ones to know that for a long time scientists believed that there was no average size for black holes. But data from Chandra, XMM-Newton and Hubble show that they are there.

It is possible that supermassive black holes arise from a chain reaction caused by the collision of stars in compact clusters. Because of this, a lot of massive stars accumulate, which collapse and produce black holes. These clusters then occupy the galactic center, where the black holes merge and become a supermassive member.

You may have realized by now that you won't be able to view a black hole in high quality online because these objects don't emit light. But children will be interested in studying photographs and diagrams created based on the contact of black holes and ordinary matter.

A laconic explanation of the phenomenon goes like this. A black hole is a space-time region whose gravitational attraction is so strong that no object, including light quanta, can leave it.

The black hole was once a massive star. As long as thermonuclear reactions maintain high pressure in its depths, everything remains normal. But over time, the energy supply is depleted and the celestial body, under the influence of its own gravity, begins to shrink. The final stage of this process is the collapse of the stellar core and the formation of a black hole.

• 1. A black hole ejects a jet at high speed
• 2. A disk of matter grows into a black hole
• 3. Black hole
• 4. Detailed diagram of the black hole region
• 5. Size of new observations found

The most common theory is that similar phenomena exist in every galaxy, including the center of our Milky Way. The hole's enormous gravitational force is capable of holding several galaxies around it, preventing them from moving away from each other. The “coverage area” can be different, it all depends on the mass of the star that turned into a black hole, and can be thousands of light years.

Pressure in a black hole. Answers

Bob Bee

We don't know any pressure. In fact, we don't really know what's inside a black hole (BH).

Classic solutions for BHs have a horizon (or two for a rotating BH Kerr solution) where the inner region is causally related to the outer region. In the inner region, space-time is empty, there is nothing there except a singularity, where the curvature of space-time becomes infinite.

Moreover, a person (or particle) walking towards the horizon (and in the coordinate frame of one of them, or in the particle's coordinate frame, it does so over a finite period of time) does not see anything strange happening towards the horizon (possible exception later in this answer ), and inevitably ends up in a singularity, and does it quite quickly. The gravitational effect that the observer experiences inside the horizon increases until it becomes infinite in classical solutions.

The exceptions or caveats to this story are that it does not take quantum gravity into account. We don't have an accepted theory of quantum gravity yet (we have some hypothetical theories like string theory and quantum loop gravity) as we approach the singularity. General relativity becomes invalid and we don't yet know that it is taking over. In fact, there are claims that there is something on the horizon called a firewall, and everything there is destroyed. There are problems with storing physical information in BHs, and some hypotheses are that information freezes at the horizon and is stored there. This entire issue is under active ongoing research.

Perhaps tidal forces can be seen as a kind of pressure. If you end up with a black hole at your feet first, the other gravitational force at different ends of your body will cause you to be stretched and pulled like spaghetti. Google "spaghettification".

Spaggettification is tidal forces, it will be a gravity field with a gradient. Pressure is not like that, it just pushes or pulls, and it is related to field or matter.

Pressure is usually determined by the force per surface area. Since there is no physical dimension "inside" the BH and therefore no surface, there is no way to determine the pressure. In fact, we don't understand anything inside a black hole.

Video What is a Black Hole?

A black hole is a self-sustaining gravitational field concentrated in a highly curved region of space-time (image from www.science.nasa.gov)

A black hole is neither matter nor radiation. With some figurativeness, we can say that this is a self-sustaining gravitational field concentrated in a highly curved region of space-time. Its outer boundary is defined by a closed surface, the event horizon. If the star did not rotate before the collapse, this surface turns out to be a regular sphere, the radius of which coincides with the Schwarzschild radius.

The physical meaning of the horizon is very clear. A light signal sent from its outer vicinity can travel an infinitely long distance. But signals sent from the inner region will not only not cross the horizon, but will inevitably “fall” into the singularity. The horizon is the spatial boundary between events that can become known to terrestrial (and any other) astronomers, and events, information about which under no circumstances will come out.

As expected “according to Schwarzschild,” far from the horizon the attraction of a hole is inversely proportional to the square of the distance, so for a distant observer it manifests itself as an ordinary heavy body. In addition to mass, the hole inherits the moment of inertia of the collapsed star and its electrical charge. And all other characteristics of the predecessor star (structure, composition, spectral type, etc.) fade into oblivion.

Let's send a probe to the hole with a radio station that sends a signal once a second according to onboard time. For a remote observer, as the probe approaches the horizon, the time intervals between signals will increase - in principle, unlimitedly. As soon as the ship crosses the invisible horizon, it will become completely silent for the “over-the-hole” world. However, this disappearance will not be without a trace, since the probe will give up its mass, charge and torque to the hole.