S. TRANKOVSKY

Among the most important and interesting problems of modern physics and astrophysics, Academician V.L. Ginzburg named issues related to black holes (see “Science and Life” No. 11, 12, 1999). The existence of these strange objects was predicted more than two hundred years ago, the conditions leading to their formation were precisely calculated in the late 30s of the 20th century, and astrophysics began to seriously study them less than forty years ago. Today, scientific journals around the world annually publish thousands of articles on black holes.

The formation of a black hole can occur in three ways.

This is how it is customary to depict processes occurring in the vicinity of a collapsing black hole. Over time (Y), the space (X) around it (the shaded area) shrinks, rushing towards the singularity.

The gravitational field of a black hole introduces severe distortions into the geometry of space.

A black hole, invisible through a telescope, reveals itself only by its gravitational influence.

In the powerful gravitational field of a black hole, particle-antiparticle pairs are born.

The birth of a particle-antiparticle pair in the laboratory.

HOW THEY ARISE

A luminous celestial body, having a density equal to that of the Earth, and a diameter two hundred and fifty times greater than the diameter of the Sun, due to the force of its gravity, will not allow its light to reach us. Thus, it is possible that the largest luminous bodies in the Universe remain invisible precisely because of their size.
Pierre Simon Laplace.
Exposition of the world system. 1796

In 1783, the English mathematician John Mitchell, and thirteen years later, independently of him, the French astronomer and mathematician Pierre Simon Laplace, conducted a very strange study. They looked at the conditions under which light would be unable to escape the star.

The logic of the scientists was simple. For any astronomical object (planet or star), it is possible to calculate the so-called escape velocity, or the second cosmic velocity, which allows any body or particle to leave it forever. And in the physics of that time, Newton’s theory reigned supreme, according to which light is a flow of particles (the theory of electromagnetic waves and quanta was still almost a hundred and fifty years away). The escape velocity of particles can be calculated based on the equality of the potential energy on the surface of the planet and the kinetic energy of a body that has “escaped” to an infinitely large distance. This speed is determined by the formula #1#

Where M- mass of the space object, R- its radius, G- gravitational constant.

From this we can easily obtain the radius of a body of a given mass (later called the “gravitational radius” r g "), at which the escape velocity is equal to the speed of light:

This means that a star compressed into a sphere with a radius r g< 2GM/c 2 will stop emitting - the light will not be able to leave it. A black hole will appear in the Universe.

It is easy to calculate that the Sun (its mass is 2.1033 g) will turn into a black hole if it contracts to a radius of approximately 3 kilometers. The density of its substance will reach 10 16 g/cm 3 . The radius of the Earth, compressed into a black hole, would decrease to about one centimeter.

It seemed incredible that there could be forces in nature capable of compressing a star to such an insignificant size. Therefore, the conclusions from the works of Mitchell and Laplace were considered for more than a hundred years to be something of a mathematical paradox that had no physical meaning.

Rigorous mathematical proof that such an exotic object in space was possible was obtained only in 1916. German astronomer Karl Schwarzschild, after analyzing the equations of Albert Einstein's general theory of relativity, obtained an interesting result. Having studied the motion of a particle in the gravitational field of a massive body, he came to the conclusion: the equation loses its physical meaning (its solution turns to infinity) when r= 0 and r = r g.

The points at which the characteristics of the field become meaningless are called singular, that is, special. The singularity at the zero point reflects the pointwise, or, what is the same thing, the centrally symmetric structure of the field (after all, any spherical body - a star or a planet - can be represented as a material point). And points located on a spherical surface with a radius r g, form the very surface from which the escape velocity is equal to the speed of light. In the general theory of relativity it is called the Schwarzschild singular sphere or the event horizon (why will become clear later).

Already based on the example of objects familiar to us - the Earth and the Sun - it is clear that black holes are very strange objects. Even astronomers who deal with matter at extreme values ​​of temperature, density and pressure consider them very exotic, and until recently not everyone believed in their existence. However, the first indications of the possibility of the formation of black holes were already contained in A. Einstein’s general theory of relativity, created in 1915. English astronomer Arthur Eddington, one of the first interpreters and popularizers of the theory of relativity, in the 30s derived a system of equations describing the internal structure of stars. It follows from them that the star is in equilibrium under the influence of oppositely directed gravitational forces and internal pressure created by the movement of hot plasma particles inside the star and the pressure of radiation generated in its depths. This means that the star is a gas ball, in the center of which there is a high temperature, gradually decreasing towards the periphery. From the equations, in particular, it followed that the surface temperature of the Sun was about 5500 degrees (which was quite consistent with the data of astronomical measurements), and in its center it should be about 10 million degrees. This allowed Eddington to make a prophetic conclusion: at this temperature, a thermonuclear reaction “ignites”, sufficient to ensure the glow of the Sun. Atomic physicists of that time did not agree with this. It seemed to them that it was too “cold” in the depths of the star: the temperature there was not enough for the reaction to “go.” To this the enraged theorist replied: “Look for a hotter place!”

And in the end, he turned out to be right: a thermonuclear reaction really occurs in the center of the star (another thing is that the so-called “standard solar model”, based on ideas about thermonuclear fusion, apparently turned out to be incorrect - see, for example, “Science and life" No. 2, 3, 2000). But nevertheless, the reaction in the center of the star takes place, the star shines, and the radiation that arises keeps it in a stable state. But the nuclear “fuel” in the star burns out. The release of energy stops, the radiation goes out, and the force restraining gravitational attraction disappears. There is a limit on the mass of a star, after which the star begins to shrink irreversibly. Calculations show that this happens if the mass of the star exceeds two to three solar masses.

GRAVITATIONAL COLLAPSE

At first, the rate of contraction of the star is small, but its rate continuously increases, since the force of gravity is inversely proportional to the square of the distance. The compression becomes irreversible; there are no forces capable of counteracting self-gravity. This process is called gravitational collapse. The speed of movement of the star's shell towards its center increases, approaching the speed of light. And here the effects of the theory of relativity begin to play a role.

The escape velocity was calculated based on Newtonian ideas about the nature of light. From the point of view of general relativity, phenomena in the vicinity of a collapsing star occur somewhat differently. In its powerful gravitational field, a so-called gravitational redshift occurs. This means that the frequency of radiation coming from a massive object is shifted towards lower frequencies. In the limit, at the boundary of the Schwarzschild sphere, the radiation frequency becomes zero. That is, an observer located outside of it will not be able to find out anything about what is happening inside. That is why the Schwarzschild sphere is called the event horizon.

But decreasing the frequency equals slowing down time, and when the frequency becomes zero, time stops. This means that an outside observer will see a very strange picture: the shell of a star, falling with increasing acceleration, stops instead of reaching the speed of light. From his point of view, the compression will stop as soon as the size of the star approaches gravitational
usu. He will never see even one particle “dive” under the Schwarzschiel sphere. But for a hypothetical observer falling into a black hole, everything will be over in a matter of moments on his watch. Thus, the gravitational collapse time of a star the size of the Sun will be 29 minutes, and a much denser and more compact neutron star will take only 1/20,000 of a second. And here he faces trouble associated with the geometry of space-time near a black hole.

The observer finds himself in a curved space. Near the gravitational radius, gravitational forces become infinitely large; they stretch the rocket with the astronaut-observer into an infinitely thin thread of infinite length. But he himself will not notice this: all his deformations will correspond to the distortions of space-time coordinates. These considerations, of course, refer to an ideal, hypothetical case. Any real body will be torn apart by tidal forces long before approaching the Schwarzschild sphere.

DIMENSIONS OF BLACK HOLES

The size of a black hole, or more precisely, the radius of the Schwarzschild sphere, is proportional to the mass of the star. And since astrophysics does not impose any restrictions on the size of a star, a black hole can be arbitrarily large. If, for example, it arose during the collapse of a star with a mass of 10 8 solar masses (or due to the merger of hundreds of thousands, or even millions of relatively small stars), its radius will be about 300 million kilometers, twice the Earth’s orbit. And the average density of the substance of such a giant is close to the density of water.

Apparently, these are the kind of black holes that are found in the centers of galaxies. In any case, astronomers today count about fifty galaxies, in the centers of which, judging by indirect evidence (discussed below), there are black holes with a mass of about a billion (10 9) solar. Our Galaxy also apparently has its own black hole; Its mass was estimated quite accurately - 2.4. 10 6 ±10% of the mass of the Sun.

The theory suggests that along with such supergiants, black mini-holes with a mass of about 10 14 g and a radius of about 10 -12 cm (the size of an atomic nucleus) should also arise. They could appear in the first moments of the existence of the Universe as a manifestation of very strong inhomogeneity of space-time with colossal energy density. Today, researchers realize the conditions that existed in the Universe at that time at powerful colliders (accelerators using colliding beams). Experiments at CERN earlier this year produced quark-gluon plasma, matter that existed before the emergence of elementary particles. Research into this state of matter continues at Brookhaven, the American accelerator center. It is capable of accelerating particles to energies one and a half to two orders of magnitude higher than the accelerator in
CERN. The upcoming experiment has caused serious concern: will it create a mini-black hole that will bend our space and destroy the Earth?

This fear resonated so strongly that the US government was forced to convene an authoritative commission to examine this possibility. A commission consisting of prominent researchers concluded: the energy of the accelerator is too low for a black hole to arise (this experiment is described in the journal Science and Life, No. 3, 2000).

HOW TO SEE THE INVISIBLE

Black holes emit nothing, not even light. However, astronomers have learned to see them, or rather, to find “candidates” for this role. There are three ways to detect a black hole.

1. It is necessary to monitor the rotation of stars in clusters around a certain center of gravity. If it turns out that there is nothing in this center, and the stars seem to be spinning around an empty space, we can say quite confidently: in this “emptiness” there is a black hole. It was on this basis that the presence of a black hole in the center of our Galaxy was assumed and its mass was estimated.

2. A black hole actively sucks matter into itself from the surrounding space. Interstellar dust, gas, and matter from nearby stars fall onto it in a spiral, forming a so-called accretion disk, similar to the ring of Saturn. (This is precisely the scarecrow in the Brookhaven experiment: a mini-black hole that appeared in the accelerator will begin to suck the Earth into itself, and this process could not be stopped by any force.) Approaching the Schwarzschild sphere, the particles experience acceleration and begin to emit in the X-ray range. This radiation has a characteristic spectrum similar to the well-studied radiation of particles accelerated in a synchrotron. And if such radiation comes from some region of the Universe, we can say with confidence that there must be a black hole there.

3. When two black holes merge, gravitational radiation occurs. It is calculated that if the mass of each is about ten solar masses, then when they merge in a matter of hours, energy equivalent to 1% of their total mass will be released in the form of gravitational waves. This is a thousand times more than the light, heat and other energy that the Sun emitted during its entire existence - five billion years. They hope to detect gravitational radiation with the help of gravitational wave observatories LIGO and others, which are now being built in America and Europe with the participation of Russian researchers (see “Science and Life” No. 5, 2000).

And yet, although astronomers have no doubts about the existence of black holes, no one dares to categorically assert that exactly one of them is located at a given point in space. Scientific ethics and the integrity of the researcher require an unambiguous answer to the question posed, one that does not tolerate discrepancies. It is not enough to estimate the mass of an invisible object; you need to measure its radius and show that it does not exceed the Schwarzschild radius. And even within our Galaxy this problem is not yet solvable. That is why scientists show a certain restraint in reporting their discovery, and scientific journals are literally filled with reports of theoretical work and observations of effects that can shed light on their mystery.

However, black holes have one more property, theoretically predicted, which might make it possible to see them. But, however, under one condition: the mass of the black hole should be much less than the mass of the Sun.

A BLACK HOLE CAN ALSO BE “WHITE”

For a long time, black holes were considered the embodiment of darkness, objects that in a vacuum, in the absence of absorption of matter, emit nothing. However, in 1974, the famous English theorist Stephen Hawking showed that black holes can be assigned a temperature, and therefore should radiate.

According to the concepts of quantum mechanics, vacuum is not emptiness, but a kind of “foam of space-time,” a mishmash of virtual (unobservable in our world) particles. However, quantum energy fluctuations can “eject” a particle-antiparticle pair from the vacuum. For example, in the collision of two or three gamma quanta, an electron and a positron will appear as if out of thin air. This and similar phenomena have been repeatedly observed in laboratories.

It is quantum fluctuations that determine the radiation processes of black holes. If a pair of particles with energies E And -E(the total energy of the pair is zero) occurs in the vicinity of the Schwarzschild sphere, the further fate of the particles will be different. They can annihilate almost immediately or go under the event horizon together. In this case, the state of the black hole will not change. But if only one particle goes below the horizon, the observer will register another, and it will seem to him that it was generated by a black hole. At the same time, a black hole that absorbed a particle with energy -E, will reduce your energy, and with energy E- will increase.

Hawking calculated the rates at which all these processes occur and came to the conclusion: the probability of absorption of particles with negative energy is higher. This means that the black hole loses energy and mass - it evaporates. In addition, it radiates as a completely black body with a temperature T = 6 . 10 -8 M With / M kelvins, where M c - mass of the Sun (2.10 33 g), M- the mass of the black hole. This simple relationship shows that the temperature of a black hole with a mass six times that of the sun is equal to one hundred millionth of a degree. It is clear that such a cold body emits practically nothing, and all the above reasoning remains valid. Mini-holes are another matter. It is easy to see that with a mass of 10 14 -10 30 grams, they are heated to tens of thousands of degrees and white-hot! It should be noted right away, however, that there are no contradictions with the properties of black holes: this radiation is emitted by a layer above the Schwarzschild sphere, and not below it.

So, the black hole, which seemed to be an eternally frozen object, sooner or later disappears, evaporating. Moreover, as she “loses weight,” the rate of evaporation increases, but it still takes an extremely long time. It is estimated that mini-holes weighing 10 14 grams, which appeared immediately after the Big Bang 10-15 billion years ago, should evaporate completely by our time. At the last stage of life, their temperature reaches colossal values, so the products of evaporation must be particles of extremely high energy. Perhaps they are the ones that generate widespread air showers in the Earth's atmosphere - EAS. In any case, the origin of particles of anomalously high energy is another important and interesting problem that can be closely related to no less exciting questions in the physics of black holes.

Black holes are one of the most amazing and at the same time frightening objects in our Universe. They arise at the moment when stars with enormous mass run out of nuclear fuel. Nuclear reactions stop and the stars begin to cool. The body of the star contracts under the influence of gravity and gradually it begins to attract smaller objects to itself, transforming into a black hole.

First studies

Scientific luminaries began studying black holes not so long ago, despite the fact that the basic concepts of their existence were developed back in the last century. The very concept of a “black hole” was introduced in 1967 by J. Wheeler, although the conclusion that these objects inevitably arise during the collapse of massive stars was made back in the 30s of the last century. Everything inside the black hole - asteroids, light, comets absorbed by it - once approached too close to the boundaries of this mysterious object and failed to leave them.

Boundaries of black holes

The first of the boundaries of a black hole is called the static limit. This is the boundary of the region, entering which a foreign object can no longer be at rest and begins to rotate relative to the black hole in order to prevent itself from falling into it. The second boundary is called the event horizon. Everything inside a black hole once passed its outer boundary and moved towards the singularity point. According to scientists, here the substance flows into this central point, the density of which tends to infinity. People cannot know what laws of physics operate inside objects with such density, and therefore it is impossible to describe the characteristics of this place. In the literal sense of the word, it is a “black hole” (or perhaps a “gap”) in humanity’s knowledge of the world around us.

Structure of black holes

The event horizon is the impenetrable boundary of a black hole. Inside this boundary there is a zone that even objects whose movement speed is equal to the speed of light cannot leave. Even the quanta of light itself cannot leave the event horizon. Once at this point, no object can escape from the black hole. By definition, we cannot find out what is inside a black hole - after all, in its depths there is a so-called singularity point, which is formed due to the extreme compression of matter. Once an object falls inside the event horizon, from that moment on it will never be able to escape from it again and become visible to observers. On the other hand, those inside black holes cannot see anything happening outside.

The size of the event horizon surrounding this mysterious cosmic object is always directly proportional to the mass of the hole itself. If its mass is doubled, then the outer boundary will become twice as large. If scientists could find a way to turn the Earth into a black hole, then the size of the event horizon would be only 2 cm in cross section.

Main categories

As a rule, the mass of the average black hole is approximately equal to three solar masses or more. Of the two types of black holes, stellar and supermassive ones are distinguished. Their mass exceeds the mass of the Sun by several hundred thousand times. Stars are formed after the death of large celestial bodies. Regular-mass black holes appear after the life cycle of large stars ends. Both types of black holes, despite their different origins, have similar properties. Supermassive black holes are located at the centers of galaxies. Scientists suggest that they were formed during the formation of galaxies due to the merger of stars closely adjacent to each other. However, these are only guesses, not confirmed by facts.

What's inside a black hole: guesses

Some mathematicians believe that inside these mysterious objects of the Universe there are so-called wormholes - transitions to other Universes. In other words, at the point of singularity there is a space-time tunnel. This concept has served many writers and directors. However, the vast majority of astronomers believe that there are no tunnels between the Universes. However, even if they did exist, there is no way for humans to know what is inside a black hole.

There is another concept, according to which at the opposite end of such a tunnel there is a white hole, from where a gigantic amount of energy flows from our Universe to another world through black holes. However, at this stage of the development of science and technology, travel of this kind is out of the question.

Connection with the theory of relativity

Black holes are one of the most amazing predictions of A. Einstein. It is known that the gravitational force that is created on the surface of any planet is inversely proportional to the square of its radius and directly proportional to its mass. For this celestial body, we can define the concept of second cosmic velocity, which is necessary to overcome this gravitational force. For the Earth it is equal to 11 km/sec. If the mass of the celestial body increases, and the diameter, on the contrary, decreases, then the second cosmic velocity may eventually exceed the speed of light. And since, according to the theory of relativity, no object can move faster than the speed of light, an object is formed that does not allow anything to escape beyond its limits.

In 1963, scientists discovered quasars - space objects that are giant sources of radio emission. They are located very far from our galaxy - their distance is billions of light years from Earth. To explain the extremely high activity of quasars, scientists have introduced the hypothesis that black holes are located inside them. This point of view is now generally accepted in scientific circles. Research conducted over the past 50 years has not only confirmed this hypothesis, but also led scientists to the conclusion that there are black holes at the center of every galaxy. There is also such an object in the center of our galaxy, its mass is 4 million solar masses. This black hole is called Sagittarius A, and because it is closest to us, it is the one most studied by astronomers.

Hawking radiation

This type of radiation, discovered by the famous physicist Stephen Hawking, significantly complicates the life of modern scientists - because of this discovery, many difficulties have arisen in the theory of black holes. In classical physics there is the concept of vacuum. This word denotes complete emptiness and absence of matter. However, with the development of quantum physics, the concept of vacuum was modified. Scientists have found that it is filled with so-called virtual particles - under the influence of a strong field they can turn into real ones. In 1974, Hawking discovered that such transformations can occur in the strong gravitational field of a black hole - near its outer boundary, the event horizon. Such a birth is paired - a particle and an antiparticle appear. As a rule, the antiparticle is doomed to fall into a black hole, and the particle flies away. As a result, scientists observe some radiation around these space objects. This is called Hawking radiation.

During this radiation, the matter inside the black hole slowly evaporates. The hole loses mass, and the intensity of the radiation is inversely proportional to the square of its mass. The intensity of Hawking radiation is negligible by cosmic standards. If we assume that there is a hole with the mass of 10 suns, and neither light nor any material objects fall on it, then even in this case the time for its decay will be monstrously long. The life of such a hole will exceed the entire existence of our Universe by 65 orders of magnitude.

Question about saving information

One of the main problems that appeared after the discovery of Hawking radiation is the problem of information loss. It is connected with a question that seems very simple at first glance: what happens when a black hole evaporates completely? Both theories - both quantum physics and classical - deal with the description of the state of a system. Having information about the initial state of the system, using theory it is possible to describe how it will change.

At the same time, in the process of evolution, information about the initial state is not lost - a kind of law on the preservation of information operates. But if the black hole evaporates completely, then the observer loses information about that part of the physical world that once fell into the hole. Stephen Hawking believed that information about the initial state of the system is somehow restored after the black hole has completely evaporated. But the difficulty is that, by definition, information transfer from a black hole is impossible - nothing can leave the event horizon.

What happens if you fall into a black hole?

It is believed that if in some incredible way a person could get to the surface of a black hole, then it would immediately begin to pull him in its direction. Ultimately, the person would become so stretched that he would become a stream of subatomic particles moving towards a point of singularity. It is, of course, impossible to prove this hypothesis, because scientists are unlikely to ever be able to find out what happens inside black holes. Now some physicists say that if a person fell into a black hole, he would have a clone. The first of its versions would be immediately destroyed by a stream of hot particles of Hawking radiation, and the second would pass through the event horizon without the possibility of returning back.

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Consider the mysterious and invisible black holes in the Universe: interesting facts, Einstein's research, supermassive and intermediate types, theory, structure.

- one of the most interesting and mysterious objects in outer space. They have a high density, and the gravitational force is so powerful that even light cannot escape beyond its limits.

Albert Einstein first spoke about black holes in 1916, when he created the general theory of relativity. The term itself originated in 1967 thanks to John Wheeler. And the first black hole was “seen” in 1971.

The classification of black holes includes three types: stellar mass black holes, supermassive black holes and intermediate mass black holes. Be sure to watch the video about black holes to learn many interesting facts and get to know these mysterious cosmic formations better.

Interesting facts about black holes

• If you find yourself inside a black hole, gravity will stretch you. But there is no need to be afraid, because you will die before you reach the singularity. A 2012 study suggested that quantum effects turn the event horizon into a wall of fire that turns you into a pile of ash.
• Black holes don't "suck". This process is caused by a vacuum, which is not present in this formation. So the material just falls off.
• The first black hole was Cygnus X-1, found by rockets with Geiger counters. In 1971, scientists received a radio signal from Cygnus X-1. This object became the subject of a dispute between Kip Thorne and Stephen Hawking. The latter believed that it was not a black hole. In 1990, he admitted defeat.
• Tiny black holes may have appeared immediately after the Big Bang. Rapidly rotating space compressed some areas into dense holes, less massive than the Sun.
• If the star gets too close, it could be torn apart.
• It is generally estimated that there are up to a billion stellar black holes with three times the mass of the Sun.
• If we compare string theory and classical mechanics, the former gives rise to more varieties of massive giants.

The danger of black holes

When a star runs out of fuel, it can begin the process of self-destruction. If its mass was three times that of the Sun, then the remaining core would become a neutron star or a white dwarf. But the larger star transforms into a black hole.

Such objects are small, but have incredible density. Imagine that in front of you is an object the size of a city, but its mass is three times that of the Sun. This creates an incredibly huge gravitational force that attracts dust and gas, increasing its size. You will be surprised, but there may be several hundred million stellar black holes.

Supermassive black holes

Of course, nothing in the universe compares to the awesomeness of supermassive black holes. They exceed the solar mass by billions of times. It is believed that such objects exist in almost every galaxy. Scientists do not yet know all the intricacies of the formation process. Most likely, they grow due to the accumulation of mass from surrounding dust and gas.

They may owe their size to the merger of thousands of small black holes. Or an entire star cluster could collapse.

Black holes at the centers of galaxies

Astrophysicist Olga Silchenko about the discovery of a supermassive black hole in the Andromeda nebula, John Kormendy's research and dark gravitating bodies:

The nature of cosmic radio sources

Astrophysicist Anatoly Zasov about synchrotron radiation, black holes in the nuclei of distant galaxies and neutral gas:

Intermediate black holes

Not long ago, scientists found a new type - intermediate mass black holes. They can form when stars in a cluster collide, causing a chain reaction. As a result, they fall into the center and form a supermassive black hole.

In 2014, astronomers discovered an intermediate type in the arm of a spiral galaxy. They are very difficult to find because they can be located in unpredictable places.

Micro black holes

Physicist Eduard Boos on the safety of the LHC, the birth of a microblack hole and the concept of a membrane:

Black hole theory

Black holes are extremely massive objects, but span a relatively modest amount of space. In addition, they have enormous gravity, preventing objects (and even light) from leaving their territory. However, it is impossible to see them directly. Researchers have to look at the radiation produced when a black hole feeds.

Interestingly, it happens that matter heading towards a black hole bounces off the event horizon and is thrown out. In this case, bright jets of material are formed, moving at relativistic speeds. These emissions can be detected over long distances.

- amazing objects in which the force of gravity is so enormous that it can bend light, warp space and distort time.

In black holes, three layers can be distinguished: the outer and inner event horizon and the singularity.

The event horizon of a black hole is the boundary where light has no chance of escaping. Once a particle crosses this line, it will not be able to leave. The inner region where the mass of a black hole is located is called a singularity.

If we speak from the position of classical mechanics, then nothing can escape a black hole. But quantum makes its own correction. The fact is that every particle has an antiparticle. They have the same masses, but different charges. If they intersect, they can annihilate each other.

When such a pair appears outside the event horizon, one of them can be pulled in and the other can be repelled. Because of this, the horizon can shrink and the black hole can collapse. Scientists are still trying to study this mechanism.

Accretion

Astrophysicist Sergei Popov on supermassive black holes, planet formation and accretion of matter in the early Universe:

The most famous black holes

Frequently asked questions about black holes

More capaciously, a black hole is a certain area in space in which such a huge amount of mass is concentrated that not a single object can escape the gravitational influence. When it comes to gravity, we rely on the general theory of relativity proposed by Albert Einstein. To understand the details of the object under study, we will move step by step.

Let's imagine that you are on the surface of the planet and are throwing a boulder. If you don't have the power of the Hulk, you won't be able to exert enough force. Then the stone will rise to a certain height, but under the pressure of gravity it will fall back. If you have the hidden potential of a green strongman, then you are able to give the object sufficient acceleration, thanks to which it will completely leave the zone of gravitational influence. This is called "escape velocity".

If we break it down into a formula, this speed depends on the planetary mass. The larger it is, the more powerful the gravitational grip. The speed of departure will depend on where exactly you are: the closer to the center, the easier it is to get out. The speed of departure of our planet is 11.2 km/s, but it is 2.4 km/s.

We are getting closer to the most interesting part. Let's say you have an object with an incredible concentration of mass collected in a tiny place. In this case, the escape velocity exceeds the speed of light. And we know that nothing moves faster than this indicator, which means that no one will be able to overcome such force and escape. Even a light beam cannot do this!

Back in the 18th century, Laplace pondered the extreme concentration of mass. Following general relativity, Karl Schwarzschild was able to find a mathematical solution to the theory's equation to describe such an object. Further contributions were made by Oppenheimer, Wolkoff and Snyder (1930s). From that moment on, people began to discuss this topic seriously. It became clear: when a massive star runs out of fuel, it is unable to withstand the force of gravity and is bound to collapse into a black hole.

In Einstein's theory, gravity is a manifestation of curvature in space and time. The fact is that the usual geometric rules do not work here and massive objects distort space-time. The black hole has bizarre properties, so its distortion is most clearly visible. For example, an object has an “event horizon.” This is the surface of the sphere marking the line of the hole. That is, if you step over this limit, then there is no turning back.

Literally, this is the place where the escape speed is equal to the speed of light. Outside this place, the escape velocity is inferior to the speed of light. But if your rocket is able to accelerate, then there will be enough energy to escape.

The horizon itself is quite strange in terms of geometry. If you are far away, you will feel like you are looking at a static surface. But if you get closer, you realize that it is moving outward at the speed of light! Now I understand why it is easy to enter, but so difficult to escape. Yes, this is very confusing, because in fact the horizon stands still, but at the same time it rushes at the speed of light. It's like the situation with Alice, who had to run as fast as possible just to stay in place.

When hitting the horizon, space and time experience such a strong distortion that the coordinates begin to describe the roles of radial distance and switching time. That is, “r”, marking the distance from the center, becomes temporary, and “t” is now responsible for “spatiality”. As a result, you will not be able to stop moving with a lower index of r, just as you will not be able to get into the future in normal time. You will come to a singularity where r = 0. You can throw rockets, run the engine to maximum, but you cannot escape.

The term "black hole" was coined by John Archibald Wheeler. Before that, they were called “cooled stars.”

Physicist Emil Akhmedov on the study of black holes, Karl Schwarzschild and giant black holes:

There are two ways to calculate how big something is. You can name the mass or how large the area occupies. If we take the first criterion, then there is no specific limit on the massiveness of a black hole. You can use any amount as long as you can compress it to the required density.

Most of these formations appeared after the death of massive stars, so one would expect that their weight should be equivalent. The typical mass for such a hole would be 10 times that of the sun - 10 31 kg. In addition, each galaxy must be home to a central supermassive black hole, whose mass exceeds the solar one a million times - 10 36 kg.

The more massive the object, the more mass it covers. The horizon radius and mass are directly proportional, that is, if a black hole weighs 10 times more than another, then its radius is 10 times larger. The radius of a hole with solar massiveness is 3 km, and if it is a million times larger, then 3 million km. These seem to be incredibly massive things. But let's not forget that these are standard concepts for astronomy. The solar radius reaches 700,000 km, and that of a black hole is 4 times greater.

Let's say that you are unlucky and your ship is inexorably moving towards a supermassive black hole. There's no point in fighting. You simply turn off the engines and head towards the inevitable. What to expect?

Let's start with weightlessness. You are in free fall, so the crew, ship and all the parts are weightless. The closer you get to the center of the hole, the stronger the tidal gravitational forces are felt. For example, your feet are closer to the center than your head. Then you begin to feel like you are being stretched. As a result, you will simply be torn apart.

These forces are unnoticeable until you get within 600,000 km of the center. This is already after the horizon. But we are talking about a huge object. If you fall into a hole with the mass of the sun, then the tidal forces would engulf you 6000 km from the center and tear you apart before you reach the horizon (that's why we send you to the big one so that you can die already inside the hole, and not on the approach) .

What's inside? I don't want to disappoint, but nothing remarkable. Some objects may be distorted in appearance and nothing else out of the ordinary. Even after crossing the horizon, you will see things around you as they move with you.

How long will all this take? Everything depends on your distance. For example, you started from a point of rest where the singularity is 10 times the radius of the hole. It will take only 8 minutes to approach the horizon, and then another 7 seconds to enter the singularity. If you fall into a small black hole, everything will happen faster.

As soon as you cross the horizon, you can shoot rockets, scream and cry. You have 7 seconds to do all this until you get into the singularity. But nothing will save you. So just enjoy the ride.

Let's say you are doomed and fall into a hole, and your boyfriend watches from afar. Well, he'll see things differently. You will notice that you slow down as you get closer to the horizon. But even if a person sits for a hundred years, he will not wait until you reach the horizon.

Let's try to explain. The black hole could have emerged from a collapsing star. Since the material is destroyed, Kirill (let him be your friend) sees it decreasing, but will never notice it approaching the horizon. That's why they were called "frozen stars" because they seem to freeze at a certain radius.

What's the matter? Let's call it an optical illusion. Infinity is not needed to form a hole, just as it is not necessary to cross the horizon. As you approach, the light takes longer to reach Kirill. More precisely, the real-time radiation from your transition will be recorded at the horizon forever. You have long stepped over the line, and Kirill is still observing the light signal.

Or you can approach from the other side. Time drags longer near the horizon. For example, you have a super-powerful ship. You managed to get closer to the horizon, stay there for a couple of minutes and get out alive to Kirill. Who will you see? Old man! After all, time passed much slower for you.

What is true then? Illusion or game of time? It all depends on the coordinate system used to describe the black hole. If you rely on Schwarzschild coordinates, then when crossing the horizon, the time coordinate (t) is equal to infinity. But the metrics from this system provide a blurred view of what is happening near the object itself. At the horizon line, all coordinates are distorted (singularity). But you can use both coordinate systems, so the two answers are valid.

In reality, you will simply become invisible, and Kirill will stop seeing you before much time has passed. Don't forget about redshift. You emit observable light at a certain wavelength, but Kirill will see it at a longer one. The waves lengthen as they approach the horizon. In addition, do not forget that radiation occurs in certain photons.

For example, at the moment of transition you will send the last photon. It will reach Kirill at a certain finite time (about an hour for a supermassive black hole).

Of course not. Don't forget about the existence of the event horizon. This is the only area you can't get out of. It is enough just not to approach her and feel calm. Moreover, from a safe distance this object will seem very ordinary to you.

Hawking's Information Paradox

Physicist Emil Akhmedov on the effect of gravity on electromagnetic waves, the information paradox of black holes and the principle of predictability in science:

Don't panic, as the Sun will never transform into such an object because it simply doesn't have enough mass. Moreover, it will retain its current appearance for another 5 billion years. Then it will move to the red giant stage, absorbing Mercury, Venus and thoroughly frying our planet, and then become an ordinary white dwarf.

But let's indulge in fantasy. So the Sun became a black hole. To begin with, we will immediately be enveloped in darkness and cold. The Earth and other planets will not be sucked into the hole. They will continue to orbit the new object in normal orbits. Why? Because the horizon will reach only 3 km, and gravity will not be able to do anything to us.

Yes. Naturally, we cannot rely on visible observation, since the light cannot escape. But there is circumstantial evidence. For example, you see an area that could contain a black hole. How can I check this? Start by measuring the mass. If it is clear that in one area there is too much of it or it is seemingly invisible, then you are on the right track. There are two search points: the galactic center and binary systems with X-ray radiation.

Thus, massive central objects were found in 8 galaxies, whose nuclear mass ranges from a million to a billion solar. Mass is calculated by observing the speed of rotation of stars and gas around the center. The faster, the greater the mass must be to keep them in orbit.

These massive objects are considered black holes for two reasons. Well, there are simply no more options. There is nothing more massive, darker and more compact. In addition, there is a theory that all active and large galaxies have such a monster hiding in the center. But still this is not 100% proof.

But two recent findings speak in favor of the theory. A “water maser” system (a powerful source of microwave radiation) near the nucleus was noticed in the nearest active galaxy. Using an interferometer, scientists mapped the distribution of gas velocities. That is, they measured the speed within half a light year at the galactic center. This helped them understand that there was a massive object inside, whose radius reached half a light year.

The second find is even more convincing. Researchers using X-rays stumbled upon a spectral line of the galactic core, indicating the presence of atoms nearby, the speed of which is incredibly high (1/3 the speed of light). In addition, the emission corresponded to a redshift that corresponds to the horizon of the black hole.

Another class can be found in the Milky Way. These are stellar black holes that form after a supernova explosion. If they existed separately, then even close up we would hardly notice it. But we are lucky, because most exist in dual systems. They are easy to find, since the black hole will pull the mass of its neighbor and influence it with gravity. The “pulled out” material forms an accretion disk, in which everything heats up and therefore creates strong radiation.

Let's assume you managed to find a binary system. How do you understand that a compact object is a black hole? Again we turn to the masses. To do this, measure the orbital speed of a nearby star. If the mass is incredibly huge with such small dimensions, then there are no more options left.

This is a complex mechanism. Stephen Hawking raised a similar topic back in the 1970s. He said that black holes are not really “black.” There are quantum mechanical effects that cause it to create radiation. Gradually the hole begins to shrink. The rate of radiation increases with decreasing mass, so the hole emits more and more and accelerates the process of compression until it dissolves.

However, this is only a theoretical scheme, because no one can say exactly what happens at the last stage. Some people think that a small but stable trace remains. Modern theories have not yet come up with anything better. But the process itself is incredible and complex. It is necessary to calculate parameters in curved space-time, and the results themselves cannot be verified under normal conditions.

The Law of Conservation of Energy can be used here, but only for short durations. The universe can create energy and mass from scratch, but they must quickly disappear. One of the manifestations is vacuum fluctuations. Pairs of particles and antiparticles grow out of nowhere, exist for a certain short period of time and die in mutual destruction. When they appear, the energy balance is disrupted, but everything is restored after disappearance. It seems fantastic, but this mechanism has been confirmed experimentally.

Let's say one of the vacuum fluctuations acts near the horizon of a black hole. Perhaps one of the particles falls in, and the second runs away. The one who escapes takes some of the energy of the hole with her and can fall into the eyes of the observer. It will seem to him that a dark object has simply released a particle. But the process repeats itself, and we see a continuous stream of radiation from the black hole.

We've already said that Kirill feels like you need infinity to step over the horizon line. In addition, it was mentioned that black holes evaporate after a finite period of time. So, when you reach the horizon, the hole will disappear?

No. When we described Kirill's observations, we did not talk about the evaporation process. But, if this process is present, then everything changes. Your friend will see you fly across the horizon at the exact moment of evaporation. Why?

An optical illusion dominates Kirill. The emitted light in the event horizon takes a long time to reach its friend. If the hole lasts forever, then the light can travel indefinitely, and Kirill will not wait for the transition. But, if the hole has evaporated, then nothing will stop the light, and it will reach the guy at the moment of the explosion of radiation. But you don’t care anymore, because you died in the singularity long ago.

The formulas of the general theory of relativity have an interesting feature - symmetry in time. For example, in any equation you can imagine that time flows backwards and get a different, but still correct, solution. If we apply this principle to black holes, then a white hole is born.

A black hole is a defined area from which nothing can escape. But the second option is a white hole into which nothing can fall. In fact, she pushes everything away. Although, from a mathematical point of view, everything looks smooth, this does not prove their existence in nature. Most likely, there are none, and there is no way to find out.

Up to this point we have talked about the classics of black holes. They do not rotate and have no electrical charge. But in the opposite version, the most interesting thing begins. For example, you can get inside but avoid the singularity. Moreover, its “inside” is capable of contacting a white hole. That is, you will find yourself in a kind of tunnel, where the black hole is the entrance and the white hole is the exit. This combination is called a wormhole.

Interestingly, a white hole can be located anywhere, even in another Universe. If we know how to control such wormholes, then we will provide fast transportation to any area of ​​​​space. And even cooler is the possibility of time travel.

But don't pack your backpack until you know a few things. Unfortunately, there is a high probability that there are no such formations. We have already said that white holes are a conclusion from mathematical formulas, and not a real and confirmed object. And all observed black holes create matter falling and do not form wormholes. And the final stop is the singularity.

Mysterious and elusive black holes. The laws of physics confirm the possibility of their existence in the universe, but many questions still remain. Numerous observations show that holes exist in the universe and there are more than a million of these objects.

What are black holes?

Back in 1915, when solving Einstein’s equations, such a phenomenon as “black holes” was predicted. However, the scientific community became interested in them only in 1967. They were then called “collapsed stars”, “frozen stars”.

Nowadays, a black hole is a region of time and space that has such gravity that even a ray of light cannot escape from it.

How are black holes formed?

There are several theories for the appearance of black holes, which are divided into hypothetical and realistic. The simplest and most widespread realistic one is the theory of gravitational collapse of large stars.

When a sufficiently massive star, before “death,” grows in size and becomes unstable, using up its last fuel. At the same time, the mass of the star remains unchanged, but its size decreases as the so-called densification occurs. In other words, when compacted, the heavy core “falls” into itself. In parallel with this, compaction leads to a sharp increase in the temperature inside the star and the outer layers of the celestial body tear off, from which new stars are formed. At the same time, in the center of the star, the core falls into its own “center.” As a result of the action of gravitational forces, the center collapses to a point - that is, the gravitational forces are so strong that they absorb the compacted core. This is how a black hole is born, which begins to distort space and time so that even light cannot escape from it.

At the center of all galaxies is a supermassive black hole. According to Einstein's theory of relativity:

“Any mass distorts space and time.”

Now imagine how much a black hole distorts time and space, because its mass is enormous and at the same time squeezed into an ultra-small volume. This ability causes the following oddity:

“Black holes have the ability to practically stop time and compress space. Because of this extreme distortion, the holes become invisible to us.”

If black holes are not visible, how do we know they exist?

Yes, even though a black hole is invisible, it should be noticeable due to the matter that falls into it. As well as stellar gas, which is attracted by a black hole, when approaching the event horizon, the temperature of the gas begins to rise to ultra-high values, which leads to a glow. This is why black holes glow. Thanks to this, albeit weak, glow, astronomers and astrophysicists explain the presence in the center of the galaxy of an object with a small volume but a huge mass. Currently, as a result of observations, about 1000 objects have been discovered that are similar in behavior to black holes.

Black holes and galaxies

How can black holes affect galaxies? This question plagues scientists all over the world. There is a hypothesis according to which it is the black holes located in the center of the galaxy that influence its shape and evolution. And that when two galaxies collide, black holes merge and during this process such a huge amount of energy and matter is released that new stars are formed.

Types of black holes

• According to existing theory, there are three types of black holes: stellar, supermassive, and miniature. And each of them was formed in a special way.
• - Black holes of stellar masses, it grows to enormous sizes and collapses.
  - Supermassive black holes, which can have a mass equivalent to millions of Suns, are likely to exist at the centers of almost all galaxies, including our Milky Way. Scientists still have different hypotheses for the formation of supermassive black holes. So far, only one thing is known - supermassive black holes are a by-product of the formation of galaxies. Supermassive black holes - they differ from ordinary ones in that they have a very large size, but paradoxically low density.
• - No one has yet been able to detect a miniature black hole that would have a mass less than the Sun. It is possible that miniature holes could have formed shortly after the "Big Bang", which is the exact beginning of the existence of our universe (about 13.7 billion years ago).
• - Quite recently, a new concept was introduced as “white black holes”. This is still a hypothetical black hole, which is the opposite of a black hole. Stephen Hawking actively studied the possibility of the existence of white holes.
• - Quantum black holes - they exist only in theory so far. Quantum black holes can be formed when ultra-small particles collide as a result of a nuclear reaction.
• - Primary black holes are also a theory. They were formed immediately after their origin.

At the moment, there are a large number of open questions that have yet to be answered by future generations. For example, can so-called “wormholes” really exist, with the help of which one can travel through space and time. What exactly happens inside a black hole and what laws these phenomena obey. And what about the disappearance of information in a black hole?

Black holes are some of the most powerful and mysterious objects in the Universe. They are formed after the destruction of a star.

Nasa has compiled a series of stunning images of supposed black holes in the vastness of space.

Here is a photo of the nearby galaxy Centaurus A, taken by the Chandra X-Ray Observatory. This shows the influence of a supermassive black hole within a galaxy.

Nasa recently announced that a black hole is being born from an exploding star in a nearby galaxy. According to Discovery News, this hole is located in the M-100 galaxy, located 50 million years from Earth.

Here's another very interesting photo from Chandra Observatory showing the galaxy M82. Nasa believes what is pictured could be the starting points for two supermassive black holes. Researchers suggest that the formation of black holes will begin when stars exhaust their resources and burn out. They will be crushed by their own gravitational weight.

Scientists associate the existence of black holes with Einstein's theory of relativity. Experts are using Einstein's understanding of gravity to determine the enormous gravitational force of a black hole. In the presented photo, information from the Chandra X-Ray Observatory matches images obtained from the Hubble Space Telescope. Nasa believes that these two black holes have been spiraling towards each other for 30 years, and over time they could become one big black hole.

This is the most powerful black hole in the cosmic galaxy M87. Subatomic particles moving almost at the speed of light indicate that there is a supermassive black hole at the center of this galaxy. It is believed that it “absorbed” matter equal to 2 million of our suns.

Nasa believes this image shows two supermassive black holes colliding to form a system. Or is it the so-called “slingshot effect”, as a result of which a system is formed from 3 black holes. When stars are supernovae, they have the ability to collapse and form again, resulting in the formation of black holes.

This artistic rendering shows a black hole sucking gas from a nearby star. A black hole is this color because its gravitational field is so dense that it absorbs light. Black holes are invisible, so scientists only speculate about their existence. Their size can be equal to the size of just 1 atom or a billion suns.

This artistic rendering shows a quasar, which is a supermassive black hole surrounded by spinning particles. This quasar is located at the center of the galaxy. Quasars are in the early stages of black hole formation, yet they can exist for billions of years. Still, it is believed that they were formed in ancient eras of the Universe. It is assumed that all the “new” quasars were simply hidden from our view.

The Spitzer and Hubble telescopes have captured false colored jets of particles shooting out of a giant, powerful black hole. These jets are believed to extend across 100,000 light-years of space, as large as the Milky Way of our galaxy. Different colors appear from different light waves. There is a powerful black hole in our galaxy, Sagittarius A. Nasa believes that its mass is equal to 4 million of our suns.

This image shows a microquasar, thought to be a smaller black hole with the same mass as a star. If you fell into a black hole, you would cross the time horizon at its boundary. Even if you are not crushed by gravity, you will never return back from a black hole. You will be impossible to see in a dark space. Every traveler into a black hole will be torn apart by the force of gravity.

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