The concept of a black hole is known to everyone - from schoolchildren to the elderly, it is used in science and fiction literature, in the yellow media and on scientific conferences. But not everyone knows what exactly these holes are.

From the history of black holes

1783 The first hypothesis for the existence of such a phenomenon as a black hole was put forward in 1783 by the English scientist John Michell. In his theory, he combined two creations of Newton - optics and mechanics. Michell's idea was this: if light is a stream of tiny particles, then, like all other bodies, particles should experience attraction gravitational field. It turns out that the more massive the star, the more difficult it is for light to resist its attraction. 13 years after Michell, the French astronomer and mathematician Laplace put forward (most likely independently of his British counterpart) a similar theory.

1915 However, all their works remained unclaimed until the beginning of the 20th century. In 1915, Albert Einstein published the General Theory of Relativity and showed that gravity is a curvature of space-time caused by matter, and a few months later, the German astronomer and theoretical physicist Karl Schwarzschild used it to solve a specific astronomical problem. He explored the structure of the curved space-time around the Sun and rediscovered the phenomenon of black holes.

(John Wheeler coined the term "black holes")

1967 American physicist John Wheeler outlined a space that can be crumpled, like a piece of paper, into an infinitesimal point and designated the term "Black Hole".

1974 British physicist Stephen Hawking proved that black holes, although they swallow matter without a return, can emit radiation and eventually evaporate. This phenomenon is called "Hawking radiation".

2013 The latest research on pulsars and quasars, as well as the discovery of cosmic microwave background radiation, has finally made it possible to describe the very concept of black holes. In 2013, the gas cloud G2 came very close to the black hole and is likely to be absorbed by it, observing the unique process provides great opportunities for new discoveries of black hole features.

(Massive object Sagittarius A *, its mass is 4 million times greater than the Sun, which implies a cluster of stars and the formation of a black hole)

2017. A group of scientists from the Event Horizon Telescope collaboration of several countries, linking eight telescopes from different points of the Earth's continents, carried out observations of a black hole, which is a supermassive object and is located in the M87 galaxy, the constellation Virgo. The mass of the object is 6.5 billion (!) solar masses, gigantic times larger than the massive object Sagittarius A *, for comparison, the diameter is slightly less than the distance from the Sun to Pluto.

The observations were carried out in several stages, starting from the spring of 2017 and during the periods of 2018. The amount of information was calculated in petabytes, which then had to be deciphered and a genuine image of an ultra-distant object obtained. Therefore, it took another two whole years to pre-scan all the data and combine them into one whole.

2019 The data was successfully decoded and brought into view, producing the first ever image of a black hole.

(The first ever image of a black hole in the M87 galaxy in the constellation Virgo)

Image resolution allows you to see the shadow of the point of no return in the center of the object. The image was obtained as a result of interferometric observations with an extra long baseline. These are the so-called synchronous observations of one object from several radio telescopes, interconnected by a network and located in different parts. the globe directed in one direction.

What are black holes really?

A laconic explanation of the phenomenon sounds 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.

A black hole was once a massive star. As long as thermonuclear reactions maintain high pressure in its bowels, everything remains normal. But over time, the supply of energy 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. Ejection of a black hole jet at high speed


• 2. A disk of matter grows into a black hole


• 3. Black hole


• 4. Detailed scheme of the black hole region


• 5. Size of found new observations

The most common theory says that there are similar phenomena in every galaxy, including in the center of our Milky Way. The huge gravity of the hole 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 has turned into a black hole, and can be thousands of light years.

Schwarzschild radius

The main property of a black hole is that any matter that gets into it can never return. The same applies to light. At their core, holes are bodies that completely absorb all the light that falls on them and do not emit their own. Such objects can visually appear as clots of absolute darkness.

• 1. Moving matter at half the speed of light


• 2. Photon ring


• 3. Inner photon ring


• 4. The event horizon in a black hole

Based on Einstein's General Theory of Relativity, if a body approaches a critical distance from the center of the hole, it can no longer return. This distance is called the Schwarzschild radius. What exactly happens within this radius is not known for certain, but there is the most common theory. It is believed that all the matter of a black hole is concentrated in an infinitely small point, and in its center there is an object with infinite density, which scientists call a singular perturbation.

How does it fall into a black hole

(In the picture, the black hole of Sagittarius A * looks like an extremely bright cluster of light)

Not so long ago, in 2011, scientists discovered a gas cloud, giving it the simple name G2, which emits unusual light. Such a glow can give friction in gas and dust, caused by the action of the black hole Sagittarius A * and which rotate around it in the form of an accretion disk. Thus, we become observers of the amazing phenomenon of the absorption of a gas cloud by a supermassive black hole.

According to recent studies, the closest approach to a black hole will occur in March 2014. We can recreate a picture of how this exciting spectacle will play out.

• 1. When it first appears in the data, a gas cloud resembles a huge ball of gas and dust.


• 2. Now, as of June 2013, the cloud is tens of billions of kilometers away from the black hole. It falls into it at a speed of 2500 km / s.


• 3. The cloud is expected to pass the black hole, but the tidal forces caused by the difference in attraction acting on the leading and trailing edges of the cloud will cause it to become more and more elongated.


• 4. After the cloud is broken, most of it will most likely merge into the accretion disk around Sagittarius A*, generating in it shock waves. The temperature will rise to several million degrees.


• 5. Part of the cloud will fall directly into the black hole. No one knows exactly what will happen to this substance, but it is expected that in the process of falling it will emit powerful streams. x-rays and no one else will see it.

Video: black hole swallows a gas cloud

(Computer simulation of how much of the G2 gas cloud will be destroyed and consumed by the black hole Sagittarius A*)

What's inside a black hole

There is a theory that claims that a black hole inside is practically empty, and all its mass is concentrated in an incredibly small point located in its very center - a singularity.

According to another theory that has existed for half a century, everything that falls into a black hole goes into another universe located in the black hole itself. Now this theory is not the main one.

And there is a third, most modern and tenacious theory, according to which everything that falls into a black hole dissolves in the vibrations of strings on its surface, which is designated as the event horizon.

So what is the event horizon? It is impossible to look inside a black hole even with a super-powerful telescope, since even light, getting inside a giant cosmic funnel, has no chance to emerge back. Everything that can be somehow considered is in its immediate vicinity.

The event horizon is a conditional line of the surface from under which nothing (neither gas, nor dust, nor stars, nor light) can escape. And this is the very mysterious point of no return in the black holes of the Universe.

Between the French and the British there is sometimes a half-joking, and sometimes a serious controversy: who should be considered the discoverer of the possibility of the existence of invisible stars - Frenchman P. Laplace or Englishman J. Michell? In 1973, the well-known English theoretical physicists S. Hawking and G. Ellis, in a book devoted to modern special mathematical problems of the structure of space and time, cited the work of French P. Laplace with a proof of the possibility of the existence of black stars; then the work of J. Michell was not yet known. In the autumn of 1984, the famous English astrophysicist M Rice, speaking at a conference in Toulouse, said that although it is not very convenient to speak in France, he must emphasize that the Englishman J. Michell was the first to predict invisible stars, and showed a snapshot of the first page of the corresponding work. This historic remark was met with both applause and smiles from those present.

How can one not recall the discussions between the French and the British about who predicted the position of the planet Neptune from disturbances in the movement of Uranus: the Frenchman U. Le Verrier or the Englishman J. Adams? As is known, both scientists independently correctly indicated the position new planet. Then the Frenchman U. Le Verrier was more fortunate. Such is the fate of many discoveries. Often they are done almost simultaneously and independently. different people Usually priority is given to those who have penetrated deeper into the essence of the problem, but sometimes these are just the vagaries of fortune.

But the prediction of P. Laplace and J. Michell was not yet a real prediction of a black hole. Why?

The fact is that at the time of P. Laplace it was not yet known that faster than light in nature, nothing can move. It is impossible to overtake the light in the void! This was established by Einstein in special theory relativity already in our century. Therefore, for P. Laplace, the star he considered was only black (non-luminous), and he could not know that such a star loses the ability to “communicate” with the outside world in any way, to “report” anything to distant worlds about the events taking place on it . In other words, he did not yet know that it was not only a "black", but also a "hole" into which one could fall, but impossible to get out. Now we know that if light cannot escape from some region of space, then nothing can escape at all, and we call such an object a black hole.

Another reason why P. Laplace's reasoning cannot be considered rigorous is that he considered gravitational fields of enormous force, in which falling bodies are accelerated to the speed of light, and the outgoing light itself can be delayed, and applied the law of gravity Newton.

A. Einstein showed that Newton's theory of gravitation is inapplicable for such fields, and created new theory, valid for superpowers, as well as for rapidly changing fields (for which the Newtonian theory is also inapplicable!), and. called it the general theory of relativity. It is the conclusions of this theory that must be used to prove the possibility of the existence of black holes and to study their properties.

General theory Relativity is an amazing theory. It is so deep and slender that it evokes a feeling of aesthetic pleasure in anyone who gets to know her. Soviet physicists L. Landau and E. Lifshitz in their textbook "Field Theory" called it "the most beautiful of all existing physical theories." German physicist Max Born said about the discovery of the theory of relativity: "I admire him as a work of art." BUT Soviet physicist V. Ginzburg wrote that it evokes “... a feeling ... akin to that experienced by looking at the most outstanding masterpieces of painting, sculpture or architecture.”

Numerous attempts at a popular presentation of Einstein's theory can, of course, give a general impression of it. But, frankly, it is as little like the delight of knowing the theory itself as getting to know a reproduction. Sistine Madonna” differs from the experience that arises when considering the original, created by the genius of Raphael.

And yet, when there is no possibility of admiring the original, you can (and should!) get acquainted with the available reproductions, better than the good ones (and there are all sorts).

Novikov I.D.

Black holes - perhaps the most mysterious and enigmatic astronomical objects in our Universe, have attracted the attention of pundits and excite the imagination of science fiction writers since their discovery. What are black holes and what do they look like? Black holes are extinguished stars, due to their physical characteristics, possessing such high density and gravity so powerful that not even light can escape.

The history of the discovery of black holes

For the first time, the theoretical existence of black holes, long before their actual discovery, was suggested by someone D. Michel (an English priest from Yorkshire, who is fond of astronomy at his leisure) back in 1783. According to his calculations, if we take ours and compress it (in modern computer terms, archive it) to a radius of 3 km, such a large (just huge) gravitational force is formed that even light cannot leave it. This is how the concept of “black hole” appeared, although in fact it is not black at all, in our opinion, the term “dark hole” would be more appropriate, because it is precisely the absence of light that takes place.

Later, in 1918, the great scientist Albert Einstein. But only in 1967, through the efforts of the American astrophysicist John Wheeler, the concept of black holes finally won a place in academic circles.

Be that as it may, both D. Michel, and Albert Einstein, and John Wheeler in their works assumed only the theoretical existence of these mysterious celestial objects in outer space, however, the true discovery of black holes took place in 1971, it was then that they were first noticed in space. telescope.

This is what a black hole looks like.

How do black holes form in space?

As we know from astrophysics, all stars (including our Sun) have some limited amount of fuel. And although the life of a star can last for billions of years, sooner or later this conditional supply of fuel comes to an end, and the star “goes out”. The process of "extinction" of a star is accompanied by intense reactions, during which the star undergoes a significant transformation and, depending on its size, can turn into a white dwarf, a neutron star, or a black hole. Moreover, the largest stars, which have incredibly impressive dimensions, usually turn into a black hole - due to the compression of these most incredible sizes, a multiple increase in the mass and gravitational force of the newly formed black hole occurs, which turns into a kind of galactic vacuum cleaner - absorbs everything and everything around it.

A black hole swallows a star.

A small note - our Sun, by galactic standards, is not at all a large star, and after fading, which will occur in about a few billion years, most likely it will not turn into a black hole.

But let's be honest with you - today, scientists still do not know all the intricacies of the formation of a black hole, undoubtedly, this is an extremely complex astrophysical process, which in itself can last millions of years. Although it is possible to move in this direction, the detection and subsequent study of the so-called intermediate black holes, that is, stars that are in a state of extinction, in which an active process of black hole formation is taking place, could be made. By the way, a similar star was discovered by astronomers in 2014 in the arm of a spiral galaxy.

How many black holes exist in the universe

According to the theories of modern scientists, there may be up to hundreds of millions of black holes in our Milky Way galaxy. There can be no less of them in the galaxy next to us, to which there is nothing to fly from our Milky Way - 2.5 million light years.

Theory of black holes

Despite the huge mass (which is hundreds of thousands of times greater than the mass of our Sun) and the incredible strength of gravity, it was not easy to see black holes through a telescope, because they do not emit light at all. Scientists managed to notice a black hole only at the moment of its "meal" - the absorption of another star, at this moment a characteristic radiation appears, which can already be observed. Thus, the black hole theory has found actual confirmation.

Properties of black holes

The main property of a black hole is its incredible gravitational fields, which do not allow the surrounding space and time to remain in their usual state. Yes, you heard right, time inside a black hole flows many times slower than usual, and if you were there, then returning back (if you were so lucky, of course) you would be surprised to notice that centuries have passed on Earth, and you won’t even grow old have time. Although let's be truthful, if you were inside a black hole, you would hardly have survived, since the gravitational force there is such that any material object would simply be torn apart, not even into parts, into atoms.

But if you were even close to a black hole, within the limits of its gravitational field, then you would also have a hard time, because the more you resisted its gravity, trying to fly away, the faster you would fall into it. The reason for this seemingly paradox is the gravitational vortex field, which all black holes possess.

What if a person falls into a black hole

Evaporation of black holes

English astronomer S. Hawking discovered interesting fact: black holes also happen to emit . True, this applies only to holes of relatively small mass. The powerful gravity around them creates pairs of particles and antiparticles, one of the pair is pulled inward by the hole, and the second is ejected outward. Thus, a black hole radiates hard antiparticles and gamma rays. This evaporation or radiation from a black hole was named after the scientist who discovered it - "Hawking radiation".

The biggest black hole

According to the theory of black holes, in the center of almost all galaxies there are huge black holes with masses from several million to several billion solar masses. And relatively recently, scientists have discovered the two largest black holes known to date, they are in two nearby galaxies: NGC 3842 and NGC 4849.

NGC 3842 is the brightest galaxy in the constellation Leo, located at a distance of 320 million light-years from us. In the center of it there is a huge black hole with a mass of 9.7 billion solar masses.

NGC 4849 is a galaxy in the Coma cluster, 335 million light-years away, boasting an equally impressive black hole.

The zones of action of the gravitational field of these giant black holes, or in academic terms, their event horizon, is about 5 times the distance from the Sun to! Such a black hole would eat our solar system and wouldn't even flinch.

The smallest black hole

But there are very small representatives in the vast family of black holes. So the most dwarf black hole discovered by scientists at the moment in its mass is only 3 times the mass of our Sun. In fact, this is the theoretical minimum necessary for the formation of a black hole, if that star were a little smaller, the hole would not have formed.

Black holes are cannibals

Yes, there is such a phenomenon, as we wrote above, black holes are a kind of "galactic vacuum cleaners" that absorb everything around them, including ... other black holes. Recently, astronomers have discovered that a black hole from one galaxy is being eaten by another large black glutton from another galaxy.

• According to the hypotheses of some scientists, black holes are not only galactic vacuum cleaners that suck everything into themselves, but under certain circumstances they themselves can generate new universes.
• Black holes can evaporate over time. We wrote above that it was discovered by the English scientist Stephen Hawking that black holes have the property of radiation and after some very long period of time, when there is nothing to absorb around, the black hole will begin to evaporate more, until eventually it gives up all its mass into surrounding space. Although this is only an assumption, a hypothesis.
• Black holes slow down time and bend space. We have already written about time dilation, but space in the conditions of a black hole will be completely curved.
• Black holes limit the number of stars in the universe. Namely, their gravitational fields prevent the cooling of gas clouds in space, from which, as you know, new stars are born.

Black holes on the Discovery Channel, video

And in conclusion, we offer you an interesting scientific documentary about black holes from the Discovery channel.

When writing the article, I tried to make it as interesting, useful and of high quality as possible. I would be grateful for any feedback and constructive criticism in the form of comments on the article. You can also write your wish / question / suggestion to my mail [email protected] or on Facebook, with respect, the author.

Due to the relatively recent rise in interest in making popular science films about space exploration, the modern viewer has heard a lot about such phenomena as the singularity, or black hole. However, films, obviously, do not reveal the full nature of these phenomena, and sometimes even distort the constructed scientific theories for more efficiency. For this reason, the presentation of many modern people about these phenomena either completely superficially, or completely erroneously. One of the solutions to the problem 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 hypothetical massive body that has such a strong gravitational attraction that the second cosmic velocity for it would exceed the speed of light. The second escape velocity is the speed that a relatively small object would need to overcome the gravitational pull celestial body and go beyond the closed orbit around this body. According to his calculations, a body with the density of the Sun and with a radius of 500 solar radii will have a second cosmic speed equal to the speed of light. In this case, even the light will not leave the surface of such a body, and therefore this body will only absorb the incoming light and remain invisible to the observer - a kind of black spot against the background of dark space.

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

Einstein's equation

As a result of applying general relativity to black holes and solving the Einstein equations, the main parameters of a black hole were revealed, of which there are only three: mass, electric charge and angular momentum. It should be noted the significant contribution of the Indian astrophysicist Subramanyan Chandrasekhar, who created a fundamental monograph: “ mathematical theory black holes."

Thus, the solution of the Einstein equations is represented by four options for four possible types of black holes:

• Black hole without rotation and without charge - Schwarzschild's 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 you to calculate the external gravitational field of a spherical massive body. A feature of the German scientist's concept of black holes is the presence of an event horizon and the one behind it. Schwarzschild also first calculated 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.
• A black hole without rotation with a charge - the 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.
• A black hole with rotation and no charge - Kerr's solution (1963). A rotating Kerr black hole differs from a static one by the presence of the so-called ergosphere (read on 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 BH parameters. However, it is still assumed that black holes in nature have an insignificant charge.

The formation of a black hole

There are several theories about how a black hole is formed and appears, the most famous of which is the emergence of a star with sufficient mass as a result of gravitational collapse. 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 shrink into a superdense one. If the pressure of the gas of a neutron star cannot compensate for the gravitational forces, that is, the mass of the star overcomes the so-called. Oppenheimer-Volkov limit, then the collapse continues, as a result of which matter is 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 that is at the stage of transformation into a galaxy or some kind of cluster. In the case of insufficient internal pressure to compensate for the same gravitational forces, a black hole can arise.

Two other scenarios remain hypothetical:

• The occurrence of a black hole as a result - the so-called. primordial black holes.
• Occurrence as a result of nuclear reactions at high energies. An example of such reactions is experiments on 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 a 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 of the existing physical theories do not work inside it. Thus, the physics of the singularity remains a mystery to scientists today. black hole - this is a kind of border, crossing which, a physical object loses the ability to return back beyond it and unequivocally "fall" into the singularity of a black hole.

The structure of a black hole becomes somewhat more complicated in the case of the Kerr solution, namely, in the presence of BH rotation. Kerr's solution implies that the hole has an ergosphere. Ergosphere - a certain area 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 a kind of analogue of an accretion disk, which represents a rotating substance 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 greatest theoretical material on the appearance 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 BH mass is 2.5 - 3 solar masses. The heaviest black hole ever discovered (in the galaxy NGC 4889) has a mass of 21 billion solar masses. However, one should not forget about black holes, hypothetically resulting from 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 , namely 2 10 −5 g.
• Black hole size. The minimum BH radius 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, is about 2.95 km, then the minimum radius of a BH of 3 solar masses will be about nine kilometers. Such relatively small sizes do not fit in the head when it comes to massive objects that attract everything around. 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 of the detected BHs have masses greater than 105 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 the density of air. Based on these calculations, it is logical to assume that the formation of a black hole occurs not due to the 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 is also inversely proportional to its mass. This temperature is directly related to . The spectrum of this radiation coincides with the spectrum of a completely black body, that is, a body that absorbs all incident radiation. The radiation spectrum of a black body depends only on its temperature, then the temperature of a black hole can be determined from the Hawking radiation spectrum. As mentioned above, this radiation is the 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 BHs is so low that it does not allow one to detect the indicated radiation. 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 min.), Such BHs can emit energy of the order of ten million atomic bombs. But, fortunately, the creation of such hypothetical objects will 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 is a CHD made of?

Another question worries both scientists and those who are simply fond of astrophysics - what does a black hole consist of? There is no single answer to this question, since it is not possible to look beyond the event horizon surrounding any black hole. In addition, as mentioned earlier, the 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 which now revolve around it - various kinds of cosmic bodies and cosmic gas. The event horizon is just a thin implicit border, 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 emergence 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. In simple words: When a star collapses, its atoms are compressed in such a way that electrons combine with protons, thereby forming neutrons. Such a reaction does indeed take place in nature, with the formation of a neutron, neutrino emission occurs. However, these are just guesses.

What happens if you fall into a black hole?

Falling into an astrophysical black hole leads to stretching of the body. Consider a hypothetical suicide astronaut heading into a black hole wearing nothing but a space suit, 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) where the 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 subjected to a noticeably greater gravitational effect than, for example, the head. Then, due to gravity, or rather, tidal forces, the legs will “fall” faster. Thus, the body begins to gradually stretch 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 what a person will feel in this situation. It is worth noting that the effect of stretching the body is inversely proportional to the mass of the black hole. That is, if a BH with the mass of three Suns instantly stretches/breaks the body, then the supermassive black hole will have lower tidal forces and, there are suggestions that some physical materials could “tolerate” such a deformation without losing their structure.

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

It is noteworthy that for an observer outside, all bodies that have flown up to the event horizon will remain at the edge of this horizon until their image disappears. The reason for this phenomenon is the gravitational redshift. Simplifying somewhat, we can say that the light falling on the body of a suicide astronaut "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 the low-frequency - red. A shift of light along the spectrum will take place, as the suicide astronaut moves further and further away from the observer, albeit 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 only be detected in the infrared region, later in the radio frequency region, and as a result, the radiation will be completely elusive.

Despite what has been written 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 spaceship 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 such phenomena as wormholes and black holes.

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

The Einstein-Rosen Bridge is considered an impenetrable wormhole, as it is small and unstable.

passable wormhole possibly within the framework of the theory of black and white holes. Where the white hole is the output of the information that fell into the black hole. The white hole is described in the framework of general relativity, but today it remains hypothetical and has not been discovered. Another model wormhole proposed by American scientists Kip Thorne and his graduate student Mike Morris, which can be passable. However, as in the case of the Morris-Thorne wormhole, so 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, one should take into account the dimensions 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.
• Black holes medium weight . A conditional intermediate type of black holes that have increased due to the absorption of nearby objects, such as a gas accumulation, a neighboring star (in systems of two stars) and others space bodies.
• Supermassive black hole. Compact objects with 10 5 -10 10 solar masses. Distinctive properties of such BHs are paradoxically low density, as well as weak tidal forces, which were discussed earlier. It is this supermassive black hole at the center of our Milky Way galaxy (Sagittarius A*, Sgr A*), as well as most other galaxies.

Candidates for CHD

The nearest black hole, or rather a candidate for the role of a black hole, is an object (V616 Unicorn), 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 solar mass, as well as an invisible small body, the mass of which is 3 - 5 solar masses. If this object turns out to be a small black hole of stellar mass, then by right it will be the nearest black hole.

Following this object, the second closest black hole is Cyg 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 star system V4641 Sagittarii (V4641 Sgr), estimated in 1999 to be 1600 light-years away. However, subsequent studies increased this distance by at least 15 times.

How many black holes are in our galaxy?

There is no exact answer to this question, since it is rather difficult to observe them, and during the entire study of the sky, scientists managed to detect about a dozen black holes within Milky Way. Without indulging in calculations, we note that in our galaxy there are about 100 - 400 billion stars, and about 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 register huge black holes, it is logical to assume that most of the BHs 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) orbiting 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 huge mass (100,000 solar masses), scientists suggest 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 biggest black hole

The largest black hole in the universe that scientists have been able to detect is a supermassive black hole, the FSRQ blazar, at the center of the galaxy S5 0014+81, at a distance of 1.2·10 10 light-years from Earth. According to preliminary results of observation, 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 big bang). If this giant black hole does not absorb the matter surrounding it, then it will live to see the era of black holes - one of the eras in 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, then it will become one of the last black holes that will exist in the Universe.

The other two known black holes, though not named, have highest value for the study of black holes, since they confirmed their existence experimentally, and also gave important results for the study of gravity. We are talking about the event GW150914, which is called the collision of two black holes into one. This event allowed to register .

Detection of black holes

Before considering methods for detecting black holes, one should answer the question - why is a black hole black? - the answer to it does not require deep knowledge in astrophysics and cosmology. The fact is that a black hole absorbs all the radiation falling on it and does not radiate at all, if you do not take into account the hypothetical. If we consider this phenomenon in more detail, we can assume that there are no processes inside black holes that lead to the release of energy in the form of electromagnetic radiation. Then if the black hole radiates, then it is 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 a completely low temperature of black holes.

Another generally accepted theory says that electromagnetic radiation is not at all capable of leaving the event horizon. It is most likely that photons (light particles) are not attracted by massive objects, since according to the theory they themselves have no mass. However, the black hole still "attracts" the 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 the "pit", which does not even have a "bottom".

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

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

Detection methods

Consider 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 some accumulations of cosmic bodies and gas, which are among the brightest astronomical objects in the Universe. Since they have a high intensity of luminescence at relatively small sizes, there is reason to believe that the center of these objects is a supermassive black hole, which attracts the surrounding matter to itself. Due to such a powerful gravitational attraction, the attracted matter is so heated that it radiates intensely. The detection of such objects is usually compared with the detection of a black hole. Sometimes quasars can radiate jets of heated plasma in two directions - relativistic jets. The reasons for the emergence of such jets (jet) are not completely 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 a direct black hole.

A jet in the M87 galaxy hitting from the center of a black hole

Summing up the above, one can imagine, up close: it is a spherical black object, around which strongly heated matter rotates, forming a luminous accretion disk.

Merging and colliding 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 clearest example is the previously mentioned event called GW150914, when two black holes approached so much that, as a result of mutual gravitational attraction, they merged into one. An important consequence of this collision was the emergence of gravitational waves.

According to the definition of gravitational waves, these are changes in the gravitational field that propagate in a wave-like manner from massive moving objects. When two such objects approach each other, they begin to rotate around a common center of gravity. As they approach each other, their rotation around their own axis increases. Such variable oscillations of the gravitational field at some point can form one powerful gravitational wave that can propagate in space for millions of light years. So, at a distance of 1.3 billion light years, a collision of two black holes occurred, which formed 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 her definition, nothing can leave the black hole if it has crossed its event horizon. It is known that for the first time the Soviet theoretical physicist Vladimir Gribov mentioned the possibility of emission of particles by a black hole in his discussion with another Soviet scientist Yakov Zel'dovich. He argued that from the point of view of quantum mechanics, a black hole is capable of emitting particles through a tunnel effect. Later, with the help of quantum mechanics, he built his own, somewhat different theory, the English theoretical physicist Stephen Hawking. You can read more about this phenomenon. In short, in vacuum there are so-called virtual particles that are constantly born in pairs and annihilate each other, while not interacting with the outside world. But if such pairs arise at the black hole's event horizon, then strong gravity is hypothetically able to separate them, with one particle falling into the black hole, and the other going away from the black hole. And since a particle that has flown away from a hole can be observed, and therefore has positive energy, a particle that has fallen into a hole must have negative energy. Thus, the black hole will lose its energy and there will be an effect called black hole evaporation.

According to the available models of a black hole, as mentioned earlier, as its mass decreases, its radiation becomes more intense. Then, at the final stage of the existence of a black hole, when it may be reduced to the size of a quantum black hole, it will release a huge amount of energy in the form of radiation, which can 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, whose mass is on the order of 10 12 kg, should have evaporated and exploded around our time. Be that as it may, such explosions have never been seen by astronomers.

Despite Hawking's proposed mechanism for the destruction of black holes, the properties of Hawking's radiation cause a paradox in quantum mechanics. If a black hole absorbs some 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 the absorption of 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 real solution to this paradox has never been found. Known options for solving the paradox:

• Inconsistency of Hawking's theory. This entails the impossibility of destroying the black hole and its constant growth.
• The presence of white holes. In this case, the absorbed information does not disappear, but is simply thrown into another Universe.
• 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 not known to scientists.

• In 1970, an English scientist formulated the so-called. "principle of cosmic censorship" - "Nature abhors the bare singularity." This means that the singularity is formed only in places hidden from view, 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 occur.
• 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 has 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 nature of black holes:

• Black holes 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 a 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 occurs not due to the compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume.
• Time for bodies absorbed by black holes goes much slower than for an external observer. In addition, the absorbed bodies are significantly stretched inside the black hole, which has been called spaghettification by scientists.
• 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.