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 greater effect. For this reason, the idea of ​​many modern people about these phenomena is either completely superficial or completely erroneous. One of the solutions to the problem that has arisen is this article, in which we will try to understand the existing research results and answer the question - what is a black hole?

In 1784, the English priest and naturalist John Michell first mentioned in a letter to the Royal Society a 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 cosmic velocity is the speed that a relatively small object will need to overcome the gravitational attraction of a celestial body and go beyond the limits of a 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 on its surface a second cosmic velocity 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 Einstein's 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: "The Mathematical Theory of Black Holes".

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

• A black hole without rotation and without a charge is the Schwarzschild solution. One of the first descriptions of a black hole (1916) using Einstein's equations, but without taking into account two of the three parameters of the body. The solution of the German physicist Karl Schwarzschild allows 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 is 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 more about this and other components of a black hole).
• BH with rotation and charge - Kerr-Newman solution. This solution was calculated in 1965 and is currently the most complete, since it takes into account all three 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, causing matter to shrink 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. of a black hole is a certain boundary, crossing which, a physical object loses the ability to return back beyond its limits and unambiguously “falls” 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 largest 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 dimensions do not fit in the head when we are talking about 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 of 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 black holes 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 occurrence of a black hole as a result of the compression of a star to a neutron star with its subsequent compression, then, probably, the main part of the black hole consists of neutrons, of which the neutron star itself consists. In simple 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 how 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, but 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 such a case, the falling spacecraft would retain its structure. A reasonable question arises - where does the black hole lead? This question can be answered by the work of some scientists, linking two 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.

A traversable wormhole is possible within the theory of black and white holes. Where the white hole is the output of 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 of a wormhole was proposed by American scientists Kip Thorne and his graduate student Mike Morris, which can be passable. However, as in the case of the Morris-Thorn wormhole, as well as 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.
• Intermediate mass black holes. A conditional intermediate type of black holes that have increased due to the absorption of nearby objects, such as gas accumulations, a neighboring star (in systems of two stars) and other cosmic 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 the star system V4641 Sagittarii (V4641 Sgr), which, according to estimates in 1999, was located at a distance of 1600 light years. However, subsequent studies 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 the 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 the 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, although not named, are of the greatest importance for the study of black holes, as 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 (particles of light) are not attracted by massive objects, since, according to the theory, they themselves have no mass. However, the black hole still "attracts" 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 the 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, if we take into account the effect of gravitational redshift, it is possible that light in a black hole loses its frequency, shifting along the spectrum 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 clusters 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 emit 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 BH 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 Zeldovich. 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, there are so-called virtual particles in vacuum, which are constantly born in pairs and annihilate each other, while not interacting with the surrounding 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, the mass of which 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 the mechanism proposed by Hawking for the destruction of black holes, the properties of Hawking radiation cause a paradox in the framework of 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 out 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

Summing up the above, we can highlight several interesting and unusual features of the 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 black holes 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.

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 at 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 the attraction of a 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".

Nowadays. 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 will provide great opportunities for new discoveries of black hole features.

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 join the accretion disk around Sagittarius A*, generating shock waves in it. 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 of 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.

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 a huge mass run out of nuclear fuel. Nuclear reactions stop and the stars begin to cool down. The body of a star shrinks under the influence of gravity and gradually it begins to attract smaller objects towards itself, transforming into a black hole.

First studies

The luminaries of science began to study black holes not so long ago, despite the fact that the basic concepts of their existence were developed 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.

Black hole borders

The first of the boundaries of a black hole is called the static limit. This is the boundary of the region, falling into which a foreign object can no longer be at rest and begins to rotate relative to the black hole in order to keep from falling into it. The second boundary is called the event horizon. Everything inside the black hole once passed its outer boundary and moved towards the point of singularity. According to scientists, here the substance flows into this central point, the density of which tends to the value of infinity. People cannot know what laws of physics operate inside objects with such a 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 the knowledge of mankind about the world around us.

The structure of black holes

The event horizon is the impregnable boundary of a black hole. Inside this border there is a zone that even objects whose speed of movement is equal to the speed of light cannot leave. Even quanta of light itself cannot leave the event horizon. Being at this point, no object can escape from the black hole. By definition, we cannot know what is inside a black hole - after all, in its depths there is a so-called singularity point, which is formed due to the ultimate compression of matter. Once an object enters the event horizon, from that point on it can never break out of it again and become visible to observers. On the other hand, those who are inside black holes cannot see anything that is 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 also be twice as large. If scientists could find a way to turn the Earth into a black hole, the event horizon would be only 2 cm across.

Main categories

As a rule, the mass of average black holes 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 heavenly bodies. Black holes of ordinary mass appear after the completion of the life cycle of large stars. 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 closely adjacent stars. However, these are only guesses, not confirmed by facts.

What's inside a black hole: conjectures

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

There is another concept, according to which there is a white hole at the opposite end of such a tunnel, from where a gigantic amount of energy comes from our Universe to another world through black holes. However, on this stage development of science and technology about 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, you can define the concept of the 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 remoteness 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 view is now generally accepted in scientific circles. Studies that have been carried out over the past 50 years have not only confirmed this hypothesis, but also led scientists to the conclusion that there are black holes in 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, greatly complicates the life of modern scientists - because of this discovery, many difficulties have appeared in the theory of black holes. In classical physics there is the concept of vacuum. This word denotes complete emptiness and the absence of matter. However, with the development of quantum physics, the concept of vacuum has been 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 found 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 the black hole, and the particle flies away. As a result, scientists observe some radiation around these space objects. It is called Hawking radiation.

During this radiation, the matter inside the black hole slowly evaporates. The hole loses mass, while the radiation intensity 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 a 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 lifetime of our Universe by 65 orders of magnitude.

The question of 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 the black hole evaporates completely? Both theories - both quantum physics and classical - deal with the description of the state of the system. Having information about the initial state of the system, with the help of the 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 conservation 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 lies in the fact that, by definition, the transmission of information 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 drag him in the direction of itself. Eventually, the person would stretch out so much that they would become a stream of subatomic particles moving towards the point of singularity. Of course, it is impossible to prove this hypothesis, because scientists are unlikely to ever know what happens inside black holes. Now some physicists say that if a person fell into a black hole, then he would have a clone. The first of his 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.

Issue 39

In a new astronomy video lesson, the professor will talk about how black holes form and why they are dangerous.

How black holes are formed

Black holes cannot be touched and cannot be walked on. Black holes are called areas in space-time, which form a super-powerful attraction. Gravity bends space and time, which means that there are no straight lines inside a black hole, space is crumpled and intertwined. If a star forms next to a black hole, then the gravitational forces of the black hole will tear the star apart and it will disappear into the bowels of the hole. If something falls into a black hole, it stays there forever. To overcome the powerful attraction of a black hole, it is necessary to develop a speed greater than the speed of light, but this, alas, is impossible. Scientists do not know exactly how supermassive black holes form, but with ordinary black holes everything is more or less clear. In the process of evolution of a star, hydrogen gradually burns out, accordingly, its amount decreases, which leads to the fact that the force of light pressure begins to exceed the force of gravitational compression. The star greatly increases in size and turns into a red giant, which subsequently explodes. After the explosion, compression begins, then the star cools down and it becomes not directly visible. But, if the mass of the remnant of the red giant exceeds the solar mass by 2-2.5 times, then its compression cannot stop, since the gravitational force completely suppresses the resistance to compression, as a result, this remnant is compressed into a dense tiny body, as if closed in itself. And it is at this moment of gravitational collapse (compression) that black holes are formed. As a result, it turns out that the mass is concentrated in such a small area that even the speed of light is not enough to leave its vicinity. Hence the first part of the name is black, since it is able to absorb even light. The second part - a hole - means that everything that falls into the region of a black hole becomes forever inaccessible to observation.

« Black holes » Universe.

"Black Hole"

What's new in space? Black holes? Not only astronomers, but also those who are interested in the life of the universe, including curious schoolchildren, are not averse to looking into them,” said E. Levitan, Doctor of Pedagogical Sciences.

In popular scientific literature, in articles about the Universe, one can often come across the term "black hole". When you read this phrase for the first time, you immediately have an image of, say, a hole in the wall. The mention of holes in the universes, originally also associated with a hole in the sky. So what is a black hole?

Black hole - it is a cosmic object of incredible density, with absolute gravity, such that any cosmic body, and even space and time itself, is absorbed by it, this is a kind of end point of everything.

"Black Hole" they are a bit like a vacuum cleaner that works in space, but unlike a vacuum cleaner, black holes do not suck in all the objects in their zone of influence, but, using their gravity, only attract everything around. This is called the vacuum effect (lack of air), which you can observe at home in your room. When the vacuum cleaner is turned on while cleaning the room, you can observe how crumbs, dirt and small objects begin to move towards the vacuum cleaner. The suction force of a black hole is not as great as that of a vacuum cleaner, so space objects are not sucked into it, but only attracted.

What does a black hole do? Black holes govern the very evolution of the universe. They are in a central place, but they cannot be seen, their signs can be detected, although black holes have the property of destroying, they also help to build galaxies.

How is a black hole born? When a big star runs out of fuel, it can no longer support its weight. Pressure from massive layers of hydrogen causes the star to shrink less and less. Eventually, the star will become smaller than an atom. Imagine for a moment that the entire star is crushed into a point, smaller than an atom.

How can something be smaller, but keep the same amount of mass? In fact, everything is very simple. Take a sponge, the size of a bottle, we can easily crush it in our hands. But here's an interesting point. If we do something smaller by squeezing it, its gravity becomes stronger. Imagine if we compress a star into the size of an atom, how powerful will its gravity become? Gravity black The hole is so powerful that it absorbs everything, even light that comes too close. Quite right, even light cannot escape a black hole.

The structure of a black hole: Black holes are made up of three main parts.) The outer layer of a black hole is called the outer event horizon. Inside the outer event horizon, you can still escape the black hole's gravity because gravity isn't as strong here. The middle layer of a black hole is called the inner event horizon. The center of a black hole is called the Singularity. This strange word means a crushed star. The Singularity is where the black hole's gravity is strongest.

What happens if you get into it? It's very interesting here. For an observer from the Earth, it will be seen how the one who flew to the black hole instantly fell into it and disappeared. And the one who will fly up to it will slowly approach, the clock will go slower and slower, everything will slow down (this happens because the black hole bends (violates) the space (world) around it.

What do scientists think about black holes? Some scientists believe that black holes are gateways to parallel universes, which may well be the case.

Now it is clear that a black hole is a completely mysterious phenomenon in the Cosmos, about which humanity knows practically nothing. Therefore, any new information about them becomes a sensation. And since the study of black holes is almost impossible in space, their analogues and create models.

Analogues of "black holes" on Earth .

- bodies of such huge proportions that it is difficult for a person to realize them. But on Earth, it turns out, there is a "miniature" analogue of these . And these analogues have recently been discovered in the South Atlantic Ocean.

An analogue of a space monster was created in a Chinese laboratory - it is able to suck in light.

"Black holes" will make it possible to create solar batteries of a new generation, capable of capturing the energy of the star much more efficiently than the current ones.

Black hole models.

Combining the knowledge of the world's leading physicists about the black hole with cutting-edge visual effects, the movie Interstellar showed the most accurate black hole model in the history of science fiction. The world's leading scientists have proposed the use of Hollywood sci-fi film "Interstellar" as a teaching aid for children on black holes

The scientists conducted experiments by simulating "in the bathroom" black holes with their event horizon.

Ripples in the stream behaves in much the same way as light waves in space-time. Near the stone, the flow becomes non-uniform, the ripples bend, and the wavelengths change. The same thing happens with light in the gravitational fields of stars and planets. In some cases, the flow is so fast that the ripples cannot propagate against the current, like light unable to escape from a black hole.

What do a drop of water, a black hole and an atom have in common? A group of British scientists headed by Prof. turned to a drop of water because the surface tension forces that hold it intact can be used as an analogue of other forces acting in other objects, from an atom to a black hole.

Another interesting model of a "black hole" was created in Novosibirsk planetarium. One of the fun games for kids. It is very interesting to compare how fast and how heavy and light balls are drawn into the hole. Lasts the longest, naturally, heavy.

How to visually show and present a “black hole”?

How can one visually show and imagine a “black hole” so that it is easier for us to understand its structure.

Imagine a black hole as a waterfall, gravity as a river flowing towards the waterfall, and a beam of light as a kayak. Above the waterfall, the current is weak, a person in a boat can row against the current and get out. But the closer to the waterfall, the stronger the current and the more difficult it is to get out. The edge of the waterfall is the edge of the black hole. Despite all the strength of the man in the boat, he falls. The same is true in space.

For a visual representation of the "Black Hole", let's take a large piece of cling film, stretch it in our hands and put a small ball in the center so that it forms a deflection due to its weight. Let's put a few drops of water on the sheet and see how they roll down the film right to the ball. This will show how gravity works. Let's remove the ball and touch the film with your finger and determine - the more you pull it off (the heavier the object), the stronger the funnel. Then we make a hole in the middle of the film, which represents a very, very heavy object. Drops of water will slip through this hole. It turns out that a black hole is such a heavy object that it bends space. Everything that gets into it (like drops) never comes back."