Black hole in space: where does it come from. What are black holes and how do they form?

It received this name due to the fact that it absorbs light, but does not reflect it like other objects. In fact, there are many facts about black holes, and today we will talk about some of the most interesting ones. Until relatively recently, it was believed that black hole in space sucks in everything that is near it or flies by: the planet is garbage, but recently scientists began to assert that after a while the contents “spit out” back, only in a completely different form. If you are interested black holes in space Interesting Facts we will talk about them in more detail today.

Is there a threat to the Earth?

There are two black holes that can pose a real threat to our planet, but they are, fortunately for us, far away at a distance of about 1600 light years. Scientists were able to detect these objects only because they were close to the Solar System and special X-ray devices were able to see them. There is an assumption that the huge force of gravity can affect black holes in such a way that they merge into one.

It is unlikely that any of his contemporaries will be able to catch the moment when these mysterious objects disappear. So slowly is the process of death of holes.

A black hole is a star in the past

How do black holes form in space?? Stars have an impressive supply of fusion fuel, which is why they glow so brightly. But all resources run out, and the star cools, gradually losing its glow and turning into a black dwarf. It is known that a process of compression occurs in a cooled star, as a result, it explodes, and its particles scatter over great distances in space, attracting neighboring objects, thereby increasing the size of the black hole.

The most interesting about black holes in space we have yet to study, but surprisingly, its density, despite its impressive size, can be equal to the density of air. This suggests that even the largest objects in space can have the same weight as air, that is, be incredibly light. Here How do black holes appear in space?.

Time in the black hole itself and near it flows very slowly, so objects flying nearby slow down their movement. The reason for everything is the huge force of gravity, even more amazing fact, all the processes occurring in the hole itself have an incredible speed. Suppose if we observe what does a black hole look like in space, being outside the boundaries of the all-consuming mass, it seems that everything stands still. However, as soon as the object got inside, it would be torn apart in an instant. Today we are shown What does a black hole look like in space? modeled by special programs.

Definition of a black hole?

Now we know Where do black holes come from in space?. But what else is special about them? To say that a black hole is a planet or a star is impossible a priori, because this body is neither gaseous nor solid. This is an object that can distort not only the width, length and height, but also the timeline. Which is completely defying physical laws. Scientists argue that time in the region of the horizon of a spatial unit can move forward and backward. What is in a black hole in space it is impossible to imagine, the light quanta falling there are multiplied several times by the mass of the singularity, this process increases the power of the gravitational force. Therefore, if you take a flashlight with you and go to a black hole, it will not glow. Singularity is the point at which everything tends to infinity.

The structure of a black hole is a singularity and an event horizon. Inside the singularity, physical theories completely lose their meaning, so it still remains a mystery to scientists. Crossing the boundary (event horizon), the physical object loses the ability to return. We know far from all about black holes in space, but interest in them does not fade away.

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 leave 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 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: “ mathematical theory black holes."

Thus, the solution of the Einstein equations is represented by four options for four possible types 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 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 BH radius is 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 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. For description similar 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 / tears 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 be caught only in the infrared region, later in the radio frequency, 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.

Einstein-Rosen Bridge - is considered an impenetrable wormhole, as it has small size and is 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 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-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 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 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, 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 (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 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 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 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 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, in a vacuum there are so-called virtual particles, which are constantly born in pairs and annihilate with 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 variants solutions to 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

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 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.

"Technique-youth" 1976 No. 4, pp. 44-48

One of the days of the conference "Man and Space" was devoted to cosmic bodies that fill our universe: particles, fields, stars, galaxies, clusters of galaxies...

We publish a review of reports on this topic made at the conference - the report of Academician Y. ZELDOVICH "Fields and particles in the universe", as well as three reports devoted to the study of the observed manifestations of the most unique objects in our universe - "black holes". These reports are presented by the heads of the Institute's sectors space research Academy of Sciences of the USSR, Doctors of Physical and Mathematical Sciences I. NOVIKOV and R. SYUNYAEV and Researcher of the State Astronomical Institute named after P.K. Sternberg, Candidate of Physical and Mathematical Sciences N. SHAKUROY.

For several decades, the astronomical world has been concerned about the problem of the existence of "black holes" in the universe - the most amazing objects predicted by physicists on the basis of A. Einstein's general theory of relativity. "Black holes" are material bodies compressed by their own gravity to such a size that neither light nor any other particles can leave the surface and go to infinity.

Everyone is well aware of the concept of the second cosmic velocity. This is the initial speed that needs to be given to the spacecraft (or any other object) on the surface of the Earth in order to overcome the gravitational forces of attraction and escape into outer space. Numerically, it is equal to 11.2 km/s.

Imagine now a hypothetical spacecraft starting from the surface of some star, such as our Sun. In order for it to be able to free itself from the "gravitational embrace" of the star, it will need a speed of hundreds of kilometers per second. In the general case, the second space velocity depends on the mass M and the radius R of the body and is determined by the well-known formula: (G - constant of gravitational interaction). Obviously, the smaller the radius R has a body of a given mass M, the stronger its gravitational field, the more value second cosmic speed.

As early as the end of the 17th century, the famous French scientist Pierre Simon Laplace in a sense predicted "black holes", asking the question: to what size should a body be compressed so that the speed of escape from its surface is equal to the speed of light c = 300,000 km / s? Substituting the value of the speed of light c = 300,000 km/s into the expression for the second cosmic velocity, we find the value of the radius

For the Earth, it is only 3 cm, for the Sun - 3 km. Thus, if with the help of some external influence it was possible to compress these bodies to a radius R g, then they would not radiate anything outward, since it would be necessary to give the particles an initial speed greater than the speed of light, but the latter, as we know today, is the maximum possible speed for material particles.

The true dimensions of the Earth and other planets. The Sun and other stars are thousands of times larger than the radius R g , and for a long time scientists assumed that the internal pressure forces of matter would not allow it to shrink to a critical radius. But in the 30s of our century, several physicists (one of them was academician L. Landau) showed that sufficiently massive stars at the end of their evolution should turn into "black holes", that is, shrink to such a size that the gravitational field blocks the radiation coming from their surface. The process of compression of massive stars is irreversible: no superpowerful repulsive forces between particles can prevent the compression of a star almost to R g . This process of irreversible catastrophic contraction is called gravitational collapse, and the critical radius R g is called gravitational radius body.

We know that Newtonian mechanics is not applicable when the speed of particles is comparable to the speed of light. In this case, use special theory relativity. And to describe strong gravitational fields and the motion of matter in them, instead of Newton's theory of gravitation, they also use general theory relativity, or, as it is also called, Einstein's relativistic theory of gravity. It turned out to be striking that the calculation of the gravitational radius in the exact relativistic theory of gravity led to the same value: which Laplace calculated more than a century and a half ago. But, according to Newton's theory, no matter how huge a mass of matter we take, it can always be in an equilibrium state. Although the concept of a gravitational radius exists for it, the dimensions of the body, according to Newton's theory, are always larger.

Not so in the exact relativistic theory. It turns out that if the mass of a substance exceeds a certain critical value, then after losing its thermal energy, it must collapse under the action of gravitational forces. This critical mass value is approximately 2-3 times the mass of our Sun (2-3 Ms).

In the universe, we observe billions of stars, both with a mass ten times less than the sun, and dozens of times more. Stars lose their thermal energy in the form of electromagnetic radiation from the surface. The greater the mass of a star, the greater the luminosity it has. Thus, a star with a mass ten times the mass of the Sun has ten thousand times the luminosity.

Long-term energy losses are compensated by thermonuclear fusion reactions occurring in the deep interiors of stars. But after the exhaustion of nuclear resources, the star begins to cool. Calculations show that stars like our Sun burn up their reserves after about 10 billion years 1 , and with a mass ten times greater - after 10 million years. After all, their luminosity is 10,000 times greater. With the onset of cooling, the star begins to contract under the influence of gravitational forces. Depending on the mass, compression leads to three different types objects (see Fig. 1). Stars with a mass of the order of the sun turn into white dwarfs - rather dense bodies (density 10 5 - 10 9 g / cm 3), having dimensions comparable to the radius of the Earth. The force of gravity in white dwarfs is balanced by the pressure of degenerate electrons, which is due to the quantum properties of the dense electron gas. For stars with a mass greater than 1.2 ms. the pressure of degenerate electrons is no longer able to counteract the growing force of gravity, and such stars continue to shrink further. If the value of the mass does not exceed 2-3 Ms, then its compression stops at the density of the atomic nucleus 10 14 -10 15 g/cm 3 . At such a density, the matter is almost completely converted into neutrons, and the force of gravity is balanced by the pressure of the degenerate neutron gas. Naturally, such objects were called neutron stars. The radius of a neutron star is only a few kilometers. The compression of the original star, which has a radius of millions of kilometers, to a size of ten kilometers occurs instantly (in the framework of the concepts of astrophysics, that is, at a free fall speed of about an hour), and a gigantic amount of energy is released in a short time. The outer parts of the star literally explode and fly apart at speeds of tens of thousands of kilometers per second. Most of the energy is radiated in the form electromagnetic waves, so that the luminosity of the star over several days becomes comparable to the total luminosity of all the stars in the Galaxy. Such an explosion is called a supernova explosion.

1 The age of the Sun today is 5 billion years.

Finally, if the star's mass exceeds three times the mass of the Sun, then no repulsive forces can stop the compression process, and it ends in a relativistic collapse with the formation of a "black hole".

But this does not mean that the resulting space objects will have proportional masses. Academician Ya. Zel'dovich dwelled on the reasons for these inconsistencies in detail in his report. Gravitational forces are characterized by a mass defect. States may arise when the gravitational mass defect reaches 30, 50 and even 99%.

Theoretical calculations provide several methods for the birth of a "black hole" (Fig. 2). First, a direct collapse of a massive star is possible, in which the brightness of the original star, perceived by a distant observer, will rapidly decrease. From purple, the star quickly turns red, then infrared, and then goes out altogether. Although it will still radiate energy, the gravitational field becomes so strong that the photon paths will wind back towards the collapsing star. The following path is also possible: the central parts of the star are compressed into a dense hot neutron core with a mass greater than the critical one, and then after a rapid cooling (over a time of the order of tens of seconds), the massive neutron star collapses further into a “black hole”. Such a two-step process leads to the explosion of the outer parts of the star, similar to the explosion of a supernova, with the formation of a normal neutron star. Finally, a “black hole” can form from a neutron star tens of millions of years after the supernova explosion, when the mass of the neutron star as a result of the fallout of the surrounding interstellar matter onto its surface exceeds a critical value.

Is it possible to observe these three types of end objects of stellar evolution: white dwarfs, neutron stars and "black holes"?

Historically, it turned out that white dwarfs were discovered long before the theory of stellar evolution was understood. They were observed as compact white stars with high surface temperatures. But where do they draw their energy from, because, according to the theory, there are no sources of nuclear energy in them? It turns out that they shine due to the reserves of thermal energy that they have left from the previous, hot stages of evolution. With their small surface area, these stars lose their energy very sparingly. They slowly cool down and in the order of hundreds of millions of years turn into black dwarfs, that is, they become cold and invisible.

Neutron stars are more fortunate. They were first discovered by theorists "on the tip of a pen", and almost 30 years after the prediction, they were discovered as sources of cosmic strictly periodic radiation - pulsars. (For this discovery, A. Hewish, the leader of the group of British astronomers who discovered the first pulsar, was awarded the Nobel Prize.) Pulsars are observed with pulse repetition periods from hundredths of a second for the youngest pulsars to several seconds for pulsars whose age is tens of millions of years. The periodicity of pulsars is associated with their rapid rotation around their own axis.

Imagine a spotlight on the surface of some rotating object. If you are in the path of a beam of light from such an object, you will see that the radiation from it will come in the form of separate pulses with a period equal to the rotation period of the object - this will be a rough, approximate, but fundamentally correct model of a pulsar. Why does radiation from the surface of a neutron star escape in a narrow cone of angles, like a beam of light from a searchlight? It turns out that due to a powerful magnetic field of 10 11 -10 12 gauss, a neutron star radiates energy only along the lines of force from the magnetic poles, which, as a result of rotation, leads to the phenomenon of a pulsar as a cosmic beacon. It is curious that the energy radiated into outer space is drawn from its rotational energy, and the period of rotation of the pulsar gradually increases. From time to time, this smooth growth of the period is superimposed by frequency failures, when the pulsar almost instantly reduces the value of the period. These failures are caused by the "starquake" of the neutron star. As the rotation slows down in the solid crust of a neutron star (see Fig. 3), mechanical stresses gradually accumulate, and when these stresses exceed the ultimate strength, a sudden release of energy and a restructuring of the solid crust occur - the pulsar instantly reduces its rotation period during such a restructuring.

How do black holes radiate?

The external gravitational field is all that remains of a star after it collapses and turns into a "black hole". All the richness of the external characteristics of a star is a magnetic field, chemical composition, radiation spectrum - disappears in the process of gravitational collapse. Imagine for a moment a fantastic situation when our Earth would be next to a "black hole" (Fig. 4). The Earth would not just start falling into the "black hole", tidal forces would begin to deform the Earth, pulling it into a blob before it was completely swallowed up by the "black hole".

A "black hole" without rotation is characterized only by the value of the gravitational radius R g , which limits the sphere in the vicinity of the "black hole", from under which no signals can come out. If the “black hole” also has an angular momentum, then an area called the ergosphere appears above the gravitational radius. Being in the ergosphere, the particle cannot remain at rest. During the decay of a particle, energy can be extracted from the ergosphere - one fragment falls into the "black hole", and the second flies away to infinity, taking with it the excess energy (see the figure on page 44).

The search for "black holes" in our galaxy is most promising in binary star systems. More than 50% of stars are part of binary systems. Let one of them turn into a "black hole". If the second is at a sufficiently safe distance, that is, tidal forces do not destroy it, but only slightly deform it, then such two stars will still rotate around a common center of gravity, but one of them will be invisible. Soviet scientists, Academician Ya. Zel'dovich and O. Guseinov, in 1965 suggested looking for "black holes" among those binary systems where the more massive component is invisible. Later studies have shown that if an optical star loses matter from its surface, then a luminous halo may appear around the "black hole". And now all the hopes of astronomers are connected with the study of the interaction of "black holes" with the matter that surrounds them.

The spherical fall of cold matter onto a "black hole" does not lead to a noticeable release of energy: the "black hole" does not have a surface, upon impact against which the substance would stop and highlight its energy. But, as academician Ya. Zeldovich and American astrophysicist E. Salpeter independently showed in 1964, if a "black hole" is "blown" by a directed gas flow, then a strong shock wave arises behind it, in which the gas heats up to tens of millions of degrees and begins to emit in the X-ray range of the spectrum. This happens when an optical star is outflowing with a stellar wind and its size is small compared to some critical cavity called the Roche lobe (Fig. 5a). If the star fills the entire Roche lobe, then the outflow occurs through the “narrow neck” (Fig. 56), and a disk forms around the “black hole”. The matter in the disk, as it loses speed, falls in a slowly twisting spiral towards the "black hole". In the process of falling, part of the gravitational energy is converted into heat and heats the disk. The areas of the disk close to the "black hole" are heated the most. The temperature in them rises to tens of millions of degrees, and as a result, the disk, as in the case of a shock wave, main part emits energy in the x-ray range.

A similar picture will be observed if instead of a "black hole" in a binary system there is a neutron star (Fig. 5c). However, a neutron star has a strong magnetic field. This field directs the incident matter to the region of the magnetic poles, where the main part of the energy is released in the X-ray range. When such a neutron star rotates, we will observe the phenomenon of an X-ray pulsar.

At present, a large number of compact X-ray sources have been discovered in binary systems. They were discovered by regularly turning off the radiation during the eclipse of the source by a neighboring optical star. If the radiation itself is additionally modulated, then it is most likely a neutron star, if not, there is reason to consider such a source as a "black hole". Estimates of their masses, which can be made on the basis of Kepler's laws, have shown that they are greater than the critical limit for a neutron star. The Cygnus X-1 source with a mass greater than 10 Ms has been studied in most detail. In all its characteristics, it is a "black hole".

For a long time, most astrophysicists believed that an isolated "black hole" without any particles around it did not radiate. But a few years ago, the famous English astrophysicist S. Hawking showed that even a completely isolated "black hole" should emit photons, neutrinos and other particles into outer space. This energy flow is caused by quantum phenomena of particle production in a strong alternating gravitational field. During the collapse, the star asymptotically approaches the value of the gravitational radius and reaches it only in an infinitely long time. In the void around the "black hole" there is always a small non-static field. And in non-static fields, new particles should be born. Hawking calculated in detail the process of emission of "black holes" and showed that over time, "black holes" decrease, they seem to be drawn in and reduced to arbitrarily small sizes. In accordance with the obtained formulas, the quantum radiation of a "black hole" is characterized by a temperature T ~ 10 -6 Ms/M°K. Thus, if the mass of the "black hole" is of the order of the sun, then the effective radiation temperature is negligible - 10 -6 °K. You can also calculate the lifetime of the "black hole": years. This time for "black holes" of stellar mass is colossally long, and the Hawking processes do not affect the observed manifestations of "black holes" in binary systems.

About ten years ago, the most amazing and still unsolved objects were discovered in the universe - quasars. The luminosity of quasars is hundreds of times higher than the luminosity of even very large galaxies, that is, quasars shine more strongly than hundreds of billions of stars. Along with the monstrously high luminosity, another amazing fact is observed - in a few years or even months, the radiation flux from quasars can change dozens of times. The variability of radiation indicates that it is produced in a very compact region with dimensions not more sizes solar system. This is very small for an object with a colossal luminosity. What are these bodies?

Several models have been proposed by theorists. One of them suggests the presence of a supermassive star with a mass 10 million times the mass of our Sun. Such a star radiates a lot of energy, but its lifetime is very short on a cosmic scale: only a few tens of thousands of years, after which it cools down and collapses into a “black hole”. In another model, it was assumed that the quasar is a cluster of tens of millions of hot massive stars (Fig. 6). Stars will collide, stick to one another, become more massive, evolve. In this case, supernova explosions will often occur and a colossal energy release will be observed. But even in this case, a close cluster of stars turns into a supermassive "black hole".

The English astrophysicist D. Linden-Lell was the first to think about how such a supermassive "black hole" could be detected. He showed that the fall of interstellar gas, which is always present in interstellar space around a supermassive "black hole", will lead to an enormous energy release. Around the "black hole" will appear a halo of radiation with all the properties observed in quasars. At present, a theory has been constructed of the emission of quasars as supermassive "black holes" into which matter falls, but unambiguous evidence for this model has not yet been obtained.

Review prepared by Candidate of Physical and Mathematical Sciences
NIKOLAY SHAKURA

Astronomers have discovered the most massive object in the entire universe at the moment. It turned out to be a superheavy black hole at the center of the galaxy NGC 1277 in the constellation Perseus, 228 million light-years away from Earth.
The discovery was made by a group of German scientists from the Institute of Astronomy in Heidelberg during analyzes of images of the galaxy obtained with the infrared spectrometer of the Hobby-Eberli telescope. A black hole in the constellation Perseus contains a huge amount of matter - from 14 to 20 billion masses of our Sun, Rossiyskaya Gazeta writes.
It turned out that this mass is more than 14 percent of the mass of the entire galaxy, while usually supermassive black holes include about 0.1 percent. Previously, the black hole in the galaxy NGC 4889, whose mass is 9.8 billion solar masses, was considered the heaviest object.
“This is indeed a very strange galaxy. It is almost entirely composed of a black hole. Maybe we have discovered the first object from the class of black hole galaxies,” said astronomer Karl Gebhardt, one of the authors of the study. According to scientists, the results of the study can change the theory of the formation and growth of black holes.
According to scientists, the results of the study can change the theory of the formation and growth of black holes, notes the BBC.
Astrophysicists believe that there is always at least one black hole at the center of most massive galaxies. The nature of the formation of these objects is not yet completely clear. Black holes are believed to be formed by unrestricted gravitational contraction, often after death. big stars. They create such a strong gravitational attraction that no substance, even light, can leave them, clarifies the Saboteur.
Another discovery was made by astronomers of the European Southern Observatory, writes ukrinform.ua. They discovered an object also associated with a black hole - a quasar. With its attraction, a black hole destroys stars flying by. The resulting stellar gas is gradually drawn into the hole, while simultaneously rotating. Compression and rapid rotation of the central part of the disk leads to its heating and powerful radiation. The black hole does not have time to absorb part of the matter, and it partially leaves it in the form of narrowly directed streams of gas and cosmic rays - this is called a quasar.
The found quasar is 5 times more powerful than those that scientists have previously observed. The rate of matter ejection from this quasar is two trillion times the radiation of the Sun, and 100 times the radiation of our entire galaxy. “I have been looking for such a monster for 10 years,” said one of the researchers, Professor Naum Arav.
It is noted that the quasar is located 1000 light years from a supermassive black hole, and moves at a speed of 8 thousand kilometers per second.

Black holes, dark matter, dark matter... These are undoubtedly the strangest and most mysterious objects in space. Their bizarre properties can defy the laws of physics in the universe and even the nature of existing reality. To understand what black holes are, scientists offer to “change landmarks”, learn to think outside the box and apply a little imagination. Black holes are formed from the cores of super massive stars, which can be described as a region of space where a huge mass is concentrated in the void, and nothing, not even light, can escape the gravitational attraction there. This is the area where the second space velocity exceeds the speed of light: And the more massive the object of motion, the faster it must move in order to get rid of its gravity. This is known as the second escape velocity.

The Collier Encyclopedia calls a black hole a region in space that has arisen as a result of a complete gravitational collapse of matter, in which the gravitational attraction is so strong that neither matter, nor light, nor other information carriers can leave it. That's why inner part a black hole is causally unrelated to the rest of the universe; physical processes occurring inside a black hole cannot affect processes outside it. A black hole is surrounded by a surface with the property of a unidirectional membrane: matter and radiation freely fall through it into the black hole, but nothing can escape from it. This surface is called the "event horizon".

Discovery history

Black holes, predicted by general relativity (the theory of gravity proposed by Einstein in 1915) and others, are more modern theories gravitation were mathematically substantiated by R. Oppenheimer and H. Snyder in 1939. But the properties of space and time in the vicinity of these objects turned out to be so unusual that astronomers and physicists did not take them seriously for 25 years. However, astronomical discoveries in the mid-1960s forced us to look at black holes as a possible physical reality. New discoveries and exploration can fundamentally change our understanding of space and time, shedding light on billions of cosmic mysteries.

Formation of black holes

As long as thermonuclear reactions take place in the interior of a star, they support high temperature and pressure, preventing the star from collapsing under its own gravity. However, over time, the nuclear fuel is depleted, and the star begins to shrink. Calculations show that if the mass of a star does not exceed three solar masses, then it will win the “battle with gravity”: its gravitational collapse will be stopped by the pressure of “degenerate” matter, and the star will forever turn into a white dwarf or neutron star. But if the mass of a star is more than three solar, then nothing can stop its catastrophic collapse and it will quickly go under the event horizon, becoming a black hole.

Is a black hole a donut hole?

Anything that doesn't emit light is hard to see. One way to search for a black hole is to look for regions in open space, which have a large mass and are located in a dark space. When searching for these types of objects, astronomers have found them in two main areas: at the centers of galaxies and in binary star systems in our Galaxy. In total, as scientists suggest, there are tens of millions of such objects.

At present, the only reliable way to distinguish a black hole from another type of object is to measure the mass and size of the object and compare its radius with