Scientific thinking sometimes constructs objects with such paradoxical properties that even the most astute scientists at first refuse to recognize them. The most obvious example in the history of modern physics is the long-term lack of interest in black holes, extreme states of the gravitational field predicted almost 90 years ago. For a long time they were considered a purely theoretical abstraction, and only in the 1960s and 70s did they believe in their reality. However, the basic equation of the theory of black holes was derived over two hundred years ago.

John Michell's insight

The name of John Michell, physicist, astronomer and geologist, professor at the University of Cambridge and pastor of the Church of England, was completely undeservedly lost among the stars of English science in the 18th century. Michell laid the foundations of seismology, the science of earthquakes, performed an excellent study of magnetism, and long before Coulomb invented the torsion balance that he used for gravimetric measurements. In 1783, he tried to combine Newton's two great creations, mechanics and optics. Newton considered light to be a stream of tiny particles. Michell suggested that light corpuscles, like ordinary matter, obey the laws of mechanics. The consequence of this hypothesis turned out to be very non-trivial - celestial bodies can turn into traps for light.

How did Michell think? A cannonball fired from the surface of a planet will completely overcome its gravity only if its initial velocity exceeds what is now called second space velocity and escape velocity. If the planet's gravity is so strong that the escape velocity exceeds the speed of light, light corpuscles fired at the zenith cannot escape to infinity. The same will happen with reflected light. Therefore, for a very distant observer, the planet will be invisible. Michell calculated the critical value of the radius of such a planet, Rcr, depending on its mass, M, reduced to the mass of our Sun, Ms: Rcr = 3 km x M/Ms.

John Michell believed in his formulas and assumed that the depths of space hide many stars that cannot be seen from Earth with any telescope. Later, the great French mathematician, astronomer and physicist Pierre Simon Laplace came to the same conclusion and included it in both the first (1796) and the second (1799) editions of his Exposition of the System of the World. But the third edition was published in 1808, when most physicists already considered light to be vibrations of the ether. The existence of "invisible" stars contradicted the wave theory of light, and Laplace thought it best to simply not mention them. In subsequent times, this idea was considered a curiosity, worthy of exposition only in works on the history of physics.

Schwarzschild model

In November 1915, Albert Einstein published a theory of gravity, which he called the general theory of relativity (GR). This work immediately found an appreciative reader in the person of his colleague from the Berlin Academy of Sciences Karl Schwarzschild. It was Schwarzschild who was the first in the world to apply general relativity to solve a specific astrophysical problem, to calculate the space-time metric outside and inside a non-rotating spherical body (for concreteness, we will call it a star).

It follows from Schwarzschild's calculations that the gravity of a star does not greatly distort the Newtonian structure of space and time only if its radius is much larger than the very value that John Michell calculated! This parameter was first called the Schwarzschild radius, and is now called the gravitational radius. According to general relativity, gravity does not affect the speed of light, but reduces the frequency of light vibrations in the same proportion in which it slows down time. If the radius of a star is 4 times greater than the gravitational radius, then the flow of time on its surface slows down by 15%, and space acquires a noticeable curvature. With a double excess, it bends more, and time slows down its run by 41%. When the gravitational radius is reached, time on the surface of the star stops completely (all frequencies are zeroed, the radiation is frozen, and the star goes out), but the curvature of space there is still finite. Far from the sun, the geometry still remains Euclidean, and time does not change its speed.

Despite the fact that the values ​​of the gravitational radius for Michell and Schwarzschild are the same, the models themselves have nothing in common. For Michell, space and time do not change, but light slows down. A star whose dimensions are smaller than its gravitational radius continues to shine, but it is visible only to a not too distant observer. For Schwarzschild, the speed of light is absolute, but the structure of space and time depends on gravity. A star that has fallen under the gravitational radius disappears for any observer, no matter where he is (more precisely, it can be detected by gravitational effects, but by no means by radiation).

From disbelief to assertion

Schwarzschild and his contemporaries believed that such strange cosmic objects do not exist in nature. Einstein himself not only adhered to this point of view, but also mistakenly believed that he managed to substantiate his opinion mathematically.

In the 1930s, a young Indian astrophysicist, Chandrasekhar, proved that a star that has spent its nuclear fuel sheds its shell and turns into a slowly cooling white dwarf only if its mass is less than 1.4 solar masses. Soon, the American Fritz Zwicky guessed that extremely dense bodies of neutron matter arise in supernova explosions; Later, Lev Landau came to the same conclusion. After the work of Chandrasekhar, it was obvious that only stars with a mass greater than 1.4 solar masses could undergo such an evolution. Therefore, a natural question arose - is there an upper mass limit for supernovae that neutron stars leave behind?

In the late 1930s, the future father of the American atomic bomb, Robert Oppenheimer, established that such a limit does indeed exist and does not exceed several solar masses. It was not possible then to give a more precise assessment; it is now known that the masses of neutron stars must be in the range 1.5-3 M s . But even from the approximate calculations of Oppenheimer and his graduate student George Volkov, it followed that the most massive descendants of supernovae do not become neutron stars, but go into some other state. In 1939, Oppenheimer and Hartland Snyder proved in an idealized model that a massive collapsing star contracts to its gravitational radius. From their formulas, in fact, it follows that the star does not stop there, but the co-authors refrained from such a radical conclusion.

The final answer was found in the second half of the 20th century by the efforts of a galaxy of brilliant theoretical physicists, including Soviet ones. It turned out that such a collapse always compresses the star "to the stop", completely destroying its substance. As a result, a singularity arises, a "superconcentrate" of the gravitational field, closed in an infinitely small volume. For a fixed hole, this is a point, for a rotating hole, it is a ring. The curvature of space-time and, consequently, the force of gravity near the singularity tend to infinity. In late 1967, American physicist John Archibald Wheeler was the first to call such a final stellar collapse a black hole. The new term fell in love with physicists and delighted journalists who spread it around the world (although the French did not like it at first, because the expression trou noir suggested dubious associations).

There, beyond the horizon

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

The physical meaning of the horizon is very clear. A light signal sent from its outer neighborhood can travel an infinite distance. But the signals sent from the inner region will not only not cross the horizon, but will inevitably “fall” into the singularity. The horizon is the spatial boundary between events that can become known to terrestrial (and any other) astronomers, and events that information about which will not come out under any circumstances.

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

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

black hole radiation

All previous models were built exclusively on the basis of general relativity. However, our world is governed by the laws of quantum mechanics, which do not ignore black holes. These laws do not allow us to consider the central singularity as a mathematical point. In a quantum context, its diameter is given by the Planck-Wheeler length, approximately equal to 10 -33 centimeters. In this region, ordinary space ceases to exist. It is generally accepted that the center of the hole is stuffed with various topological structures that appear and die in accordance with quantum probabilistic laws. The properties of such a bubbling quasi-space, which Wheeler called quantum foam, are still poorly understood.

The presence of a quantum singularity is directly related to the fate of material bodies falling deep into a black hole. When approaching the center of the hole, any object made from currently known materials will be crushed and torn apart by tidal forces. However, even if future engineers and technologists create some super-strong alloys and composites with properties unheard of today, they are all doomed to disappear anyway: after all, in the singularity zone there is neither familiar time nor familiar space.

Now let's look at the horizon of the hole through a quantum mechanical lens. Empty space - the physical vacuum - is in fact by no means empty. Due to quantum fluctuations of various fields in vacuum, many virtual particles are continuously born and die. Since gravity near the horizon is very strong, its fluctuations create extremely strong gravitational bursts. When accelerated in such fields, newborn "virtuals" acquire additional energy and sometimes become normal long-lived particles.

Virtual particles are always born in pairs that move in opposite directions (this is required by the law of conservation of momentum). If a gravitational fluctuation extracts a pair of particles from the vacuum, it may happen that one of them materializes outside the horizon, and the second (the antiparticle of the first) inside. The "internal" particle will fall into the hole, but the "external" particle can escape under favorable conditions. As a result, the hole turns into a source of radiation and therefore loses energy and, consequently, mass. Therefore, black holes are fundamentally unstable.

This phenomenon is called the Hawking effect, after the remarkable English theoretical physicist who discovered it in the mid-1970s. Stephen Hawking, in particular, proved that the horizon of a black hole emits photons in exactly the same way as an absolutely black body heated to a temperature T = 0.5 x 10 -7 x M s /M. It follows that as the hole becomes thinner, its temperature increases, and the "evaporation", of course, increases. This process is extremely slow, and the lifetime of a hole of mass M is about 10 65 x (M/M s) 3 years. When its size becomes equal to the Planck-Wheeler length, the hole loses stability and explodes, releasing the same energy as the simultaneous explosion of a million ten-megaton hydrogen bombs. Curiously, the mass of the hole at the time of its disappearance is still quite large, 22 micrograms. According to some models, the hole does not disappear without a trace, but leaves behind a stable relic of the same mass, the so-called maximon.

Maximon was born 40 years ago - as a term and as a physical idea. In 1965, Academician M. A. Markov suggested that there is an upper limit on the mass of elementary particles. He suggested that this limit value be considered the dimension of mass, which can be combined from three fundamental physical constants - Planck's constant h, the speed of light C and the gravitational constant G (for lovers of details: to do this, you need to multiply h and C, divide the result by G and extract the square root). These are the same 22 micrograms that are mentioned in the article, this value is called the Planck mass. From the same constants it is possible to construct a value with the dimension of length (the Planck-Wheeler length will come out, 10 -33 cm) and with the dimension of time (10 -43 sec).
Markov went further in his reasoning. According to his hypothesis, the evaporation of a black hole leads to the formation of a "dry residue" - a maximon. Markov called such structures elementary black holes. To what extent this theory corresponds to reality is still an open question. In any case, analogues of Markov maximons have been revived in some models of black holes based on superstring theory.

Depths of space

Black holes are not forbidden by the laws of physics, but do they exist in nature? Absolutely strict evidence of the presence in space of at least one such object has not yet been found. However, it is highly probable that in some binary systems the X-ray sources are black holes of stellar origin. This radiation should arise as a result of the suction of the atmosphere of an ordinary star by the gravitational field of a neighboring hole. The gas during its movement to the event horizon is strongly heated and emits X-ray quanta. At least two dozen X-ray sources are now considered suitable candidates for the role of black holes. Moreover, stellar statistics suggest that there are about ten million holes of stellar origin in our Galaxy alone.

Black holes can also form in the process of gravitational condensation of matter in galactic nuclei. This is how gigantic holes with a mass of millions and billions of solar masses arise, which, in all likelihood, are found in many galaxies. Apparently, in the center of the Milky Way, covered with dust clouds, there is a hole with a mass of 3-4 million solar masses.

Stephen Hawking came to the conclusion that black holes of arbitrary mass could be born immediately after the Big Bang, which gave rise to our Universe. Primary holes weighing up to a billion tons have already evaporated, but heavier ones can still hide in the depths of space and, in due course, set up cosmic fireworks in the form of powerful flashes of gamma radiation. However, such explosions have never been observed so far.

black hole factory

Is it possible to accelerate the particles in the accelerator to such a high energy that their collision would give rise to a black hole? At first glance, this idea is simply crazy - the explosion of the hole will destroy all life on Earth. Moreover, it is technically unfeasible. If the minimum mass of a hole is indeed 22 micrograms, then in energy units it is 10 28 electron volts. This threshold is 15 orders of magnitude higher than the world's most powerful accelerator, the Large Hadron Collider (LHC), which will be launched at CERN in 2007.

However, it is possible that the standard estimate of the minimum mass of a hole is significantly overestimated. In any case, this is what the physicists who develop the theory of superstrings say, which includes the quantum theory of gravity (though far from complete). According to this theory, space has not less than three dimensions, but at least nine. We do not notice extra dimensions, because they are looped in such a small scale that our instruments do not perceive them. However, gravity is omnipresent, it penetrates into hidden dimensions. In three dimensions, the force of gravity is inversely proportional to the square of the distance, and in nine dimensions it is the eighth power. Therefore, in a multidimensional world, the intensity of the gravitational field increases much faster with decreasing distance than in a three-dimensional one. In this case, the Planck length increases many times, and the minimum mass of the hole drops sharply.

String theory predicts that a black hole with a mass of only 10 -20 g can be born in nine-dimensional space. The calculated relativistic mass of protons accelerated in the zern superaccelerator is approximately the same. According to the most optimistic scenario, he will be able to produce one hole every second, which will live for about 10 -26 seconds. In the process of its evaporation, all kinds of elementary particles will be born, which will be easy to register. The disappearance of the hole will lead to the release of energy, which is not enough even to heat one microgram of water per thousandth of a degree. Therefore, there is hope that the LHC will turn into a factory of harmless black holes. If these models are correct, then new generation orbital cosmic ray detectors will also be able to detect such holes.

All of the above applies to stationary black holes. Meanwhile, there are rotating holes that have a bunch of interesting properties. The results of the theoretical analysis of black hole radiation also led to a serious rethinking of the concept of entropy, which also deserves a separate discussion. More on that in the next issue.

The hypothesis of the existence of black holes was first put forward by the English astronomer J. Michell in 1783 on the basis of the corpuscular theory of light and the Newtonian theory of gravity. At that time, Huygens' wave theory and his famous wave principle were simply forgotten. The wave theory was not helped by the support of some venerable scientists, in particular, the famous St. Petersburg academicians M.V. Lomonosov and L. Euler. The logic of reasoning that led Michell to the concept of a black hole is very simple: if light consists of particles-corpuscles of the luminiferous ether, then these particles, like other bodies, must experience attraction from the gravitational field. Consequently, the more massive the star (or planet), the greater the attraction from its side to corpuscles and the more difficult it is for light to leave the surface of such a body.

Further logic suggests that such massive stars can exist in nature, the attraction of which the corpuscles can no longer overcome, and they will always appear black to an external observer, although they themselves can glow with a dazzling brilliance, like the Sun. Physically, this means that the second cosmic velocity on the surface of such a star must be no less than the speed of light. Michell's calculations show that light will never leave a star if its radius at average solar density is 500 solar. Such a star can already be called a black hole.

After 13 years, the French mathematician and astronomer P.S. Laplace expressed, most likely, independently of Michell, a similar hypothesis about the existence of such exotic objects. Using a cumbersome calculation method, Laplace found the radius of a sphere for a given density, on the surface of which the parabolic velocity is equal to the speed of light. According to Laplace, corpuscles of light, being gravitating particles, should be delayed by massive stars emitting light, which have a density equal to that of the Earth, and a radius 250 times greater than the solar one.

This theory of Laplace was included only in the first two lifetime editions of his famous book "Exposition of the System of the World", published in 1796 and 1799. Yes, perhaps even the Austrian astronomer F.K. von Zach became interested in Laplace's theory, publishing it in 1798 under the title "Proof of the theorem that the force of attraction of a heavy body can be so great that light cannot flow out of it."

At this point, the history of the study of black holes stopped for more than 100 years. It seems that Laplace himself quietly abandoned such an extravagant hypothesis, since he excluded it from all other lifetime editions of his book, which appeared in 1808, 1813 and 1824. Perhaps Laplace did not want to replicate the almost fantastic hypothesis of colossal stars that do not emit light anymore. Perhaps he was stopped by new astronomical data on the invariance of the magnitude of the aberration of light in different stars, which contradicted some of the conclusions of his theory, on the basis of which he based his calculations. But the most likely reason why everyone forgot about the mysterious hypothetical objects of Michell-Laplace is the triumph of the wave theory of light, the triumphal procession of which began from the first years of the 19th century.

The beginning of this triumph was laid by the Booker lecture of the English physicist T. Jung "The Theory of Light and Color", published in 1801, where Jung boldly, contrary to Newton and other famous supporters of the corpuscular theory (including Laplace), outlined the essence of the wave theory of light, saying that the emitted light consists of wave-like movements of the luminiferous ether. Inspired by the discovery of the polarization of light, Laplace began to "save" corpuscles by constructing a theory of double refraction of light in crystals based on the double action of crystal molecules on light corpuscles. But the subsequent works of physicists O.Zh. Fresnel, F.D. Aragon, J. Fraunhofer and others left no stone unturned in the corpuscular theory, which was seriously remembered only a century later, after the discovery of quanta. All reasoning about black holes in the framework of the wave theory of light at that time looked ridiculous.

Black holes were not immediately remembered after the "rehabilitation" of the corpuscular theory of light, when they started talking about it at a new qualitative level thanks to the hypothesis of quanta (1900) and photons (1905). Black holes were rediscovered for the second time only after the creation of general relativity in 1916, when the German theoretical physicist and astronomer K. Schwarzschild, a few months after the publication of Einstein's equations, used them to investigate the structure of curved space-time in the vicinity of the Sun. As a result, he rediscovered the phenomenon of black holes, but at a deeper level.

The final theoretical discovery of black holes took place in 1939, when Oppenheimer and Snyder performed the first explicit solution of Einstein's equations in describing the formation of a black hole from a collapsing dust cloud. The term "black hole" itself was first introduced into science by the American physicist J. Wheeler in 1968, during the years of a rapid revival of interest in general relativity, cosmology and astrophysics, caused by the achievements of extra-atmospheric (in particular, x-ray) astronomy, the discovery of cosmic microwave background radiation, pulsars and quasars.

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 would need to overcome the gravitational pull 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: "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:

• Black hole without rotation and without charge - Schwarzschild's solution. One of the first descriptions of a black hole (1916) using Einstein's equations, but without taking into account two of the three parameters of the body. The solution of the German physicist Karl Schwarzschild allows you to calculate the external gravitational field of a spherical massive body. A feature of the German scientist's concept of black holes is the presence of an event horizon and the one behind it. Schwarzschild also first calculated the gravitational radius, which received his name, which determines the radius of the sphere on which the event horizon would be located for a body with a given mass.
• A black hole without rotation with a charge - the Reisner-Nordström solution. A solution put forward in 1916-1918, taking into account the possible electric charge of a black hole. This charge cannot be arbitrarily large and is limited due to the resulting electrical repulsion. The latter must be compensated by gravitational attraction.
• A black hole with rotation and no charge - Kerr's solution (1963). A rotating Kerr black hole differs from a static one by the presence of the so-called ergosphere (read on about this and other components of a black hole).
• BH with rotation and charge - Kerr-Newman solution. This solution was calculated in 1965 and is currently the most complete, since it takes into account all three BH parameters. However, it is still assumed that black holes in nature have an insignificant charge.

The formation of a black hole

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

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

Two other scenarios remain hypothetical:

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

Structure and physics of black holes

The structure of a black hole according to Schwarzschild includes only two elements that were mentioned earlier: the singularity and the event horizon of a black hole. Briefly speaking about the singularity, it can be noted that it is impossible to draw a straight line through it, and also that most of the existing physical theories do not work inside it. Thus, the physics of the singularity remains a mystery to scientists today. black hole - this is a kind of border, crossing which, a physical object loses the ability to return back beyond it and unequivocally "fall" into the singularity of a black hole.

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

• How much does a black hole weigh? - The greatest theoretical material on the appearance of a black hole is available for the scenario of its appearance as a result of the collapse of a star. In this case, the maximum mass of a neutron star and the minimum mass of a black hole are determined by the Oppenheimer-Volkov limit, according to which the lower limit of the BH mass is 2.5 - 3 solar masses. The heaviest black hole ever discovered (in the galaxy NGC 4889) has a mass of 21 billion solar masses. However, one should not forget about black holes, hypothetically resulting from nuclear reactions at high energies, such as those at colliders. The mass of such quantum black holes, in other words "Planck black holes" is of the order of , namely 2 10 −5 g.
• Black hole size. The minimum BH radius can be calculated from the minimum mass (2.5 - 3 solar masses). If the gravitational radius of the Sun, that is, the area where the event horizon would be, is about 2.95 km, then the minimum radius of a BH of 3 solar masses will be about nine kilometers. Such relatively small sizes do not fit in the head when it comes to massive objects that attract everything around. However, for quantum black holes, the radius is -10 −35 m.
• The average density of a black hole depends on two parameters: mass and radius. The density of a black hole with a mass of about three solar masses is about 6 10 26 kg/m³, while the density of water is 1000 kg/m³. However, such small black holes have not been found by scientists. Most of the detected BHs have masses greater than 105 solar masses. There is an interesting pattern according to which the more massive the black hole, the lower its density. In this case, a change in mass by 11 orders of magnitude entails a change in density by 22 orders of magnitude. Thus, a black hole with a mass of 1 ·10 9 solar masses has a density of 18.5 kg/m³, which is one less than the density of gold. And black holes with a mass of more than 10 10 solar masses can have an average density less than the density of air. Based on these calculations, it is logical to assume that the formation of a black hole occurs not due to the compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume. In the case of quantum black holes, their density can be about 10 94 kg/m³.
• The temperature of a black hole is also inversely proportional to its mass. This temperature is directly related to . The spectrum of this radiation coincides with the spectrum of a completely black body, that is, a body that absorbs all incident radiation. The radiation spectrum of a black body depends only on its temperature, then the temperature of a black hole can be determined from the Hawking radiation spectrum. As mentioned above, this radiation is the more powerful, the smaller the black hole. At the same time, Hawking radiation remains hypothetical, since it has not yet been observed by astronomers. It follows from this that if Hawking radiation exists, then the temperature of the observed BHs is so low that it does not allow one to detect the indicated radiation. According to calculations, even the temperature of a hole with a mass on the order of the mass of the Sun is negligibly small (1 ·10 -7 K or -272°C). The temperature of quantum black holes can reach about 10 12 K, and with their rapid evaporation (about 1.5 min.), such 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 what a person will feel in this situation. It is worth noting that the effect of stretching the body is inversely proportional to the mass of the black hole. That is, if a BH with the mass of three Suns instantly stretches/breaks the body, then the supermassive black hole will have lower tidal forces and, there are suggestions that some physical materials could “tolerate” such a deformation without losing their structure.

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

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

Despite what has been written above, it is assumed that in very large supermassive black holes, tidal forces do not change so much with distance and act almost uniformly on the falling body. In such a case, the falling spacecraft would retain its structure. A reasonable question arises - where does a 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-Thorne wormhole, so in the case of black and white holes, the possibility of travel requires the existence of so-called exotic matter, which has negative energy and also remains hypothetical.

Black holes in the universe

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

• stellar mass black hole. Such objects are formed as a result of the collapse of a star. As mentioned earlier, the minimum mass of a body capable of forming such a black hole is 2.5 - 3 solar masses.
• 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, with the help of 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 (light particles) are not attracted by massive objects, since according to the theory they themselves have no mass. However, the black hole still "attracts" the photons of light through the distortion of space-time. If we imagine a black hole in space as a kind of depression on the smooth surface of space-time, then there is a certain distance from the center of the black hole, approaching which light will no longer be able to move away from it. That is, roughly speaking, the light begins to "fall" into the "pit", which does not even have a "bottom".

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

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

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

Merging and colliding black holes

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

According to the definition of gravitational waves, these are changes in the gravitational field that propagate in a wave-like manner from massive moving objects. When two such objects approach each other, they begin to rotate around a common center of gravity. As they approach each other, their rotation around their own axis increases. Such variable oscillations of the gravitational field at some point can form one powerful gravitational wave that can propagate in space for millions of light years. So, at a distance of 1.3 billion light years, a collision of two black holes occurred, which formed a powerful gravitational wave that reached the Earth on September 14, 2015 and was recorded by the LIGO and VIRGO detectors.

How do black holes die?

Obviously, for a black hole to cease to exist, it would need to lose all of its mass. However, according to her definition, nothing can leave the black hole if it has crossed its event horizon. It is known that for the first time the Soviet theoretical physicist Vladimir Gribov mentioned the possibility of emission of particles by a black hole in his discussion with another Soviet scientist Yakov Zel'dovich. He argued that from the point of view of quantum mechanics, a black hole is capable of emitting particles through a tunnel effect. Later, with the help of quantum mechanics, he built his own, somewhat different theory, the English theoretical physicist Stephen Hawking. You can read more about this phenomenon. In short, in vacuum there are so-called virtual particles that are constantly born in pairs and annihilate each other, while not interacting with the outside world. But if such pairs arise at the black hole's event horizon, then strong gravity is hypothetically able to separate them, with one particle falling into the black hole, and the other going away from the black hole. And since a particle that has flown away from a hole can be observed, and therefore has positive energy, a particle that has fallen into a hole must have negative energy. Thus, the black hole will lose its energy and there will be an effect called black hole evaporation.

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

Despite 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".

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

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

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

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

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

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

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

What are black holes really?

A laconic explanation of the phenomenon sounds like this.

A black hole is a space-time region whose gravitational attraction is so strong that no object, including light quanta, can leave it.

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

• 1. Ejection of a black hole jet at high speed


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


• 3. Black hole


• 4. Detailed scheme of the black hole region


• 5. Size of found new observations

The most common theory says that there are similar phenomena in every galaxy, including in the center of our Milky Way. The huge gravity of the hole is capable of holding several galaxies around it, preventing them from moving away from each other. The "coverage area" can be different, it all depends on the mass of the star that has turned into a black hole, and can be thousands of light years.

Schwarzschild radius

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

• 1. Moving matter at half the speed of light


• 2. Photon ring


• 3. Inner photon ring


• 4. The event horizon in a black hole

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

How does it fall into a black hole

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

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

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

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


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


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


• 4. After the cloud is broken, most of it will most likely 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.

Ohio University astronomers recently announced that the unusual double core in the Andromeda galaxy is due to a cluster of stars orbiting in elliptical orbits around some massive object, most likely a black hole. Such conclusions were made on the basis of data obtained using the Hubble Space Telescope. The double core of Andromeda was first discovered in the 70s, but it wasn't until the mid 90s that the theory of black holes was put forward.

The idea that black holes exist in the cores of galaxies is not new.

There is even every reason to believe that the Milky Way - the galaxy to which the Earth belongs - has a large black hole in its core, the mass of which is 3 million times the mass of the Sun. However, it is easier to explore the core of the Andromeda galaxy, which is located at a distance of 2 million light years from us, than the core of our galaxy, to which light travels only 30 thousand years - you cannot see the forest for the trees.

Scientists simulate black hole collisions

Application of numerical simulation on supercomputers to elucidate the nature and behavior of black holes, the study of gravitational waves.

For the first time, scientists from the Institute of Gravitational Physics (Max-Planck-Institut fur Gravitationsphysik), also known as the "Albert Einstein Institute" and located in Holm, a suburb of Potsdam (Germany), simulated the merger of two black holes. The planned detection of gravitational waves emitted by the two merging black holes requires full 3D simulations on supercomputers.

Black holes are so dense that they do not reflect or emit light at all, which is why they are so difficult to detect. However, in a few years, scientists hope for a significant shift in this area.

Gravitational waves, which literally fill the outer space, at the beginning of the next century can be detected with the help of new means.

Scientists led by Professor Ed Seidel (Dr. Ed Seidel) are preparing numerical simulations for such studies, which will be a reliable way for observers to detect waves produced by black holes. "Black hole collisions are one of the main sources of gravitational waves," said Professor Seidel, who in recent years has been doing successful research in modeling gravitational waves that appear when black holes break up in direct collisions.

However, the interaction of two spiraling black holes and their merger is more common than a direct collision, and is of greater importance in astronomy. Such tangential collisions were first calculated by Bernd Brugmann at the Albert Einstein Institute.

However, at that time, due to a lack of computing power, he could not calculate such fundamentally important details as the exact trace of emitted gravitational waves, which contains important information about the behavior of black holes during a collision. Brugman published the latest results in the International Journal of Modern Physics.

In his first calculations, Brugman used the institute's Origin 2000 server. It includes 32 separate processors running in parallel with a total peak performance of 3 billion operations per second. And in June of this year, an international team of Brugmann, Seidel and others were already working on the much more powerful 256-processor Origin 2000 supercomputer at the National Center for Supercomputing Applications (NCSA). The group also included scientists from

Louis University (USA) and from the research center Konrad-Zuse-Zentrum in Berlin. This supercomputer provided the first detailed simulation of the tangential collisions of unequal-mass black holes, as well as their rotations, which Brugmann had previously explored. Werner Benger from Konrad-Zuse-Zentrum even managed to reproduce a stunning picture of the collision process. It was demonstrated how "black monsters" with masses from one to several hundred million solar masses merged, creating flashes of gravitational waves, which could soon be recorded by special means.

One of the most important results of this research work was the discovery of the huge energy emitted by the collision of black holes in the form of gravitational waves. If two objects with masses equivalent to 10 and 15 solar masses approach each other closer than 30 miles and collide, then the amount of gravitational energy corresponds to 1% of their mass. "This is a thousand times more than all the energy released by our Sun over the past five billion years." Brugman noted. Since most major collisions in the universe occur very far from the earth, the signals should become very weak by the time they hit the ground.

The construction of several high-precision detectors has begun around the world.

One of them, built by the Max Planck Institute in the framework of the German-British project "Geo 600" is a laser interferometer with a length of 0.7 miles. Scientists hope to measure the parameters of the short gravitational perturbations that occur when black holes collide, but they expect only one such collision per year, and at a distance of about 600 million light-years. Computer models are needed to provide observers with reliable information about the detection of waves produced by black holes. Thanks to improvements in supercomputer simulation capabilities, scientists are on the cusp of a new type of experimental physics.

Astronomers say they know the location of many thousands of black holes, but we are not in a position to do any experiments on them on earth. "Only in one case will we be able to study the details and construct their numerical model in our computers and observe it," explained Professor Bernard Schutz, director of the Albert Einstein Institute. "I believe that the study of black holes will be a key research topic for astronomers in the first decade of the next century."

The satellite star allows you to see the dust from the supernova.

Black holes cannot be seen directly, but astronomers can see evidence of their existence when gases erupt into a companion star.

If the dynamite is detonated, then tiny fragments of the explosive will pierce deeply into nearby objects, thus leaving indelible evidence of an explosion.

Astronomers have found a similar imprint on a star orbiting a black hole, not without reason believing that this black hole - a former star that collapsed so badly that even light cannot overcome its gravitational force - was the result of a supernova explosion.

The light in the darkness.

By this time, astronomers had observed supernova explosions and found spotted objects in their place, which, in their opinion, are black holes. The new discovery is the first real proof of a connection between one event and another. (Black holes cannot be directly seen, but their presence can sometimes be inferred from the effect of their gravitational field on nearby objects.

The star-and-black hole system, designated GRO J1655-40, lies approximately 10,000 light-years away within our Milky Way galaxy. Discovered in 1994, it caught the attention of astronomers with intense bursts of X-rays and a barrage of radio waves as the black hole expelled gases toward its companion star 7.4 million miles away.

Researchers from Spain and America began to look closely at the companion star, believing that it could retain some kind of trace, indicating the process of forming a black hole.

Star-sized black holes are thought to be the bodies of large stars that have simply shrunk to that size after having used up all their hydrogen fuel. But for reasons not yet understood, the fading star transforms into a supernova before exploding.

Observations by the GRO J1655-40 system in August and September 1994 made it possible to fix that the streams of ejected gas had a speed of up to 92% of the speed of light, which partially proved the presence of a black hole there.

Star dust.

If scientists are not mistaken, then some of the exploded stars, which are probably 25-40 times larger than our Sun, turned into surviving satellites.

This is exactly the data that astronomers have found.

The companion star's atmosphere contained a higher-than-usual concentration of oxygen, magnesium, silicon and sulfur - heavy elements that can only be created in abundance at the multibillion-degree temperature that is reached during a supernova explosion. This was the first evidence that really confirmed the validity of the theory that some black holes first appeared as supernovae, since what they saw could not be born by the star that astronomers observed.