Predicts that there is a singularity in a black hole, a place where tidal forces become infinitely large, and once you get past the event horizon, you can no longer go anywhere other than the singularity. Accordingly, it is better not to use general relativity in these places - it simply does not work. To tell what happens inside a black hole, we need a theory of quantum gravity. It is generally accepted that this theory will replace the singularity with something else.

How do black holes form?

We currently know of four different ways black holes form. Best understood is associated with stellar collapse. A large enough star forms a black hole after its nuclear fusion stops, because everything that could already be synthesized has been synthesized. When the pressure created by fusion ceases, matter begins to fall towards its own gravitational center, becoming more and more dense. In the end, it becomes so dense that nothing can overcome the gravitational effect on the surface of the star: this is how a black hole is born. These black holes are called "solar mass black holes" and are the most common.

The next common type of black hole is "supermassive black holes", which can be found at the centers of many galaxies and have masses about a billion times that of solar black holes. It is not yet known for certain exactly how they are formed. It is believed that they once began as solar-mass black holes that swallowed up many other stars in densely populated galactic centers and grew. However, they seem to absorb matter faster than this simple idea suggests, and how exactly they do it is still a matter of research.

A more controversial idea has become primordial black holes, which could have been formed by virtually any mass in large density fluctuations in the early universe. While it is possible, it is difficult to find a model that produces them without over-creating them.

Finally, there is the very speculative idea that tiny black holes with masses close to that of the Higgs boson could form at the Large Hadron Collider. This only works if our universe has extra dimensions. So far, there has been no confirmation in favor of this theory.

How do we know black holes exist?

We have a lot of observational evidence for compact objects with large masses that do not emit light. These objects give themselves away by gravitational attraction, for example, due to the movement of other stars or gas clouds around them. They also create gravitational lensing. We know that these objects do not have a solid surface. This follows from observations, because matter falling on an object with a surface should cause the release of more particles than matter falling through the horizon.

Why did Hawking say last year that black holes don't exist?

He meant that black holes do not have an eternal event horizon, but only a temporary apparent horizon (see paragraph one). In a strict sense, only the event horizon is considered a black hole.

How do black holes emit radiation?

Black holes emit radiation due to quantum effects. It is important to note that these are quantum effects of matter, not quantum effects of gravity. The dynamic spacetime of a collapsing black hole changes the very definition of a particle. Like the passage of time, which is distorted next to a black hole, the concept of particles is too dependent on the observer. In particular, when an observer falling into a black hole thinks that he is falling into a vacuum, an observer far from the black hole thinks that this is not a vacuum, but a space full of particles. It is the stretching of space-time that causes this effect.

First discovered by Stephen Hawking, the radiation emitted by a black hole is called Hawking radiation. This radiation has a temperature inversely proportional to the mass of the black hole: the smaller the black hole, the higher the temperature. The stellar and supermassive black holes that we know have temperatures well below the temperature of the microwave background and therefore are not observed.

What is an information paradox?

The information loss paradox is caused by Hawking radiation. This radiation is purely thermal, that is, it has only temperature by chance and of certain properties. The radiation itself does not contain any information about how the black hole formed. But when a black hole emits radiation, it loses mass and contracts. All this is completely independent of the substance that became part of the black hole or from which it was formed. It turns out that knowing only the final state of evaporation, one cannot say from what the black hole was formed. This process is "irreversible" - and the catch is that there is no such process in quantum mechanics.

It turns out that the evaporation of a black hole is incompatible with the quantum theory as we know it, and something needs to be done about it. Eliminate the inconsistency somehow. Most physicists believe the solution is that Hawking radiation must somehow contain information.

What does Hawking propose to solve the black hole information paradox?

The idea is that black holes must have a way to store information that has not yet been accepted. The information is stored on the horizon of the black hole and can cause tiny displacements of particles in Hawking radiation. In these tiny displacements, there may be information about the trapped matter. The exact details of this process are currently not defined. Scientists are awaiting a more detailed white paper from Stephen Hawking, Malcolm Perry and Andrew Strominger. They say it will appear at the end of September.

At the moment, we are sure that black holes exist, we know where they are, how they form and what they will become in the end. But the details of where the information goes to them still represent one of the greatest mysteries of the universe.

January 24th, 2013

Of all the hypothetical objects in the universe predicted by scientific theories, black holes make the most eerie impression. And, although the assumptions about their existence began to be expressed almost a century and a half before Einstein's publication of general relativity, convincing evidence of the reality of their existence was obtained quite recently.

Let's start by looking at how general relativity addresses the question of the nature of gravity. Newton's law of universal gravitation states that a force of mutual attraction acts between any two massive bodies in the Universe. Because of this gravitational attraction, the Earth revolves around the Sun. General relativity forces us to look at the Sun-Earth system differently. According to this theory, in the presence of such a massive celestial body as the Sun, space-time seems to be perforated under its weight, and the uniformity of its tissue is disturbed. Imagine an elastic trampoline with a heavy ball (for example, from a bowling alley) resting on it. The stretched fabric bends under its weight, creating a vacuum around it. In the same way, the Sun pushes space-time around it.

According to this picture, the Earth simply rolls around the formed funnel (except that a small ball rolling around a heavy one on a trampoline will inevitably lose speed and spiral closer to a large one). And what we habitually perceive as the force of gravity in our daily life is also nothing more than a change in the geometry of space-time, and not a force in Newtonian understanding. Today, no more successful explanation of the nature of gravity than the general theory of relativity gives us has been invented.

Now imagine what will happen if we - within the framework of the proposed picture - increase and increase the mass of a heavy ball without increasing its physical size? Being absolutely elastic, the funnel will deepen until its upper edges converge somewhere high above the completely heavy ball, and then it simply ceases to exist when viewed from the surface. In the real Universe, having accumulated sufficient mass and density of matter, the object slams a space-time trap around itself, the fabric of space-time closes, and it loses its connection with the rest of the Universe, becoming invisible to it. This is how a black hole appears.

Schwarzschild and his contemporaries believed that such strange space objects did not exist in nature. Einstein himself not only held this point of view, but also mistakenly believed that he had succeeded in substantiating his opinion mathematically.

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

In the late 1930s, the future father of the American atomic bomb, Robert Oppenheimer, established that such a limit does exist and does not exceed a few solar masses. At that time it was not possible to give a more accurate assessment; it is now known that the masses of neutron stars must be in the range of 1.5-3 Ms. 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, using an idealized model, proved that a massive collapsing star is contracting to its gravitational radius. From their formulas, it actually follows that the star does not stop there, but the co-authors refrained from such a radical conclusion.

09.07.1911 - 13.04.2008

The final answer was found in the second half of the 20th century through the efforts of a whole galaxy of brilliant theoretical physicists, including Soviet ones. It turned out that such a collapse always compresses the star "all the way", completely destroying its substance. As a result, a singularity arises, a "superconcentrate" of the gravitational field, closed in an infinitely small volume. For a stationary hole, this is a point, for a rotating one, a ring. The curvature of space-time and, consequently, the gravitational force near the singularity tends to infinity. At the end of 1967, the 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, since the expression trou noir suggested dubious associations).

The most important property of a black hole is that whatever gets into it, it will not come back. This even applies to light, which is why black holes got their name: a body that absorbs all the light falling on it and does not emit its own seems to be absolutely black. According to general relativity, if an object approaches the center of a black hole at a critical distance - this distance is called the Schwarzschild radius - it can never go back. (German astronomer Karl Schwarzschild (1873-1916) in the last years of his life, using the equations of Einstein's general theory of relativity, calculated the gravitational field around a mass of zero volume.) For the mass of the Sun, the Schwarzschild radius is 3 km, that is, to turn our The sun is in a black hole, you need to condense its entire mass to the size of a small town!

Inside the Schwarzschild radius, the theory predicts even stranger phenomena: all the matter of a black hole gathers into an infinitely small point of infinite density at its very center - mathematicians call such an object a singular perturbation. With an infinite density, any finite mass of matter, mathematically speaking, occupies zero spatial volume. Whether this phenomenon actually occurs inside a black hole, we, of course, cannot experimentally check, since everything that gets inside the Schwarzschild radius does not come back.

Thus, not having the opportunity to "examine" a black hole in the traditional sense of the word "look", we, nevertheless, can detect its presence by indirect signs of the influence of its super-powerful and completely unusual gravitational field on the matter around it.

Supermassive black holes

At the center of our Milky Way and other galaxies is an incredibly massive black hole millions of times heavier than the Sun. These supermassive black holes (as they got this name) were discovered by observing the nature of the movement of interstellar gas near the centers of galaxies. The gases, judging by the observations, rotate at a close distance from the supermassive object, and simple calculations using the laws of Newtonian mechanics show that the object that attracts them, with a meager diameter, has a monstrous mass. Only a black hole can spin the interstellar gas in the center of the galaxy this way. In fact, astrophysicists have already found dozens of such massive black holes in the centers of neighboring galaxies, and strongly suspect that the center of any galaxy is a black hole.

Stellar mass black holes

According to our current ideas about the evolution of stars, when a star with a mass exceeding about 30 solar masses perishes with a supernova explosion, its outer shell scatters, and its inner layers rapidly collapse towards the center and form a black hole in place of the star that has used up its fuel reserves. It is practically impossible to detect a black hole of this origin isolated in interstellar space, since it is located in a rarefied vacuum and does not manifest itself in any way in terms of gravitational interactions. However, if such a hole was part of a binary star system (two hot stars orbiting around their center of mass), the black hole will still exert a gravitational effect on its paired star. Astronomers today have more than a dozen candidates for the role of such stellar systems, although there is no strong evidence for any of them.

In a binary system with a black hole in its composition, the substance of the "living" star will inevitably "flow" in the direction of the black hole. And the substance sucked out by the black hole will swirl when falling into the black hole in a spiral, disappearing when crossing the Schwarzschild radius. When approaching the fatal boundary, however, the substance sucked into the black hole's funnel will inevitably thicken and heat up due to the increase in collisions between the particles absorbed by the hole until it heats up to the energies of wave radiation in the X-ray range of the electromagnetic spectrum. Astronomers can measure the periodicity of changes in the intensity of X-rays of this kind and calculate, by comparing it with other available data, the approximate mass of an object "pulling" matter onto itself. If the mass of an object exceeds the Chandrasekhar limit (1.4 solar masses), this object cannot be a white dwarf, in which our star is destined to degenerate. In most of the identified cases of observation of such binary X-ray stars, a neutron star is a massive object. However, more than a dozen cases have already been counted when the only reasonable explanation is the presence of a black hole in a binary star system.

All other types of black holes are much more speculative and based solely on theoretical research - there is no experimental evidence of their existence at all. First, these are black mini-holes with a mass comparable to the mass of a mountain and compressed to the radius of a proton. The idea of ​​their origin at the initial stage of the formation of the Universe immediately after the Big Bang was expressed by the English cosmologist Stephen Hawking (see The Hidden Principle of the Irreversibility of Time). Hawking suggested that mini-hole explosions could explain the truly mysterious phenomenon of chiseled gamma-ray bursts in the Universe. Secondly, some theories of elementary particles predict the existence in the Universe - at the micro-level - of a real sieve of black holes, which are a kind of foam from the wastes of the universe. The diameter of such micro-holes is supposedly about 10-33 cm - they are billions of times smaller than a proton. At the moment, we do not have any hopes for experimental verification of even the very fact of the existence of such black hole particles, let alone somehow investigating their properties.

And what happens to the observer if he suddenly finds himself on the other side of the gravitational radius, otherwise called the event horizon. This is where the most amazing property of black holes begins. It is not in vain that, speaking of black holes, we have always mentioned time, or rather space-time. According to Einstein's theory of relativity, the faster a body moves, the more its mass becomes, but the slower time begins to pass! At low speeds, under normal conditions, this effect is invisible, but if the body (spacecraft) moves at a speed close to the speed of light, then its mass increases, and time slows down! When the speed of the body is equal to the speed of light, the mass goes to infinity, and time stops! This is evidenced by rigorous mathematical formulas. Let's go back to the black hole. Imagine a fantastic situation when a spaceship with astronauts on board approaches the gravitational radius or event horizon. It is clear that the event horizon is so named because we can observe any events (generally observe something) only up to this border. That we are not able to observe this border. Nevertheless, being inside the spacecraft approaching the black hole, the astronauts will feel the same as before, because on their watch the time will run "normally". The spacecraft will calmly cross the event horizon and move on. But since its speed will be close to the speed of light, the spaceship will reach the center of the black hole, literally, in an instant.

And for an outside observer, the spacecraft will simply stop on the event horizon, and will stay there almost forever! This is the paradox of the colossal gravitation of black holes. A natural question is whether the astronauts who go to infinity according to the clock of an external observer will survive. No. And the point is not at all about the enormous gravitation, but about the tidal forces, which in such a small and massive body vary greatly at short distances. With the growth of an astronaut 1 m 70 cm, the tidal forces at his head will be much less than at his feet and he will simply be torn apart already on the event horizon. So, we have basically figured out what black holes are, but so far we have been talking about black holes of stellar mass. Currently, astronomers have managed to find supermassive black holes, the mass of which can be a billion suns! Supermassive black holes do not differ in properties from their smaller counterparts. They are only much more massive and, as a rule, are located in the centers of galaxies - the stellar islands of the Universe. In the center of Our Galaxy (Milky Way) there is also a supermassive black hole. The colossal mass of such black holes will make it possible to search for them not only in our Galaxy, but also in the centers of distant galaxies located at a distance of millions and billions of light years from the Earth and the Sun. European and American scientists have conducted a global search for supermassive black holes, which, according to modern theoretical calculations, should be located in the center of every galaxy.

Modern technologies make it possible to detect the presence of these collapsars in neighboring galaxies, but very few of them have been detected. This means that either black holes are simply hiding in dense gas and dust clouds in the central part of galaxies, or they are located in more distant corners of the Universe. So, black holes can be detected by X-rays emitted during the accretion of matter on them, and in order to make a census of such sources, satellites with X-ray telescopes on board were launched into near-Earth comic space. While searching for X-ray sources, the space observatories Chandra and Rossi found that the sky is filled with background X-rays and is millions of times brighter than visible light. Much of this background X-ray radiation from the sky must come from black holes. Usually in astronomy they talk about three types of black holes. The first is black holes of stellar masses (about 10 solar masses). They are formed from massive stars when they run out of thermonuclear fuel. The second is supermassive black holes in the centers of galaxies (masses from one million to billions of the sun). And finally, the primordial black holes formed at the beginning of the life of the Universe, the masses of which are small (of the order of the mass of a large asteroid). Thus, a large range of possible black hole masses remains unfilled. But where are these holes? While filling the space with X-rays, they nevertheless do not want to show their true "face". But in order to build a clear theory of the relationship between background X-ray radiation and black holes, you need to know their number. At the moment, space telescopes have managed to detect only a small number of supermassive black holes, the existence of which can be considered proven. Indirect signs allow us to bring the number of observed black holes responsible for background radiation to 15%. One has to assume that the rest of the supermassive black holes are simply hiding behind a thick layer of dust clouds that only transmit high-energy X-rays or are too far away to be detected by modern observing means.

Supermassive black hole (neighborhood) at the center of galaxy M87 (X-ray image). An ejection (jet) from the event horizon is visible. Image from the site www.college.ru/astronomy

Finding hidden black holes is one of the main challenges of modern X-ray astronomy. The latest breakthroughs in this area, associated with research with the Chandra and Rossi telescopes, nevertheless cover only the low-energy range of X-rays - approximately 2000-20,000 electron-volts (for comparison, the energy of optical radiation is about 2 electron-volts). volt). The European space telescope Integral, which is able to penetrate the still insufficiently studied region of X-rays with energies of 20,000-300,000 electron-volts, can make significant amendments to these studies. The importance of studying this type of X-rays is that although the X-ray background of the sky has a low energy, multiple peaks (points) of radiation with an energy of about 30,000 electron-volts appear against this background. Scientists are just opening the veil of the mystery of what gives rise to these peaks, and Integral is the first sufficiently sensitive telescope capable of finding such sources of X-rays. According to astronomers, high-energy rays give rise to the so-called Compton-thick objects, that is, supermassive black holes enveloped in a dusty shell. It is the Compton objects that are responsible for the 30,000 electron-volt X-ray peaks in the background radiation field.

But, continuing their research, scientists came to the conclusion that Compton objects make up only 10% of the number of black holes that should create high-energy peaks. This is a serious obstacle to the further development of the theory. So the missing X-rays are not coming from Compton-thick, but from ordinary supermassive black holes? Then what about the dust curtains for low energy X-rays? The answer seems to lie in the fact that many black holes (Compton objects) have had enough time to absorb all the gas and dust that enveloped them, but before that they had the opportunity to assert themselves with high-energy X-rays. After absorbing all the matter, such black holes were already unable to generate X-rays on the event horizon. It becomes clear why these black holes cannot be detected, and it becomes possible to attribute the missing sources of background radiation to their account, since although the black hole no longer emits, the radiation previously created by it continues its journey through the Universe. However, it is entirely possible that the missing black holes are more hidden than astronomers assume, that is, the fact that we do not see them does not mean that they are not at all. We just don't have enough observing power to see them. Meanwhile, NASA scientists plan to expand the search for hidden black holes even further into the universe. It is there that the underwater part of the iceberg is located, they say. For several months, research will be carried out as part of the Swift mission. Penetration into the deep universe will reveal hidden black holes, find the missing link for background radiation and shed light on their activity in the early era of the universe.

Some black holes are considered more active than their quiet neighbors. Active black holes absorb the surrounding matter, and if a "gape" star flying past gets into the flight of gravity, it will certainly be "eaten" in the most barbaric way (torn to shreds). The absorbed matter, falling on the black hole, heats up to enormous temperatures, and experiences a flash in the gamma, X-ray and ultraviolet ranges. There is also a supermassive black hole in the center of the Milky Way, but it is more difficult to study than holes in nearby or even distant galaxies. This is due to a dense wall of gas and dust that stands in the way of the center of our Galaxy, because the solar system is located almost at the edge of the galactic disk. Therefore, observing the activity of black holes is much more effective for those galaxies whose core is clearly visible. When observing one of the distant galaxies located in the constellation Bootes at a distance of 4 billion light years, astronomers for the first time managed to trace from the beginning and almost to the end the process of absorption of a star by a supermassive black hole. For thousands of years, this giant collapsar rested quietly in the center of an unnamed elliptical galaxy, until one of the stars dared to get close enough to it.

The black hole's powerful gravity tore the star apart. Clumps of matter began to fall on the black hole and, upon reaching the event horizon, flare up brightly in the ultraviolet range. These flares were recorded by the new NASA space telescope Galaxy Evolution Explorer, which studies the sky in ultraviolet light. The telescope continues to observe the behavior of the distinguished object even today. the black hole's meal is not over yet, and the remains of the star continue to fall into the abyss of time and space. Observing such processes will ultimately help to better understand how black holes evolve with their parent galaxies (or, conversely, galaxies evolve with their parent black hole). Earlier observations show that such excesses are not uncommon in the universe. Scientists have calculated that, on average, a star is absorbed by the supermassive black hole of a typical galaxy once every 10,000 years, but since there are a large number of galaxies, star absorption can be observed much more often.

a source

Despite the tremendous achievements in the field of physics and astronomy, there are many phenomena, the essence of which has not been fully disclosed. These phenomena include mysterious black holes, all information about which is only theoretical and cannot be verified in practice.

Do black holes exist?

Even before the advent of the theory of relativity, astronomers have expressed the theory of the existence of black funnels. After the publication of Einstein's theory, the question of gravity was revised and new assumptions appeared in the problem of black holes. It is unrealistic to see this cosmic object, because it absorbs all the light that enters its space. Scientists prove the existence of black holes by analyzing the movement of interstellar gas and the trajectory of the stars.

The formation of black holes leads to a change in the space-time characteristics around them. Time seems to be compressed under the influence of tremendous gravity and slows down. Stars caught in the path of the black funnel can deviate from their route and even change direction. Black holes absorb the energy of their twin star, which also manifests itself.

What does a black hole look like?

Most of the information regarding black holes is hypothetical. Scientists study them by their effects on space and radiation. It is not possible to see black holes in the universe, because they absorb all the light that enters the nearby space. An X-ray image of black objects was made from special satellites, on which a bright center is visible, which is the source of the radiation of the rays.

How do black holes form?

A black hole in space is a separate world that has its own unique characteristics and properties. The properties of cosmic holes are due to the reasons for their appearance. There are the following theories regarding the appearance of black objects:

1. They are the result of collapses occurring in space. It can be a collision of large cosmic bodies or a supernova explosion.
2. They arise due to the weighting of space objects while maintaining their size. The reason for this has not been determined.

A black funnel is an object in space that is relatively small in size with a huge mass. The black hole theory says that every cosmic object can potentially become a black funnel if, as a result of some phenomena, it loses its size, but retains its mass. Scientists even talk about the existence of many black microholes - miniature space objects with a relatively large mass. This mismatch between mass and size leads to an increase in the gravitational field and the appearance of a strong attraction.

What's in a black hole?

A black mysterious object can only be called a hole at a stretch. The center of this phenomenon is a cosmic body with increased gravity. The result of such gravity is a strong attraction to the surface of this cosmic body. In this case, a vortex flow is formed, in which gases and grains of cosmic dust rotate. Therefore, it is more correct to call a black hole a black funnel.

It is impossible to find out in practice what is inside a black hole, because the level of gravity of the cosmic funnel does not allow any object to escape from the zone of its influence. According to scientists, there is complete darkness inside the black hole, because the quanta of light disappear in it irrevocably. It is assumed that space and time are distorted inside the black funnel, the laws of physics and geometry do not apply in this place. Such features of black holes can presumably lead to the formation of antimatter, which is currently not familiar to scientists.

Why are black holes dangerous?

Sometimes black holes are described as objects that absorb surrounding objects, radiation and particles. This view is incorrect: the properties of a black hole allow it to absorb only what falls within its zone of influence. It can draw in cosmic microparticles and radiation emanating from twin stars. Even if the planet is near the black hole, it will not be absorbed, but will continue to move in its orbit.

What happens if you fall into a black hole?

The properties of black holes depend on the strength of the gravitational field. Black funnels attract everything that falls within their zone of influence. In this case, the space-time characteristics change. Scientists who study everything about black holes disagree about what happens to the objects in this funnel:

• some scientists assume that all objects falling into these holes are stretched or torn into pieces and do not have time to reach the surface of the attracting object;
• other scientists argue that all the usual characteristics are bent in holes, so objects there seem to disappear in time and space. For this reason, black holes are sometimes called gateways to other worlds.

Types of black holes

Black funnels are divided by types, based on the method of their formation:

1. Black objects of stellar masses are born at the end of the life of some stars. The complete combustion of the star and the end of thermonuclear reactions lead to the contraction of the star. If, however, the star undergoes a gravitational collapse, it will be able to transform into a black funnel.
2. Supermassive black funnels... Scientists argue that the core of any galaxy is a supermassive funnel, the formation of which is the beginning of the emergence of a new galaxy.
3. Primary black holes... This could include holes of varying masses, including microholes created by discrepancies in matter density and gravity. Such holes are funnels formed at the beginning of the birth of the Universe. This also includes objects such as a hairy black hole. These holes are distinguished by the presence of rays that look like hairs. It is assumed that these photons and gravitons store some of the information that falls into the black hole.
4. Quantum black holes... They appear as a result of nuclear reactions and live for a short time. Quantum funnels are of the greatest interest, since their study can help answer questions on the problem of black space objects.
5. Some scientists distinguish this type of space object, a hairy black hole. These holes are distinguished by the presence of rays that look like hairs. It is assumed that these photons and gravitons store some of the information that falls into the black hole.

The closest black hole to Earth

The nearest black hole is 3,000 light-years distant from Earth. It's called the V616 Monocerotis, or V616 Mon. Its weight reaches 9-13 solar masses. The binary partner of this hole is a star about half the mass of the Sun. Another funnel relatively close to Earth is Cygnus X-1. It is located 6 thousand light-years from the Earth and weighs 15 times more than the Sun. This black cosmic hole also has its binary partner, the movement of which helps to track the influence of Cygnus X-1.

Black holes - interesting facts

Scientists tell such interesting facts about black objects:

1. If we take into account that these objects are the center of galaxies, then in order to find the largest crater, the largest galaxy should be found. Therefore, the largest black hole in the universe is a funnel located in the galaxy IC 1101 in the center of the Abell 2029 cluster.
2. Black objects actually appear multi-colored. The reason for this lies in their radio-magnetic radiation.
3. There are no permanent physical or mathematical laws in the middle of a black hole. It all depends on the mass of the hole and its gravitational field.
4. The black funnels gradually evaporate.
5. The weight of black funnels can be incredible. The largest black hole has a mass of 30 million solar masses.

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

From the history of black holes

1783 g. The first hypothesis of 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 of Newton's creations - optics and mechanics. Michell's idea was this: if light is a stream of the smallest particles, then, like all other bodies, the particles should experience the attraction of the gravitational field. It turns out that the more massive the star, the more difficult it is for the light to resist its attraction. Thirteen years after Michell, the French astronomer and mathematician Laplace put forward (most likely independently of his British colleague) a similar theory.

1915 g. However, all their works remained unclaimed until the beginning of the 20th century. In 1915, Albert Einstein published General Relativity and showed that gravity is the 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 investigated the structure of curved spacetime around the Sun and rediscovered the phenomenon of black holes.

(John Wheeler introduced the term "Black Holes" into scientific use)

1967 year 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 year British physicist Stephen Hawking proved that black holes, while absorbing meteria without return, can emit radiation and eventually evaporate. This phenomenon is called Hawking radiation.

2013 g. The latest studies of pulsars and quasars, as well as the discovery of relic radiation, have finally made it possible to describe the very concept of black holes. In 2013, the gas cloud G2 approached a very close distance to a black hole and is likely to be absorbed by it, observing the unique process provides tremendous opportunities for new discoveries of the features of black holes.

(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 year... A group of scientists from the Event Horizon Telescope collaboration of several countries, having linked 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, with a diameter 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 true snapshot of a very distant object was obtained. Therefore, it took another two whole years to thoroughly process all the data and combine them into one whole.

Dec 2019 The data was successfully decoded and rendered into the first ever image of a black hole.

(The first ever snapshot 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 at the center of the object. The image was obtained as a result of interferometric observations with a very 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, pointing in the same direction.

What black holes really are

A laconic explanation of the phenomenon sounds like this.

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

The 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 energy supply 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 jet by a black hole at high speed


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


• 3. Black hole


• 4. Detailed diagram of the black hole region


• 5. Size of found new observations

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

Schwarzschild radius

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

• 1. Matter in motion at half the speed of light


• 2. Photon ring


• 3. Inner photonic ring


• 4. Event horizon in a black hole

Based on Einstein's General Theory of Relativity, if the body has approached the critical distance to the center of the hole, it will no longer be able to 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 substance of a black hole is concentrated in an infinitely small point, and in its center is an object with infinite density, which scientists call a singular perturbation.

How does a fall into a black hole happen?

(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 uncomplicated name G2, which emits unusual light. Such a glow can give rise to friction in gas and dust caused by the action of the Sagittarius A * black hole and which revolve around it in the form of an accretion disk. Thus, we become observers of the amazing phenomenon of absorption of a gas cloud by a supermassive black hole.

According to the latest studies, the closest approach to a black hole will occur in March 2014. We can recreate a picture of how this spectacular spectacle will take place.

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


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


• 3. It is expected that the cloud will pass by the black hole, but tidal forces caused by the difference in attraction acting on the leading and trailing edges of the cloud will cause it to take on an increasingly elongated shape.


• 4. After the cloud is broken apart, most of it is likely to flow into the accretion disk around Sagittarius A *, generating shock waves in it. At the same time, the temperature will jump 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 later, but it is expected that in the process of falling, it will emit powerful fluxes of X-rays, and no one else will see it.

Video: a black hole engulfs a gas cloud

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

What's inside the black hole

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

According to another theory, which 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 vibrations of strings on its surface, which is designated as the event horizon.

So what is an 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 seen at least somehow is in its immediate vicinity.

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

S. TRANKOVSKY

Among the most important and interesting problems of modern physics and astrophysics, Academician VL Ginzburg named questions related to black holes (see "Science and Life" Nos. 11, 12, 1999). The existence of these strange objects was predicted more than two hundred years ago, the conditions leading to their formation were accurately calculated at the end of the 30s of the XX century, and astrophysics came to grips with them less than forty years ago. Today, scientific journals around the world publish thousands of articles on black holes every year.

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

It is customary to depict the processes taking place in the vicinity of a collapsing black hole. With the passage of time (Y), the space (X) around it (the filled area) contracts, tending to the singularity.

The gravitational field of a black hole introduces strong distortions in the geometry of space.

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

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

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

HOW THEY ARISE

The luminous celestial body, which has a density equal to that of the Earth, and a diameter two hundred and fifty times the diameter of the Sun, because of the force of its attraction, will not allow its light to reach us. Thus, it is possible that the largest luminous bodies in the Universe, precisely because of their size, remain invisible.
Pierre Simon Laplace.
Outline of the system of the world. 1796 year.

In 1783, the English mathematician John Mitchell, and thirteen years later, independently of him, the French astronomer and mathematician Pierre Simon Laplace conducted a very strange study. They considered the conditions under which light would not be able to leave the star.

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

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

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

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

It is not difficult to calculate that the Sun (its mass is 2.1033 g) will turn into a black hole if it contracts to a radius of about 3 kilometers. The density of its substance will then reach 10 16 g / cm 3. The radius of the Earth, compressed to the state of a black hole, would decrease to about one centimeter.

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

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

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

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

And in the end, he turned out to be right: a thermonuclear reaction is really going on in the center of the star (another thing is that the so-called "standard solar model" based on the concept of thermonuclear fusion, apparently, turned out to be wrong - see, for example, Science and life "Nos. 2, 3, 2000). But nevertheless, the reaction in the center of the star passes, the star shines, and the radiation that arises during this process keeps it in a stable state. But the nuclear "fuel" in the star burns out. The release of energy stops, the radiation is extinguished, and the force restraining the gravitational attraction disappears. There is a limitation on the mass of a star, after which the star begins to irreversibly contract. Calculations show that this happens if the mass of the star exceeds two or three times the mass of the Sun.

GRAVITY COLLAPSE

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

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

But decreasing the frequency is equivalent to slowing down time, and when the frequency goes to zero, time stops. This means that an outside observer will see a very strange picture: the shell of a star, falling with increasing acceleration, instead of reaching the speed of light, stops. From his point of view, the compression will stop as soon as the size of the star approaches gravitational for the sake of
mustache. He will never see at least one particle "diving" under the Schwarzschiel sphere yes. But for a hypothetical observer falling into a black hole, everything will be over in a matter of moments on his watch. Thus, the time of the gravitational collapse of a star the size of the Sun will be 29 minutes, and a much denser and more compact neutron star - only 1 / 20,000 of a second. And here he is trapped by a nuisance associated with the geometry of space-time near the black hole.

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

SIZE OF BLACK HOLES

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

Apparently, it is these black holes that are found in the centers of galaxies. In any case, astronomers today number about fifty galaxies, in the center of which, judging by indirect signs (we will talk about them below), there are black holes with a mass of the order of a billion (10 9) solar. Our Galaxy, too, apparently has its own black hole; it was possible to estimate its mass quite accurately - 2.4. 10 6 ± 10% of the mass of the Sun.

The theory suggests that along with such supergiants, black mini-holes with a mass of about 10 14 g and a radius of about 10 -12 cm (the size of an atomic nucleus) should have appeared. They could appear in the first moments of the existence of the Universe as a manifestation of a very strong inhomogeneity of space-time at a colossal energy density. The conditions that were then in the Universe are now being implemented by researchers at powerful colliders (accelerators on colliding beams). Experiments at CERN, carried out earlier this year, made it possible to obtain quark-gluon plasma - matter that existed before the emergence of elementary particles. Research into this state of matter continues at Brookhaven, the American Accelerator Center. It is capable of accelerating particles to energies one and a half to two orders of magnitude higher than the accelerator in
CERN. The experiment that is being prepared has caused serious concern: will not a black mini-hole appear during its implementation, which will bend our space and destroy the Earth?

This fear caused such a strong resonance that the US government was forced to convene an authoritative commission to test this possibility. The commission, which consisted of prominent researchers, concluded that the energy of the accelerator is too low for a black hole to appear (this experiment is described in the journal "Science and Life" No. 3, 2000).

HOW TO SEE THE INVISIBLE

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

1. It is necessary to trace the rotation of stars in clusters around a certain center of gravity. If it turns out that there is nothing in this center, and the stars revolve, as it were, around an empty space, we can confidently say that there is a black hole in this "emptiness". It was on this basis that the presence of a black hole in the center of our Galaxy was assumed and its mass was estimated.

2. The black hole is actively sucking in matter from the surrounding space. Interstellar dust, gas, matter of nearby stars fall on it in a spiral, forming the so-called accretion disk, similar to Saturn's ring. (This is exactly what scared the Brookhaven experiment: a black mini-hole formed in the accelerator will begin to suck the Earth into itself, and this process could not be stopped by any forces.) Approaching the Schwarzschild sphere, the particles undergo acceleration and begin to emit in the X-ray range. This radiation has a characteristic spectrum similar to the well-studied radiation of particles accelerated in a synchrotron. And if such radiation comes from some area of ​​the Universe, it is safe to say that there must be a black hole.

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

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

There is, however, black holes and one more property predicted theoretically, which, perhaps, would allow them to be seen. But, however, on one condition: the mass of the black hole must be much less than the mass of the Sun.

BLACK HOLE MAY BE "WHITE"

For a long time, black holes were considered the embodiment of darkness, objects that in a vacuum, in the absence of absorption of matter, do not emit anything. However, in 1974, the famous English theorist Stephen Hawking showed that temperature can be attributed to black holes, and, therefore, they must radiate.

According to the concepts of quantum mechanics, vacuum is not a void, but a kind of "foam of space-time", a jumble of virtual (unobservable in our world) particles. However, quantum energy fluctuations are capable of "throwing" a particle-antiparticle pair out of the vacuum. For example, when two or three gamma quanta collide, an electron and a positron will appear as if out of nothing. This and similar phenomena have been observed many times in laboratories.

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

Hawking calculated the rates at which all these processes are going, and came to the conclusion: the probability of absorption of particles with negative energy is higher. This means that the black hole loses energy and mass - it evaporates. In addition, it radiates as an absolutely black body with a temperature T = 6 . 10 -8 M with / M kelvin, where M s is the mass of the Sun (2.10 33 g), M is the mass of the black hole. This simple relationship shows that the temperature of a black hole with a mass six times the solar mass is equal to one hundred millionth of a degree. It is clear that such a cold body practically does not radiate anything, and all the above reasoning remains valid. Mini-holes are a different matter. It is easy to see that with a mass of 10 14 -10 30 grams, they turn out to be heated to tens of thousands of degrees and white-hot! However, it should be noted right away that there is no contradiction with the properties of black holes: this radiation is emitted by a layer above the Schwarzschild sphere, and not below it.

So, a black hole, which seemed to be a frozen object forever, sooner or later disappears, evaporating. Moreover, as it "loses weight", the rate of evaporation increases, but it still takes an extremely long time. It is estimated that mini-holes weighing 10 14 grams, which appeared immediately after the Big Bang 10-15 billion years ago, should have completely evaporated by now. At the last stage of their life, their temperature reaches colossal values; therefore, the products of evaporation must be particles of extremely high energy. It is possible that it is they that give rise to wide amospheric showers in the Earth's atmosphere - EAS. In any case, the origin of particles of anomalously high energy is another important and interesting problem that can be closely related to the equally exciting questions of the physics of black holes.