Black hole in space: where does it come from. Why is a black hole black Reaction to emitted light

A supermassive body of four million solar masses has been discovered near the center of our galaxy. True, it is invisible, inaudible and intangible.

Finger to the sky?

A group of German physicists from the Max Planck Institute for Extraterrestrial Physics recently made a sensational statement: they have obtained evidence that there is a black hole in our galaxy.
- For about twenty years, we have been observing the movement of several dozen stars near the center of the Galaxy, located at a distance of 27 thousand light years from the Sun, - says the head of the group, Reinhard Genzel. - The orbits of these stars indicate that the concentration of mass located in the center is, without a doubt, a black hole.
Does this threaten our Galaxy? Will the space monster eat the Earth?
It turned out that there are no answers to these questions yet. According to the director of the State Astronomical Institute. P. K. Sternberg of Moscow State University, Corresponding Member of the Russian Academy of Sciences Anatoly Cherepashchuk, observing the orbits, a black hole cannot be calculated.
- To prove that the body located in the center of our Galaxy is a black hole, you need to do two things, - the scientist explained to reporters. - First, experimentally show that the radius of this body is equal to the so-called gravitational radius for a black hole of a given mass (and for a black body of four million solar masses, it is approximately seven solar radii). And, secondly, to prove that this body does not have a solid surface, but instead an event horizon.
According to Cherepashchuk, both of these tasks are in principle feasible, and in 20 years, he hopes, scientists will be able to say for sure whether this is a black hole or not.
In general, the question: to be or not to be our Galaxy - is postponed for two decades. In the meantime, let's get to know this monster better.

The ugliest place

There is no more mysterious and frightening object in space than a black hole. One phrase already inspires unaccountable fear: it draws the image of an all-consuming abyss. Before her, not only the townsfolk are shy, but also astrophysicists tremble. “Of all the creations of the human mind, from mythological unicorns and dragons to the hydrogen bomb, perhaps the most fantastic is the black hole. A hole in space with very specific edges, into which anything can fall and from which nothing can get out. A hole in which the gravitational force is so great that even light is captured and held in this trap. A hole that warps space and distorts the flow of time. Like unicorns and dragons, black holes seem more like science fiction or ancient myths than real objects. However, the existence of black holes inevitably follows from physical laws. In our Galaxy alone, there may be millions of them, ”said Kip Stephen Thorne, a well-known scientist, head of the department at the California Institute of Technology (USA), a member of the US National Academy of Sciences, a member of the NASA Academic Council, about black holes.
In addition to their fantastic power, black holes have an amazing ability to change space and time within themselves. They first twist into a kind of funnel, and then, having crossed a certain boundary in the depths of the hole, they disintegrate into quanta. Inside the black hole, beyond the edge of this peculiar gravitational abyss, from which there is no way out, amazing physical processes flow, new laws of nature are manifested.
According to many experts, black holes are the most grandiose sources of energy in the universe. We probably see them in distant quasars, in exploding galactic nuclei. It is assumed that black holes in the future will become energy sources for mankind.

The end of the world is here

How are black holes formed? According to astrophysicists, most of them arise after the death of large stars. If the mass of a star is twice that of the sun, then by the end of its life the star may explode as a supernova. But if the mass of matter left after the explosion still exceeds two solar masses, then the star should shrink into a tiny dense body, since gravitational forces completely suppress any internal resistance to compression. Scientists believe that it is at this moment that a catastrophic gravitational collapse leads to the emergence of a black hole. They believe that with the end of thermonuclear reactions, the star can no longer be in a stable state. Then there is one inevitable path left for a massive star - the path of general and complete compression, turning it into an invisible black hole.

Why are they invisible?

The very name "black holes" suggests that this is a class of objects that cannot be seen, - explains the head of the radio astronomy department of the State Astronomical Institute. Sternberg Candidate of Physical and Mathematical Sciences Valentin Esipov. - Their gravitational field is so strong that if somehow it was possible to get close to a black hole and direct the beam of the most powerful searchlight away from its surface, then this searchlight would not be visible even from a distance not exceeding the distance from the Earth to the Sun.
Indeed, even if we were able to concentrate all the light of the Sun in this powerful searchlight, we would not see it, since the light could not overcome the influence of the gravitational field of the black hole on it and leave its surface. That is why such a surface is called the absolute event horizon. It represents the boundary of a black hole. And what is hiding there, abroad?

Let's walk to Hell

The most interesting description of the “inside” of a black hole belongs to the American physicist and astronomer Kip Stephen Thorne, whom we have already mentioned. “Imagine you are the captain of a large star-class spaceship. suggests the scientist in his book Journey Among Black Holes. - On the instructions of the Geographical Society, you have to explore several black holes located at large distances from each other in interstellar space, and using radio signals to transmit a description of your observations to Earth,
After being on the road for 4 years and 8 months, your ship slows down in the vicinity of the black hole closest to Earth, called Hades (Hell) and located near the star Vega. The presence of a black hole is noticeable on the television screen: hydrogen atoms scattered in interstellar space are drawn in by its gravitational field. Everywhere you see them move: slowly away from the hole and faster as you get closer to it. It's like water falling in Niagara Falls, except that the atoms are falling not only from the east, but also from the west, north, south, above and below - everywhere. If you do nothing, you too will be drawn inward.
So, you have to use the greatest care to transfer the starship from the trajectory of free fall into a circular orbit around the black hole (similar to the orbits of artificial satellites revolving around the Earth) so that the centrifugal force of your orbital motion compensates for the black hole's gravity. Feeling safe, you turn on the ship's engines and prepare to explore the black hole.
First of all, in telescopes, you observe electromagnetic radiation emitted by falling hydrogen atoms. Far from the black hole, they are so cold that they emit only radio waves. But closer to the hole, where the atoms fall faster, they occasionally collide with each other, heat up to several thousand degrees and begin to emit light. Even closer to the black hole, moving much faster, they are heated by collisions to several million degrees and emit X-rays.
By pointing your telescopes "in" and continuing to approach the black hole, you will "see" the gamma rays emitted by hydrogen atoms heated to even higher temperatures. And finally, in the very center, you will find the dark disk of the black hole itself.
Your next step is to carefully measure the length of the ship's orbit. This is approximately 1 million km, or half the length of the Moon's orbit around the Earth. Then you look at the distant stars and see that they move like you. Watching their apparent movement, you find out that you need 5 minutes. 46 s to make one revolution around the black hole. This is your "orbital period".
Knowing the period of revolution and the length of your orbit, you can calculate the mass of the black hole Hades (Hell). It will be 10 times larger than the sun. This is essentially the total mass that has accumulated in a black hole over its entire history and includes the mass of a star that collapsed to form a black hole about 2 billion years ago, the mass of all interstellar hydrogen drawn into it since its birth, and also the mass of all the asteroids and stray starships that fell on it.
The most interesting properties of its surface, or horizon - the border, because of which everything that falls into the hole can no longer return. Borders, because of which a starship and even any kind of radiation cannot escape: radio waves, light, x-rays or gamma rays ...
Although you can calculate all the properties of a black hole from the outside of a black hole from its mass and angular momentum, you can't learn anything about its inside. It may have a disordered structure and be highly asymmetric. All this will depend on the details of the collapse that formed the black hole, as well as on the features of the subsequent retraction of interstellar hydrogen, so the diameter of the hole simply cannot be calculated.
With these results, you can explore the vicinity of the black hole's horizon...
After saying goodbye to the crew, you climb into the descent vehicle and leave the ship, remaining first in the same circular orbit, physicist Thorne continues. - Then, turning on the rocket engine, slow down slightly to slow down your orbital movement. At the same time, you begin to spiral towards the horizon, moving from one circular orbit to another. Your goal is to enter a circular orbit with a perimeter slightly greater than the length of the horizon. As you move in a spiral, the length of your orbit is gradually reduced - from 1 million km to 500 thousand, then to 100 thousand, 90 thousand, 80 thousand. And then something strange begins to happen.
Being in a state of weightlessness, you are suspended in your apparatus, let's say, with your feet - to the black hole, and your head - to the orbit of your ship and the stars. But gradually you begin to feel that someone is pulling your legs down and up - behind your head. You realize that the reason is the black hole's attraction: the legs are closer to the hole than the head, so they are attracted more strongly. The same is true, of course, on Earth, but the difference in the attraction of the legs and head is negligible there, so no one notices it. Moving in an orbit 80,000 km long above a black hole, you feel this difference quite clearly - the difference in attraction will be 1/8 of the earth's gravity (1/8 g). The centrifugal force due to your movement in orbit compensates for the attraction of a hole in the central point of your body, allowing you to freely float in weightlessness, but an excess attraction of 1/16 g will act on your legs, on the contrary, your head will be attracted weakly, and the centrifugal force will pull it up with exactly the same additional acceleration -1/16 g.
Somewhat bewildered, you continue your spiral, but surprise quickly turns to worry: as the orbit shrinks, the forces pulling you will increase more and more rapidly. With an orbit length of 64 thousand km, the difference will be 1/4 g, at 51 thousand km - 1/2 g and at 40 thousand km it will reach the full earth's weight. Gritting your teeth from the effort, you continue to move in a spiral. With an orbit length of 25 thousand km, the stretching force will be 4 g, i.e. four times your weight on earth, and at 16 thousand km -16 g. You are no longer able to stand upright. You try to solve this problem by curling up and pulling your legs up to your head, thereby reducing the difference in forces. But they are already so large that they will not let you bend - they will again be stretched vertically (along the direction that is radial with respect to the black hole).
Whatever you do, nothing will help. And if the spiral continues, your body will not stand it - it will be torn apart. So there is no hope of reaching the vicinity of the horizon...
Shattered, overcoming monstrous pain, you stop your descent and transfer the device first into a circular orbit, and then begin to carefully and slowly move along an expanding spiral, moving into circular orbits of ever larger size, until you reach the starship.
Thorne's story sounds like science fiction so far. And it is designed for the time when a person will achieve such success in the development of technology and technology that intergalactic flights and the construction of ring worlds around black holes will become a reality. And according to the most optimistic forecasts of futurologists, this will be possible no earlier than in 50 years.

No guys, it's not like that...

It must be admitted that many scientists still deny the existence of black holes. After all, their discovery and study takes place at the tip of the pen. And recently, an even more unexpected assumption has appeared that black holes are not holes at all, but some objects that are more akin in nature to the bubbles of the Bose-Einstein condensate (an aggregate state of matter, which is based on bosons cooled to temperatures close to absolute zero). This new hypothesis was proposed by researcher Emil Mottola of the Theoretical Division of Los Alamos National Laboratory, together with co-author Pavel Mazur of the University of South Carolina in the USA.
The researchers' explanation introduces a radically new look at the nature of black holes, which are presented not as "holes" in space, where matter and light inexplicably disappear into the event horizon zone, but rather as spherical voids surrounded by a special form of matter never before known on Earth. Mazur and Mottola call these objects not black holes, but gravitational stars.
Inside the gravitational star, space and time are reversed, just like in the black hole model.
Mottola and Mazur even suggest that the universe we live in could be the inner shell of a giant gravitational star. Author: S.Kuzmina

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 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, but from the above it can be assumed that the astronaut will fall into the black hole very slowly and may simply not live to see the moment when his body begins to deform.

It is noteworthy that for an observer outside, all bodies that have flown up to the event horizon will remain at the edge of this horizon until their image disappears. The reason for this phenomenon is the gravitational redshift. Simplifying somewhat, we can say that the light falling on the body of a suicide astronaut "frozen" at the event horizon will change its frequency due to its slowed down time. As time passes more slowly, the frequency of light will decrease and the wavelength will increase. As a result of this phenomenon, at the output, that is, for an external observer, the light will gradually shift towards the low-frequency - red. A shift of light along the spectrum will take place, as the suicide astronaut moves further and further away from the observer, albeit almost imperceptibly, and his time flows more and more slowly. Thus, the light reflected by his body will soon go beyond the visible spectrum (the image will disappear), and in the future the astronaut's body can be caught only 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 the light will no longer be able to move away from it. That is, roughly speaking, the light begins to "fall" into the "pit", which does not even have a "bottom".

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

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

Detection methods

Consider the methods that astronomers use to detect a black hole:

In addition to the methods mentioned above, scientists often associate objects such as black holes and. Quasars are some 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 BH and the accretion disk, and are not emitted by a direct black hole.

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

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

Merging and colliding black holes

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

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

How do black holes die?

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

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

Despite the mechanism proposed by Hawking for the destruction of black holes, the properties of Hawking radiation cause a paradox in the framework of quantum mechanics. If a black hole absorbs some body, and then loses the mass resulting from the absorption of this body, then regardless of the nature of the body, the black hole will not differ from what it was before the absorption of the body. In this case, information about the body is forever lost. From the point of view of theoretical calculations, the transformation of the initial pure state into the resulting mixed (“thermal”) state does not correspond to the current theory of quantum mechanics. This paradox is sometimes called the disappearance of information in a black hole. A real solution to this paradox has never been found. Known options for solving the paradox:

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

Unsolved problem of black hole physics

Judging by everything that was described earlier, black holes, although they have been studied for a relatively long time, still have many features, the mechanisms of which are still not known to scientists.

• In 1970, an English scientist formulated the so-called. "principle of cosmic censorship" - "Nature abhors the bare singularity." This means that the singularity is formed only in places hidden from view, like the center of a black hole. However, this principle has not yet been proven. There are also theoretical calculations according to which a "naked" singularity can occur.
• The “no-hair theorem”, according to which black holes have only three parameters, has not been proven either.
• A complete theory of the black hole magnetosphere has not been developed.
• The nature and physics of the gravitational singularity has not been studied.
• It is not known for certain what happens at the final stage of the existence of a black hole, and what remains after its quantum decay.

Interesting facts about black holes

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

• Black holes have only three parameters: mass, electric charge and angular momentum. As a result of such a small number of characteristics of this body, the theorem stating this is called the "no-hair theorem". This is also where the phrase “a black hole has no hair” came from, which means that two black holes are absolutely identical, their three parameters mentioned are the same.
• The density of black holes can be less than the density of air, and the temperature is close to absolute zero. From this we can assume that the formation of a black hole occurs not due to the compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume.
• Time for bodies absorbed by black holes goes much slower than for an external observer. In addition, the absorbed bodies are significantly stretched inside the black hole, which has been called spaghettification by scientists.
• There may be about a million black holes in our galaxy.
• There is probably a supermassive black hole at the center of every galaxy.
• In the future, according to the theoretical model, the Universe will reach the so-called era of black holes, when black holes will become the dominant bodies in the Universe.

Black holes are the only cosmic bodies capable of attracting light by gravity. They are also the largest objects in the universe. We're not likely to know what's going on near their event horizon (known as the "point of no return") anytime soon. These are the most mysterious places of our world, about which, despite decades of research, very little is known so far. This article contains 10 facts that can be called the most intriguing.

Black holes don't suck in matter.

Many people think of a black hole as a kind of "cosmic vacuum cleaner" that draws in the surrounding space. In fact, black holes are ordinary cosmic objects that have an exceptionally strong gravitational field.

If a black hole of the same size arose in the place of the Sun, the Earth would not be pulled inward, it would rotate in the same orbit as it does today. Stars located near black holes lose part of their mass in the form of stellar wind (this happens during the existence of any star) and black holes absorb only this matter.

The existence of black holes was predicted by Karl Schwarzschild

Karl Schwarzschild was the first to apply Einstein's general theory of relativity to justify the existence of a "point of no return". Einstein himself did not think about black holes, although his theory makes it possible to predict their existence.

Schwarzschild made his suggestion in 1915, just after Einstein published his general theory of relativity. That's when the term "Schwarzschild radius" came about, a value that tells you how much you have to compress an object to make it a black hole.

Theoretically, anything can become a black hole, given enough compression. The denser the object, the stronger the gravitational field it creates. For example, the Earth would become a black hole if an object the size of a peanut had its mass.

Black holes can spawn new universes

The idea that black holes can spawn new universes seems absurd (especially since we are still not sure about the existence of other universes). Nevertheless, such theories are being actively developed by scientists.

A very simplified version of one of these theories is as follows. Our world has exceptionally favorable conditions for the emergence of life in it. If any of the physical constants changed even slightly, we would not be in this world. The singularity of black holes overrides the usual laws of physics and could (at least in theory) give rise to a new universe that would be different from ours.

Black holes can turn you (and anything) into spaghetti

Black holes stretch objects that are close to them. These objects begin to resemble spaghetti (there is even a special term - "spaghettiification").

This is due to the way gravity works. At the moment, your feet are closer to the center of the Earth than your head, so they are being pulled more strongly. At the surface of a black hole, the difference in gravity starts to work against you. The legs are attracted to the center of the black hole faster and faster, so that the upper half of the torso cannot keep up with them. Result: spaghettification!

Black holes evaporate over time

Black holes not only absorb the stellar wind, but also evaporate. This phenomenon was discovered in 1974 and was named Hawking radiation (after Stephen Hawking, who made the discovery).

Over time, the black hole can give all its mass into the surrounding space along with this radiation and disappear.

Black holes slow down time around them

As you get closer to the event horizon, time slows down. To understand why this happens, one must turn to the "twin paradox," a thought experiment often used to illustrate the basic tenets of Einstein's general theory of relativity.

One of the twin brothers remains on Earth, while the other flies off on a space journey, moving at the speed of light. Returning to Earth, the twin finds that his brother has aged more than he, because when moving at a speed close to the speed of light, time passes more slowly.

As you approach the event horizon of a black hole, you will be moving at such a high speed that time will slow down for you.

Black holes are the most advanced power plants

Black holes generate energy better than the Sun and other stars. This is due to the matter revolving around them. Overcoming the event horizon at great speed, the matter in the orbit of a black hole is heated to extremely high temperatures. This is called blackbody radiation.

For comparison, during nuclear fusion, 0.7% of matter is converted into energy. Near a black hole, 10% of matter becomes energy!

Black holes warp space around them

Space can be thought of as a stretched rubber band with lines drawn on it. If you put an object on the plate, it will change its shape. Black holes work the same way. Their extreme mass attracts everything to itself, including light (the rays of which, continuing the analogy, could be called lines on a plate).

Black holes limit the number of stars in the universe

Stars arise from gas clouds. In order for star formation to begin, the cloud must cool.

Radiation from black bodies prevents gas clouds from cooling and prevents the formation of stars.

Theoretically, any object can become a black hole.

The only difference between our Sun and a black hole is the strength of gravity. It is much stronger at the center of a black hole than at the center of a star. If our Sun were compressed to about five kilometers in diameter, it could be a black hole.

Theoretically, anything can become a black hole. In practice, we know that black holes arise only as a result of the collapse of huge stars, exceeding the mass of the Sun by 20-30 times.

These mysterious black holes.
A black hole is a region of space that attracts matter that is within its reach and does not let anything out, not even light. The reason why this "hole" is called black is that it "sucks in" all the light that enters its boundaries (the so-called "event horizon") and does not reflect anything back. Although little is known about black holes, scientists have developed their own theories about their properties and structure.

1. Black holes affect time

When time slows down.

In the same way that clocks run a little slower at sea level than on a space station, they run very slowly near black holes. It has to do with the action of gravity.

2. The nearest black hole is 1,600 light-years away from Earth

space distances.

Our galaxy is full of black holes. Even at the center of the Milky Way, at a distance of 30,000 light-years from Earth, there is a giant black hole that is more than 30 million times larger than the Sun. But the chance that one of them will destroy the solar system is very small - because they are very far away.

3. Black holes eventually evaporate

Cycle of holes in nature.

While it is common knowledge that nothing can escape a black hole, there is at least one exception: radiation. According to some scientists, as black holes emit radiation, they lose mass. This process may eventually kill the black hole.

4. Black holes are not infinitesimal

When size matters.

At some point, the collapsing core of a black hole becomes smaller than an atom or an electron. But it eventually reaches the Planck length, the quantum size limit, and this leads to the fact that it becomes impossible to measure.

5. The shape of a black hole is not a funnel, but a sphere

Funnel, but not a sphere.

In most textbooks, you can see the image of a black hole in the form of a funnel. This is to illustrate them in terms of the "gravity well" that they are. In fact, they are more like spheres.

6. Rotation of a black hole

And yet she spins!

As the core of a star collapses, the star spins faster and faster and becomes smaller and smaller. When it reaches a point where it doesn't have enough mass to become a black hole, it collapses to form a neutron star and continues to spin rapidly. The same applies to black holes. Even when a black hole shrinks to the Planck length, it continues to spin rapidly.

7 Things Get Weird Around A Black Hole

Distorting space and time

Black holes have the ability to warp space itself. And, as they continue to rotate, the distortion is also distorted. This is an infinite regression of distortions.

8. A black hole can kill a person in a creepy way.

killing holes
While it seems obvious that a black hole is simply incompatible with life, most people think they'll just be crushed. This is not necessarily the case. A person is likely to be stretched to death and torn apart, as the part of their body that first reaches the event horizon will be the first to encounter the terrifying force of gravity.

9. Black holes are not necessarily destructive.

Are black holes useful?

Of course, in most cases, they simply destroy everything they “reach out to”. However, there are numerous theories and suggestions that black holes can actually be used for energy and space travel.

10. Black holes can get huge.

Black holes can get huge

Although it has just been argued that black holes are small, this is not always the case. They get bigger and bigger as they collide with other black holes, allowing their size to increase with each collision.

11. There are different types of black holes.

Such different holes.

Modern astronomers claim that there are actually various variations of black holes. There are spinning black holes, electric black holes, and spinning electric black holes. The type of black hole depends on the amount of energy they emit when they warp space.

12 Albert Einstein Was Not The First Person To Discover Black Holes

Albert Einstein and the theory of black holes.

Albert Einstein only revived the theory of black holes in 1916. Long before that, in 1783, a scientist named John Mitchell developed a theory about whether the force of gravity could be so strong that even light particles could not escape it.

13. Black holes can be very dense.

Heavier than the sun.

In order to have enough gravity to even attract light, a black hole must contain an incredible amount of mass in a very small space. This means that black holes should have a mass of about 10 to 30 billion times the mass of the Sun.

14. Black holes can create the elements that make life possible.

The place where life originated?

The researchers say that black holes create elements when they break down matter into subatomic particles. These particles have the ability to create elements heavier than helium, such as iron and carbon, as well as many others that are essential to the formation of life.

15. The laws of physics are violated at the center of a black hole.

And no laws of physics!

According to the main theory, the matter inside the black hole is “compressed” to an infinite density, and space and time also cease to exist. When this happens, the laws of physics simply stop working, because under normal conditions, nothing exists with zero volume and infinite density.

Space is full of mysteries. A black hole is one of the most amazing cosmic phenomena. Despite the fact that it is still little studied, scientists have discovered a number of interesting facts about black holes.

Space holds many mysteries. One of the most fascinating of these is black holes. Although there are still many unanswered questions about black holes, scientists have discovered many interesting things about them.

Why are black holes black?

Black holes do not reflect light, and color, in turn, is the result of light reflection. This phenomenon is of a natural nature, so we perceive various objects in red, blue or green.

Why do black holes appear black?

Color is an effect of light reflection - a natural phenomenon. It is why we perceive some things as red, some as blue, and others as green. Black holes do not reflect light.

Why are black holes holes?

Gravity helps us walk on the Earth, on the Moon it is 6 times weaker. That's why we watch astronauts "hover" in the air. Black holes have very powerful gravity; so powerful that an object can disappear if it hits them.

Why are they holes?

On Earth, gravity helps us stay grounded. On the moon, for example, there is very low gravity. That is astronauts can jump very high on the moon. Black holes have very strong gravity – so strong that no object can escape being sucked into it.

How did black holes appear?

In fact, black holes are extinct stars. However, only those stars become black holes, the mass of which after the explosion exceeds the mass of the Sun. Don't worry: the Sun, the star at the center of our solar system, won't turn into a black hole.

How do black holes come into existence?

One way black holes form is from gravitational collapse. When stars run out of fuel, they die, collapsing in on themselves. If these stars have a very large mass, they form black holes.

Is there a way to see a black hole?

Black holes are very difficult to observe because they do not reflect light. However, scientists have managed to find several solutions to this problem: a black hole can be seen when particles fall into it, at which point a lot of energy is released; it can also be detected by the movement of objects around the black hole, since the orbits of objects will change.

Is there any way to spot a black hole?

Because they do not reflect light, black holes are very difficult to observe. But scientists have found a solution. Black holes can be noticed when particles fall into them. Because a lot of energy is created when this happens, it can be detected. Black holes can also be discovered by observing the movement of other objects around them. The direction of their orbit changes when they are near a black hole.

Do black holes change in size?

Yes, they do. There are four types of black holes: small, stellar, intermediate mass, and supermassive.

If black holes attract other stars or merge with other black holes, they become huge. Such giants are called supermassive black holes. Scientists claim that there is such a supermassive black hole at the center of the Milky Way of our galaxy.

Do black holes differ in size?

Yes, they do. There are four types of black holes: micro, stellar, intermediate mass and supermassive. If black holes attract many stars or combine with other black holes, they become very big. These are called supermassive black holes. Scientists say there is a supermassive black hole at the center of the Milky Way, our galaxy.

Can black holes disappear?

Scientists believe that black holes "evaporate" very slowly, emitting particles. But this is happening so slowly that it has not been possible to see it yet.

Can black holes disappear?

A theory claims that yes, they can disappear due to radiation. But this has not been proven yet.

We still do not know so much about space, and scientists are actively working to discover new interesting facts. Perhaps it is you who will become the scientist who will answer all the questions about space!

There are many things we don't know about space, and scientists are still working on discovering new and interesting things. Maybe you will become a scientist and be the one to find answers to these questions!