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

How not to get lost in the diversity of the flow of words from little whys? After all, children are extremely curious and want to know everything in the world. It is worth properly instilling in them knowledge and a love of science, so that in the future they will find it easier to study and have an interest in new knowledge, especially such amazing things as space!

1. What is astronomy and space?

First of all, it’s worth starting by telling your child what astronomy is. After all, this is where, in essence, the study of stars and space begins.

Astronomy is a science that deals not only with stars, but also studies space and all the particles that move in the Universe. The scope of its study includes changes and transformations that occur with all celestial bodies, space and time.

By the way, the word "space" has Greek roots and means the orderliness and interconnection of everything that is in the Universe.

2. Solar system.

solar system consists of nine planets and one star. All nine planets revolve around a star called the Sun.

The planets have their own names: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. The very first, Venus, is closest to the sun, the last, Pluto, is farthest from the star. Planet Earth, on which we live, is the third.

In addition to the planets in solar system Many satellites, comets, small planets, asteroids, dust and gas also rotate.

3. Galaxy.

Galaxies- are large star systems in which the stars are kept within their boundaries due to gravity.

Scientists believe that there are billions of galaxies. Therefore, the likelihood that there is some kind of life somewhere on other planets and people in this world are not alone is very high.

All galaxies differ from each other in shape. There are only three shapes: elliptical, spiral and irregular.

By the way, our galaxy is called Milky Way. There are also two other large galaxies nearby called Andromeda and Triangulum. Our galaxy is part of a group of 30 other galaxies.

4. Black holes.

A black hole is a region in space-time that has the property of absorbing nearby objects, even those moving at the speed of light.

To explain to a child the effect of a Black Hole, you can compare it to a vacuum cleaner. The principle of operation is approximately the same, with the only difference being that Black holes do not use suction, but gravity to attract cosmic particles to themselves.

What are black holes?

Children, do you think you could ever see the effect of a vacuum in your room? When you do something, watch carefully because you may see dirt and crumbs start to move towards the vacuum cleaner. A black hole is like a vacuum cleaner, but only in space. However, it is not the powerful suction that causes things to fall into the black hole. The suction will not be strong enough. Instead, the black hole uses gravity to pull in everything around it.

How are black holes formed? Explanation for children

When big stars running out of fuel, she can no longer support her weight. Pressure from massive layers of hydrogen causes the star to shrink smaller and smaller. Eventually, the star will become smaller than an atom. Imagine, children, for a moment that the entire star will be crushed into a point smaller than an atom.

How can something be smaller, but retain the same amount of mass?

It's actually very simple. Take a bottle-sized sponge, you can easily crush it in your hands. But here's an interesting point. If you do anything less by squeezing it, its gravity becomes stronger. Imagine kids, if you compress a star into the size of an atom, how powerful will its gravity become?

The gravity of a black hole is so powerful that it absorbs everything, even light that passes too close. That's right, even light can't escape a black hole.

The structure of a black hole. Astronomy for children

Black holes are made up of three main parts. The outer layer of a black hole is called the outer event horizon. Inside outer horizon events, you can still escape from the gravity of a black hole, because the force of gravity here is not so strong. Middle layer of a black hole is called the inner event horizon. If you didn't escape the black hole's gravity before you entered the inner event horizon, then you kids missed your chance. The force of gravity in this layer is much stronger and does not let go of the objects it grabs. At this point, you begin to fall towards the center of the black hole. The center of a black hole is called the Singularity. This strange word means a crushed star. The singularity is the place where the black hole's gravity is strongest.

How can you get into a black hole?

Think about the Earth. If you get too close to the Earth, you run into its gravity. On Earth, you could fly into space on a rocket again. However, if you fall into a black hole, then you children have no way to get out, since gravity is very strong.

You've probably seen science fiction films, where the heroes, traveling through space, find themselves in another universe? Most often, mysterious cosmic black holes become the door to another world. It turns out there is some truth to these stories. Scientists say so.

When the very center of a star - in its core - runs out of fuel, all its particles become very heavy. And then, the entire planet collapses into its center. This causes a powerful shock wave, which tears the outer, still burning, shell of the star and it explodes in a blinding flash. One teaspoon of a small extinct star weighs several billion tons. Such a star is called neutron. And if a star is twenty to thirty times larger than our sun, its destruction leads to the formation of the strangest phenomenon in the universe - black hole.

The gravity in a Black Hole is so strong that it traps planets, gases and even light. Black holes are invisible, they can only be found by a huge funnel of cosmic bodies flying into it. Only around some holes does a bright glow form. After all, the rotation speed is very high, particles of celestial bodies heat up to millions of degrees and glow brightly

Cosmic black hole attracts all objects, twisting them in a spiral. As objects approach a black hole, they begin to accelerate and stretch out, like giant spaghetti. The force of attraction gradually increases and at some point becomes so monstrous that nothing can overcome it. This boundary is called the event horizon. Any event that happens behind it will remain invisible forever.

Scientists suggest that black holes can create tunnels in space - “wormholes”. If you fall into it, you will be able to pass through space and find yourself in another Universe, where the opposite white hole exists. Maybe someday this secret will be revealed and people will travel to other dimensions on powerful spaceships.

> Black holes

What's happened black hole– explanation for children: description with photos, how to find the Universe in space, how stars appear, the death, supermassive black holes of galaxies.

For the little ones parents or at school should explain that perceiving a black hole as an empty space is a grave mistake. On the contrary, an incredible amount of matter is concentrated in it, which is confined in a small space. To explanation for children was more colorful, just imagine if you took a star 10 times more massive than the Sun and tried to squeeze it into an area the size of New York City. Due to this pressure, the gravitational field becomes so strong that no one, not even a light beam, can escape. With the development of technology, NASA is able to learn more and more about these mysterious objects.

Begin explanation for children This is possible because the term “black hole” did not exist until 1967 (introduced by John Wheeler). But before this, for several centuries it was mentioned about the existence of strange objects that, due to their density and massiveness, do not release light. They were even predicted by Albert Einstein in general theory relativity. She proved that when a massive star dies, a small dense core remains. If a star is three times the mass of the sun, then gravity overcomes other forces, and we get a black hole.

Of course it's important explain to the children that researchers are unable to observe these features directly (telescopes only detect light, X-rays and other forms of electromagnetic radiation), so there is no need to wait for a photo of the black hole. But it is possible to calculate their location and even determine their size due to the influence they have on surrounding objects. For example, if it passes through a cloud of interstellar matter, then in the process it will begin to draw matter inward - accretion. The same thing will happen if a star passes nearby. True, a star can explode.

At the moment of attraction, the substance heats up and accelerates, releasing x-rays into space. Recent discoveries have spotted several powerful bursts of gamma rays, demonstrating the hole's devouring of nearby stars. At this moment, they stimulate the growth of some and stop others.

The death of a star is the beginning of a black hole

Most black holes arise from the leftover material of dying large stars (supernova explosions). Smaller stars become dense neutron stars, which lack the massiveness to trap light. If the mass of a star is 3 times greater than that of the Sun, then it becomes a candidate for a black hole. Important explain to the children one oddity. When a star collapses, its surface approaches an imaginary surface (event horizon). Time on the star itself becomes slower than that of the observer. When the surface reaches the event horizon, time freezes and the star can no longer collapse - a frozen, collapsing object.

Larger black holes can appear after a stellar collision. After its launch in December 2004, the NASA telescope was able to detect strong, fleeting flashes of light - gamma rays. Chandra and Hubble then collected data on the event and realized that these flares could be the result of a collision between a black hole and a neutron star, which creates a new black hole.

Although in the process of education children And parents We've already figured it out, but one thing remains a mystery. The holes seem to exist on two different scales. There are many black holes - the remains of massive stars. Typically, they are 10-24 times more massive than the Sun. Scientists constantly see them if an alien star comes critically close. But most black holes exist in isolation and simply cannot be seen. However, judging by the number of stars large enough to be black hole candidates, there must be tens of millions of billions of such black holes in the Milky Way.

There are also supermassive black holes, which are a million or even a billion times larger than our Sun. It is believed that such monsters live in the centers of almost all large galaxies (including ours).

For the little ones it will be interesting to know that for a long time Scientists believed that there was no average size for black holes. But data from Chandra, XMM-Newton and Hubble show that they are there.

It is possible that supermassive black holes arise from a chain reaction caused by the collision of stars in compact clusters. Because of this, a lot of massive stars accumulate, which collapse and produce black holes. These clusters then occupy the galactic center, where the black holes merge and become a supermassive member.

You might already understand that you won't be able to admire the black hole in high quality online because these objects do not release light. But children will be interested in studying photographs and diagrams created based on the contact of black holes and ordinary matter.

Space objects

Due to the relatively recent growth of interest in creating popular science films on the topic of space exploration, modern viewers have heard a lot about phenomena such as the singularity, or a black hole. However, movies obviously do not reveal the full nature of these phenomena, and sometimes even distort the constructed scientific theories for greater effectiveness. For this reason, the representation 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 Royal Society some hypothetical massive body that has such a strong gravitational attraction that the second cosmic velocity for it will exceed the speed of light. Escape velocity is the speed that a relatively small object would need to overcome its gravitational pull. celestial body and go beyond the closed orbit around this body. According to his calculations, a body with the density of the Sun and a radius of 500 solar radii will have a second cosmic velocity on its surface 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 will remain invisible to the observer - a kind of black spot against the background of dark space.

However, Michell's concept of a supermassive body did not attract much interest until the work of Einstein. Let us recall that the latter defined the speed of light as the maximum speed of information transfer. In addition, Einstein expanded the theory of gravity to speeds close to the speed of light (). As a result, it was no longer relevant to apply 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 identified, of which there are only three: mass, electric charge and angular momentum. It should be noted the significant contribution of the Indian astrophysicist Subramanian Chandrasekhar, who created a fundamental monograph: “ Mathematical theory black holes."

Thus, the solution to Einstein’s equations is presented in four options for four possible types of black holes:

BH without rotation and without charge – Schwarzschild solution. One of the first descriptions of a black hole (1916) using Einstein’s equations, but without taking into account two of the three parameters of the body. The solution of the German physicist Karl Schwarzschild allows one to calculate the external gravitational field of a spherical massive body. The peculiarity of the concept of black holes of the German scientist is the presence of an event horizon and hiding behind it. Schwarzschild was also the first to calculate the gravitational radius, which received his name, which determines the radius of the sphere on which the event horizon for a body with a given mass would be located.
BH without rotation with charge – 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.
BH with rotation and without charge - Kerr's solution (1963). A rotating Kerr black hole differs from a static one by the presence of a so-called ergosphere (read more about this and other components of a black hole).
BH with rotation and charge - Kerr-Newman solution. This decision was calculated in 1965 and at at the moment is the most complete, since it takes into account all three parameters of the black hole. However, it is still assumed that in nature black holes have an insignificant charge.

Black hole formation

There are several theories about how a black hole forms and appears, the most famous of which is that it arises as a result of the gravitational collapse of a star with sufficient mass. Such compression can end the evolution of stars with a mass of more than three solar masses. Upon completion of the thermo nuclear reactions inside such stars they begin to rapidly compress into super-dense. If the gas pressure of a neutron star cannot compensate for gravitational forces, that is, the mass of the star overcomes the so-called. Oppenheimer-Volkoff limit, then the collapse continues, resulting in matter being 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 at the stage of transformation into a galaxy or some kind of cluster. If there is insufficient internal pressure to compensate for the same gravitational forces, a black hole may arise.

Two other scenarios remain hypothetical:

The occurrence of a black hole as a result of the so-called primordial black holes.
Occurrence as a result of nuclear reactions occurring at high energies. An example of such reactions is experiments at 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 the 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 existing physical theories do not work inside it. Thus, the physics of the singularity remains a mystery to scientists today. a black hole is a certain boundary, crossing which a physical object loses the opportunity to return back beyond its limits and will definitely “fall” into the singularity of the black hole.

The structure of a black hole becomes somewhat more complicated in the case of the Kerr solution, namely in the presence of rotation of the black hole. Kerr's solution assumes that the hole has an ergosphere. The ergosphere is a certain region 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 some kind of analogue of an accretion disk, representing rotating matter around massive bodies. If a static Schwarzschild black hole is represented as a black sphere, then the Kerry black hole, due to the presence of an ergosphere, has the shape of an oblate ellipsoid, in the form of which we often saw black holes in drawings, in old movies or video games.

How much does a black hole weigh? – The largest theoretical material on the emergence 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 mass of a black hole is 2.5 - 3 solar masses. The heaviest black hole that has been discovered (in the galaxy NGC 4889) has a mass of 21 billion solar masses. However, we should not forget about black holes that hypothetically arise as a result of 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 magnitude, namely 2·10−5 g.
Black hole size. The minimum radius of a black hole 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 located, is about 2.95 km, then the minimum radius of a black hole of 3 solar masses will be about nine kilometers. Such relatively small sizes are hard to comprehend when we're talking about about massive objects that attract everything around them. 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 detected black holes have masses greater than 10 5 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 that of air. Based on these calculations, it is logical to assume that the formation of a black hole occurs not due to compression of matter, but as a result of the accumulation large quantity matter to some extent. In the case of quantum black holes, their density can be about 10 94 kg/m³.
The temperature of a black hole also depends inversely on its mass. This temperature directly related to . The spectrum of this radiation coincides with the spectrum of an absolutely black body, that is, a body that absorbs all incident radiation. The radiation spectrum of an absolutely black body depends only on its temperature, then the temperature of the black hole can be determined from the Hawking radiation spectrum. As mentioned above, this radiation is 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 black holes is so low that it does not allow this radiation to be detected. 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 minutes), such black holes can emit energy of the order of ten million atomic bombs. But, fortunately, to create such hypothetical objects would require energy 10 14 times more than that, which was achieved today at the Large Hadron Collider. In addition, such phenomena have never been observed by astronomers.

What does a black hole consist of?

Another question worries both scientists and those who are simply interested in astrophysics - what does a black hole consist of? There is no clear answer to this question, since it is not possible to look beyond the event horizon surrounding any black hole. In addition, as mentioned earlier, 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 that now revolve around it - various kinds of cosmic bodies and cosmic gas. The event horizon is just a thin implicit boundary, 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. A similar reaction actually occurs in nature, and with the formation of a neutron, neutrino radiation occurs. However, these are just assumptions.

What happens if you fall into a black hole?

Falling into an astrophysical black hole causes the body to stretch. Consider a hypothetical suicide cosmonaut who heads into a black hole wearing only a spacesuit, 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) at which 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 subject to a noticeably greater gravitational influence than, for example, the head. Then, due to gravity, or rather tidal forces, the legs will “fall” faster. Thus, the body begins to gradually elongate in length. To describe this phenomenon, astrophysicists have come up with a rather creative term - spaghettification. Further stretching of the body will probably decompose it into atoms, which, sooner or later, will reach a singularity. One can only guess how a person will feel in this situation. It is worth noting that the effect of stretching a body is inversely proportional to the mass of the black hole. That is, if a black hole with the mass of three Suns instantly stretches/tears the body, then the supermassive black hole will have lower tidal forces and, there are assumptions that some physical materials could “tolerate” such deformation without losing their structure.

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

It is noteworthy that for an observer from the outside, all bodies that fly up to the event horizon will remain at the edge of this horizon until their image disappears. The reason for this phenomenon is gravitational redshift. Simplifying somewhat, we can say that the light falling on the body of a suicide cosmonaut “frozen” at the event horizon will change its frequency due to its slowed down time. Because time goes by slower, 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 low frequency - red. A shift of light along the spectrum will take place, as the suicide cosmonaut moves further and further away from the observer, although 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 detected only in the region of infrared radiation, later in radio frequency, and as a result the radiation will be completely elusive.

Despite the above, it is assumed that in very large supermassive black holes, tidal forces do not change so much with distance and act almost uniformly on the falling body. In this case, falling spacecraft would retain its structure. A reasonable question arises: where does the black hole lead? This question can be answered by the work of some scientists, linking two phenomena such as wormholes and black holes.

Back in 1935, Albert Einstein and Nathan Rosen put forward a hypothesis about the existence of so-called wormholes, connecting two points of space-time through places of significant curvature of the latter - an Einstein-Rosen bridge or wormhole. For such a powerful curvature of space, bodies with gigantic mass would be required, the role of which would be perfectly fulfilled by black holes.

The Einstein-Rosen Bridge is considered an impassable wormhole because it is small in size and unstable.

A traversable wormhole is possible within the framework of the theory of black and white holes. Where the white hole is the output of information trapped in the black hole. The white hole is described within the framework of general relativity, but today 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, both in the case of the Morris-Thorne wormhole and 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, you should take into account the size 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.
Black holes average weight . Conditional intermediate type black holes that have grown in size by consuming nearby objects, such as gas accumulations, a nearby star (in two-star systems), and other cosmic bodies.
Supermassive black hole. Compact objects with 10 5 -10 10 solar masses. Distinctive properties Such BHs are characterized by a paradoxically low density, as well as weak tidal forces, which were mentioned earlier. This is exactly the supermassive black hole at the center of our Milky Way galaxy (Sagittarius A*, Sgr A*), as well as most other galaxies.

Candidates for the ChD

The nearest black hole, or rather a candidate for the role of a black hole, is an object (V616 Monoceros), 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 mass of the Sun, as well as an invisible small body whose mass is 3–5 solar masses. If this object turns out to be a small black hole of stellar mass, then it will rightfully become the nearest black hole.

Following this object, the second closest black hole is the object Cygnus 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 have increased this distance by at least 15 times.

How many black holes are there in our galaxy?

There is no exact answer to this question, since it is quite difficult to observe them, and over the entire period of studying the sky, scientists managed to discover about a dozen black holes within Milky Way. Without indulging in calculations, we note that there are about 100–400 billion stars in our galaxy, and approximately 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 detect black holes of enormous size, it is logical to assume that most likely the majority of black holes 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) revolving around 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 enormous mass (100,000 solar masses), scientists assume 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 largest black hole

The largest black hole in the Universe that scientists have discovered is a supermassive black hole, FSRQ blazar, in the center of the galaxy S5 0014+81, at a distance of 1.2 10 10 light years from Earth. According to preliminary observation results using the Swift space observatory, the mass of the black hole was 40 billion (40·10 9) solar masses, and the Schwarzschild radius of such a hole was 118.35 billion kilometers (0.013 light years). In addition, according to calculations, it arose 12.1 billion years ago (1.6 billion years after the Big Bang). If this giant black hole does not absorb the matter surrounding it, it will live to the era of black holes - one of the eras of 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, it will become one of the last black holes that will exist in the Universe.

The other two known black holes, although they do not have their own names, have highest value for the study of black holes, since they confirmed their existence experimentally, and also provided important results for the study of gravity. We are talking about the event GW150914, which is the collision of two black holes into one. This event made it possible to register.

Detection of black holes

Before considering methods for detecting black holes, we should answer the question - why is a black hole black? – the answer to this does not require deep knowledge of astrophysics and cosmology. The fact is that a black hole absorbs all the radiation falling on it and does not emit at all, if you do not take into account the hypothetical one. If we consider this phenomenon in more detail, we can assume that processes leading to the release of energy in the form of electromagnetic radiation do not occur inside black holes. Then, if a black hole emits, it does so 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 that the temperature of black holes is completely low.

Another generally accepted theory says that electromagnetic radiation is not at all capable of leaving the event horizon. It is most likely that photons (particles of light) are not attracted by massive objects, since, according to the theory, they themselves have no mass. However, the black hole still “attracts” photons of light through the distortion of space-time. If we imagine a black hole in space as a kind of depression on the smooth surface of space-time, then there is a certain distance from the center of the black hole, approaching which light will no longer be able to move away from it. That is, roughly speaking, the light begins to “fall” into a “hole” that 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 into the region of low-frequency long-wave radiation until it loses energy altogether.

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

Detection methods

Let's look at 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 certain clusters of cosmic bodies and gas, which are among the brightest astronomical objects in the Universe. Since they have a high luminescence intensity at relatively small sizes, there is reason to assume that the center of these objects is a supermassive black hole, attracting surrounding matter. Due to such a powerful gravitational attraction, the attracted matter is so heated that it radiates intensely. The discovery of such objects is usually compared with the discovery of a black hole. Sometimes quasars can emit jets of heated plasma in two directions - relativistic jets. The reasons for the appearance of such jets are not entirely clear, but they are probably caused by the interaction of the magnetic fields of the black hole and the accretion disk, and are not emitted by the direct black hole.

Jet in the M87 galaxy shooting from the center of the black hole

To summarize the above, you can imagine, close up: this is a spherical black object around which highly heated matter rotates, forming a luminous accretion disk.

Mergers and collisions of black holes

One of 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 most striking example is the previously mentioned event called GW150914, when two black holes came so close that, as a result of their mutual gravitational attraction, they merged into one. An important consequence of this collision was the emergence of gravitational waves.

According to the definition, gravitational waves are changes in the gravitational field that propagate in a wave-like manner from massive moving objects. When two such objects come closer, they begin to rotate around a common center of gravity. As they get closer, their rotation around their own axis increases. Such alternating oscillations of the gravitational field at some moment can form one powerful gravitational wave, which can spread through space for millions of light years. Thus, at a distance of 1.3 billion light years, two black holes collided, generating 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 its definition, nothing can leave the black hole if it has crossed its event horizon. It is known that the possibility of emission of particles from a black hole was first mentioned by the Soviet theoretical physicist Vladimir Gribov, 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 the tunneling effect. Later, using quantum mechanics, the English theoretical physicist Stephen Hawking built his own, slightly different theory. You can read more about this phenomenon. Briefly speaking, in a vacuum there are so-called virtual particles, which are constantly born in pairs and annihilate each other, without interacting with the outside world. But if such pairs appear on the event horizon of a black hole, then strong gravity is hypothetically capable of separating them, with one particle falling into the black hole and the other moving away from the black hole. And since a particle flying away from a hole can be observed, and therefore has positive energy, then a particle falling into a hole must have negative energy. Thus, the black hole will lose its energy and an effect will occur, which is called black hole evaporation.

According to existing models of a black hole, as mentioned earlier, as its mass decreases, its radiation becomes more intense. Then, at the final stage of the black hole's existence, when it may shrink to the size of a quantum black hole, it will release a huge amount of energy in the form of radiation, which could 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 with a mass of about 10 12 kg would have evaporated and exploded around our time. Be that as it may, such explosions have never been noticed by astronomers.

Despite Hawking's proposed mechanism for destroying black holes, the properties of Hawking's radiation cause a paradox within the framework of quantum mechanics. If a black hole absorbs a certain 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 absorbing 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 black hole. A definitive solution to this paradox has never been found. Known solutions to the paradox:

The invalidity of Hawking's theory. This entails the impossibility of destroying a black hole and its constant growth.
Presence of white holes. In this case, the absorbed information does not disappear, but is simply thrown out into another Universe.
The 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 unknown to scientists.

In 1970, an English scientist formulated the so-called. “the principle of cosmic censorship” - “Nature abhors naked singularity.” This means that singularities form only in hidden places, 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 arise.
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 have not been studied.
It is not known for certain what happens at the final stage of the existence of a black hole, and what remains after its quantum decay.

Interesting facts about black holes

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

BHs 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 the black hole 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 does not occur due to compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume.
Time passes much slower for bodies absorbed by a black hole than for an external observer. In addition, the absorbed bodies stretch significantly inside the black hole, which scientists call spaghettification.
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 theoretical model, The Universe will reach the so-called era of black holes, when BHs will become the dominant bodies in the Universe.