Black holes are perhaps the most mysterious and enigmatic astronomical objects in our Universe; from the moment of their discovery, they have attracted the attention of scientists and excite the imagination of science fiction writers. What are black holes and what do they represent? Black holes are extinct stars that, due to their physical characteristics, have such a high density and such powerful gravity that even light cannot escape beyond them.
History of the discovery of black holes
For the first time, the theoretical existence of black holes, long before their actual discovery, was suggested by a certain D. Michel (an English priest from Yorkshire, who is interested in astronomy in his spare time) back in 1783. According to his calculations, if we take ours and compress it (in modern computer language, archive it) to a radius of 3 km, such a large (simply enormous) gravitational force will be formed that even light will not be able to leave it. This is how the concept of a “black hole” appeared, although in fact it is not black at all; in our opinion, the term “dark hole” would be more appropriate, because it is precisely the absence of light that occurs.
Later, in 1918, the great scientist Albert Einstein wrote about the issue of black holes in the context of the theory of relativity. But it was only in 1967, through the efforts of the American astrophysicist John Wheeler, that the concept of black holes finally won a place in academic circles.
Be that as it may, D. Michel, Albert Einstein, and John Wheeler in their works assumed only the theoretical existence of these mysterious celestial objects in outer space, but the real discovery of black holes took place in 1971, it was then that they were first noticed in telescope.
This is what a black hole looks like.
How black holes form in space
As we know from astrophysics, all stars (including our Sun) have some limited supply of fuel. And although the life of a star can last billions of light years, sooner or later this conditional supply of fuel comes to an end, and the star “goes out”. The process of “fading” of a star is accompanied by intense reactions, during which the star undergoes a significant transformation and, depending on its size, can turn into a white dwarf, a neutron star or a black hole. Moreover, the largest stars, with incredibly impressive sizes, usually turn into a black hole - due to the compression of these most incredible sizes, there is a multiple increase in the mass and gravitational force of the newly formed black hole, which turns into a kind of galactic vacuum cleaner - absorbing everything and everyone around it.
A black hole swallows a star.
A small note - our Sun, by galactic standards, is not at all a large star and after its extinction, which will occur in about a few billion years, it will most likely not turn into a black hole.
But let's be honest with you - today, scientists do not yet know all the intricacies of the formation of a black hole; undoubtedly, this is an extremely complex astrophysical process, which in itself can last millions of light years. Although it is possible to advance in this direction could be the discovery and subsequent study of the so-called intermediate black holes, that is, stars in a state of extinction, in which the active process of black hole formation is taking place. By the way, a similar star was discovered by astronomers in 2014 in the arm of a spiral galaxy.
How many black holes are there in the Universe?
According to the theories of modern scientists, there may be up to hundreds of millions of black holes in our Milky Way galaxy. There may be no less of them in our neighboring galaxy, to which there is nothing to fly from our Milky Way - 2.5 million light years.
Black hole theory
Despite the enormous mass (which is hundreds of thousands of times greater than the mass of our Sun) and the incredible strength of gravity, it was not easy to see black holes through a telescope, because they do not emit light at all. Scientists managed to notice the black hole only at the moment of its “meal” - absorption of another star, at this moment characteristic radiation appears, which can already be observed. Thus, the black hole theory has found actual confirmation.
Properties of black holes
The main property of a black hole is its incredible gravitational fields, which do not allow the surrounding space and time to remain in their usual state. Yes, you heard right, time inside a black hole passes many times slower than usual, and if you were there, then when you returned back (if you were so lucky, of course), you would be surprised to notice that centuries have passed on Earth, and you haven’t even grown old made it in time. Although let’s be truthful, if you were inside a black hole, you would hardly survive, since the force of gravity there is such that any material object would simply be torn apart, not even into pieces, into atoms.
But if you were even close to a black hole, within the influence of its gravitational field, you would also have a hard time, since the more you resist its gravity, trying to fly away, the faster you would fall into it. The reason for this seemingly paradox is the gravitational vortex field that all black holes possess.
What if a person falls into a black hole
Evaporation of black holes
English astronomer S. Hawking discovered an interesting fact: black holes also appear to emit evaporation. True, this only applies to holes of relatively small mass. The powerful gravity around them gives birth to pairs of particles and antiparticles, one of the pair is pulled in by the hole, and the second is expelled out. Thus, the black hole emits hard antiparticles and gamma-rays. This evaporation or radiation from a black hole was named after the scientist who discovered it - “Hawking radiation”.
The largest black hole
According to the black hole theory, at the center of almost all galaxies there are huge black holes with masses from several million to several billion solar masses. And relatively recently, scientists discovered the two largest black holes known to date; they are located in two nearby galaxies: NGC 3842 and NGC 4849.
NGC 3842 is the brightest galaxy in the constellation Leo, located 320 million light years away from us. At its center there is a huge black hole weighing 9.7 billion solar masses.
NGC 4849, a galaxy in the Coma cluster, 335 million light-years away, boasts an equally impressive black hole.
The gravitational field of these giant black holes, or in academic terms, their event horizon, is approximately 5 times the distance from the Sun to ! Such a black hole would eat our solar system and not even choke.
The smallest black hole
But in the vast family of black holes there are also very small representatives. Thus, the most dwarf black hole discovered by scientists at the moment is only 3 times the mass of our Sun. In fact, this is the theoretical minimum required for the formation of a black hole; if that star were slightly smaller, the hole would not have formed.
Black holes are cannibals
Yes, there is such a phenomenon, as we wrote above, black holes are a kind of “galactic vacuum cleaners” that absorb everything around them, including... other black holes. Recently, astronomers discovered that a black hole from one galaxy was being eaten by an even larger black glutton from another galaxy.
- According to the hypotheses of some scientists, black holes are not only galactic vacuum cleaners that suck everything into themselves, but under certain circumstances they can themselves give birth to new universes.
- Black holes can evaporate over time. We wrote above that the English scientist Stephen Hawking discovered that black holes have the property of radiation and after some very long period of time, when there is nothing left to absorb around, the black hole will begin to evaporate more, until over time it gives up all its mass into surrounding space. Although this is only an assumption, a hypothesis.
- Black holes slow down time and bend space. We have already written about time dilation, but space under the conditions of a black hole will also be completely curved.
- Black holes limit the number of stars in the Universe. Namely, their gravitational fields prevent the cooling of gas clouds in space, from which, as is known, new stars are born.
Black holes on the Discovery Channel, video
And in conclusion, we offer you an interesting scientific documentary about black holes from the Discovery Channel
Mysterious and elusive black holes. The laws of physics confirm the possibility of their existence in the universe, but many questions still remain. Numerous observations show that holes exist in the universe and there are more than a million of these objects.
What are black holes?
Back in 1915, when solving Einstein’s equations, the phenomenon of “black holes” was predicted. However, the scientific community became interested in them only in 1967. They were then called “collapsed stars”, “frozen stars”.
Nowadays, a black hole is a region of time and space that has such gravity that even a ray of light cannot escape from it.
How are black holes formed?
There are several theories for the appearance of black holes, which are divided into hypothetical and realistic. The simplest and most widespread realistic one is the theory of gravitational collapse of large stars.
When a sufficiently massive star, before “death,” grows in size and becomes unstable, using up its last fuel. At the same time, the mass of the star remains unchanged, but its size decreases as the so-called densification occurs. In other words, when compacted, the heavy core “falls” into itself. In parallel with this, compaction leads to a sharp increase in the temperature inside the star and the outer layers of the celestial body break away, from which new stars are formed. At the same time, in the center of the star, the core falls into its own “center.” As a result of the action of gravitational forces, the center collapses to a point - that is, the gravitational forces are so strong that they absorb the compacted core. This is how a black hole is born, which begins to distort space and time so that even light cannot escape from it.
At the center of all galaxies is a supermassive black hole. According to Einstein's theory of relativity:
“Any mass distorts space and time.”
Now imagine how much a black hole distorts time and space, because its mass is enormous and at the same time squeezed into an ultra-small volume. This ability causes the following oddity:
“Black holes have the ability to practically stop time and compress space. Because of this extreme distortion, the holes become invisible to us.”
If black holes are not visible, how do we know they exist?
Yes, even though a black hole is invisible, it should be noticeable due to the matter that falls into it. As well as stellar gas, which is attracted by a black hole; when approaching the event horizon, the temperature of the gas begins to rise to ultra-high values, which leads to a glow. This is why black holes glow. Thanks to this, albeit weak, glow, astronomers and astrophysicists explain the presence in the center of the galaxy of an object with a small volume but a huge mass. Currently, as a result of observations, about 1000 objects have been discovered that are similar in behavior to black holes.
Black holes and galaxies
How can black holes affect galaxies? This question plagues scientists all over the world. There is a hypothesis according to which it is the black holes located in the center of the galaxy that influence its shape and evolution. And that when two galaxies collide, black holes merge and during this process such a huge amount of energy and matter is released that new stars are formed.
Types of black holes
- According to existing theory, there are three types of black holes: stellar, supermassive, and miniature. And each of them was formed in a special way.
- - Black holes of stellar masses, it grows to enormous sizes and collapses.
- Supermassive black holes, which can have a mass equivalent to millions of Suns, are likely to exist at the centers of almost all galaxies, including our Milky Way. Scientists still have different hypotheses for the formation of supermassive black holes. So far, only one thing is known - supermassive black holes are a by-product of the formation of galaxies. Supermassive black holes - they differ from ordinary ones in that they have a very large size, but paradoxically low density. - - No one has yet been able to detect a miniature black hole that would have a mass less than the Sun. It is possible that miniature holes could have formed shortly after the “Big Bang”, which is the exact beginning of the existence of our universe (about 13.7 billion years ago).
- - Quite recently, a new concept was introduced as “white black holes”. This is still a hypothetical black hole, which is the opposite of a black hole. Stephen Hawking actively studied the possibility of the existence of white holes.
- - Quantum black holes - they exist only in theory so far. Quantum black holes can be formed when ultra-small particles collide as a result of a nuclear reaction.
- - Primary black holes are also a theory. They were formed immediately after their origin.
At the moment, there are a large number of open questions that have yet to be answered by future generations. For example, can so-called “wormholes” really exist, with the help of which one can travel through space and time. What exactly happens inside a black hole and what laws these phenomena obey. And what about the disappearance of information in a black hole?
S. TRANKOVSKY
Among the most important and interesting problems of modern physics and astrophysics, Academician V.L. Ginzburg named issues related to black holes (see “Science and Life” No. 11, 12, 1999). The existence of these strange objects was predicted more than two hundred years ago, the conditions leading to their formation were precisely calculated in the late 30s of the 20th century, and astrophysics began to seriously study them less than forty years ago. Today, scientific journals around the world annually publish thousands of articles on black holes.
The formation of a black hole can occur in three ways.
This is how it is customary to depict processes occurring in the vicinity of a collapsing black hole. Over time (Y), the space (X) around it (the shaded area) shrinks, rushing towards the singularity.
The gravitational field of a black hole introduces severe distortions into the geometry of space.
A black hole, invisible through a telescope, reveals itself only by its gravitational influence.
In the powerful gravitational field of a black hole, particle-antiparticle pairs are born.
The birth of a particle-antiparticle pair in the laboratory.
HOW THEY ARISE
A luminous celestial body, having a density equal to that of the Earth, and a diameter two hundred and fifty times greater than the diameter of the Sun, due to the force of its gravity, will not allow its light to reach us. Thus, it is possible that the largest luminous bodies in the Universe remain invisible precisely because of their size.
Pierre Simon Laplace.
Exposition of the world system. 1796
In 1783, the English mathematician John Mitchell, and thirteen years later, independently of him, the French astronomer and mathematician Pierre Simon Laplace, conducted a very strange study. They looked at the conditions under which light would be unable to escape the star.
The logic of the scientists was simple. For any astronomical object (planet or star), it is possible to calculate the so-called escape velocity, or the second cosmic velocity, which allows any body or particle to leave it forever. And in the physics of that time, Newton’s theory reigned supreme, according to which light is a flow of particles (the theory of electromagnetic waves and quanta was still almost a hundred and fifty years away). The escape velocity of particles can be calculated based on the equality of the potential energy on the surface of the planet and the kinetic energy of a body that has “escaped” to an infinitely large distance. This speed is determined by the formula #1#
Where M- mass of the space object, R- its radius, G- gravitational constant.
From this we can easily obtain the radius of a body of a given mass (later called the “gravitational radius” r g "), at which the escape velocity is equal to the speed of light:
This means that a star compressed into a sphere with a radius r g< 2GM/c 2 will stop emitting - the light will not be able to leave it. A black hole will appear in the Universe.
It is easy to calculate that the Sun (its mass is 2.1033 g) will turn into a black hole if it contracts to a radius of approximately 3 kilometers. The density of its substance will reach 10 16 g/cm 3 . The radius of the Earth, compressed into a black hole, would decrease to about one centimeter.
It seemed incredible that there could be forces in nature capable of compressing a star to such an insignificant size. Therefore, the conclusions from the works of Mitchell and Laplace were considered for more than a hundred years to be something of a mathematical paradox that had no physical meaning.
Rigorous mathematical proof that such an exotic object in space was possible was obtained only in 1916. German astronomer Karl Schwarzschild, after analyzing the equations of Albert Einstein's general theory of relativity, obtained an interesting result. Having studied the motion of a particle in the gravitational field of a massive body, he came to the conclusion: the equation loses its physical meaning (its solution turns to infinity) when r= 0 and r = r g.
The points at which the characteristics of the field become meaningless are called singular, that is, special. The singularity at the zero point reflects the pointwise, or, what is the same thing, the centrally symmetric structure of the field (after all, any spherical body - a star or a planet - can be represented as a material point). And points located on a spherical surface with a radius r g, form the very surface from which the escape velocity is equal to the speed of light. In the general theory of relativity it is called the Schwarzschild singular sphere or the event horizon (why will become clear later).
Already based on the example of objects familiar to us - the Earth and the Sun - it is clear that black holes are very strange objects. Even astronomers who deal with matter at extreme values of temperature, density and pressure consider them very exotic, and until recently not everyone believed in their existence. However, the first indications of the possibility of the formation of black holes were already contained in A. Einstein’s general theory of relativity, created in 1915. The English astronomer Arthur Eddington, one of the first interpreters and popularizers of the theory of relativity, in the 30s derived a system of equations describing the internal structure of stars. It follows from them that the star is in equilibrium under the influence of oppositely directed gravitational forces and internal pressure created by the movement of hot plasma particles inside the star and the pressure of radiation generated in its depths. This means that the star is a gas ball, in the center of which there is a high temperature, gradually decreasing towards the periphery. From the equations, in particular, it followed that the surface temperature of the Sun was about 5500 degrees (which was quite consistent with the data of astronomical measurements), and in its center it should be about 10 million degrees. This allowed Eddington to make a prophetic conclusion: at this temperature, a thermonuclear reaction “ignites”, sufficient to ensure the glow of the Sun. Atomic physicists of that time did not agree with this. It seemed to them that it was too “cold” in the depths of the star: the temperature there was not enough for the reaction to “go.” To this the enraged theorist replied: “Look for a hotter place!”
And in the end, he turned out to be right: a thermonuclear reaction really occurs in the center of the star (another thing is that the so-called “standard solar model”, based on ideas about thermonuclear fusion, apparently turned out to be incorrect - see, for example, “Science and life" No. 2, 3, 2000). But nevertheless, the reaction in the center of the star takes place, the star shines, and the radiation that arises keeps it in a stable state. But the nuclear “fuel” in the star burns out. The release of energy stops, the radiation goes out, and the force restraining gravitational attraction disappears. There is a limit on the mass of a star, after which the star begins to shrink irreversibly. Calculations show that this happens if the mass of the star exceeds two to three solar masses.
GRAVITATIONAL COLLAPSE
At first, the rate of contraction of the star is small, but its rate continuously increases, since the force of gravity is inversely proportional to the square of the distance. The compression becomes irreversible; there are no forces capable of counteracting self-gravity. This process is called gravitational collapse. The speed of movement of the star's shell towards its center increases, approaching the speed of light. And here the effects of the theory of relativity begin to play a role.
The escape velocity was calculated based on Newtonian ideas about the nature of light. From the point of view of general relativity, phenomena in the vicinity of a collapsing star occur somewhat differently. In its powerful gravitational field, a so-called gravitational redshift occurs. This means that the frequency of radiation coming from a massive object is shifted towards lower frequencies. In the limit, at the boundary of the Schwarzschild sphere, the radiation frequency becomes zero. That is, an observer located outside of it will not be able to find out anything about what is happening inside. That is why the Schwarzschild sphere is called the event horizon.
But decreasing the frequency equals slowing down time, and when the frequency becomes zero, time stops. This means that an outside observer will see a very strange picture: the shell of a star, falling with increasing acceleration, stops instead of reaching the speed of light. From his point of view, the compression will stop as soon as the size of the star approaches gravitational
usu. He will never see even one particle “dive” under the Schwarzschiel sphere. But for a hypothetical observer falling into a black hole, everything will be over in a matter of moments on his watch. Thus, the gravitational collapse time of a star the size of the Sun will be 29 minutes, and a much denser and more compact neutron star will take only 1/20,000 of a second. And here he faces trouble associated with the geometry of space-time near a black hole.
The observer finds himself in a curved space. Near the gravitational radius, gravitational forces become infinitely large; they stretch the rocket with the astronaut-observer into an infinitely thin thread of infinite length. But he himself will not notice this: all his deformations will correspond to the distortions of space-time coordinates. These considerations, of course, refer to an ideal, hypothetical case. Any real body will be torn apart by tidal forces long before approaching the Schwarzschild sphere.
DIMENSIONS OF BLACK HOLES
The size of a black hole, or more precisely, the radius of the Schwarzschild sphere, is proportional to the mass of the star. And since astrophysics does not impose any restrictions on the size of a star, a black hole can be arbitrarily large. If, for example, it arose during the collapse of a star with a mass of 10 8 solar masses (or due to the merger of hundreds of thousands, or even millions of relatively small stars), its radius will be about 300 million kilometers, twice the Earth’s orbit. And the average density of the substance of such a giant is close to the density of water.
Apparently, these are the kind of black holes that are found in the centers of galaxies. In any case, astronomers today count about fifty galaxies, in the centers of which, judging by indirect evidence (discussed below), there are black holes with a mass of about a billion (10 9) solar. Our Galaxy also apparently has its own black hole; Its mass was estimated quite accurately - 2.4. 10 6 ±10% of the mass of the Sun.
The theory suggests that along with such supergiants, black mini-holes with a mass of about 10 14 g and a radius of about 10 -12 cm (the size of an atomic nucleus) should also arise. They could appear in the first moments of the existence of the Universe as a manifestation of very strong inhomogeneity of space-time with colossal energy density. Today, researchers realize the conditions that existed in the Universe at that time at powerful colliders (accelerators using colliding beams). Experiments at CERN earlier this year produced quark-gluon plasma - matter that existed before the emergence of elementary particles. Research into this state of matter continues at Brookhaven, the American accelerator center. It is capable of accelerating particles to energies one and a half to two orders of magnitude higher than the accelerator in
CERN. The upcoming experiment has caused serious concern: will a mini-black hole arise during its implementation, which will bend our space and destroy the Earth?
This fear resonated so strongly that the US government was forced to convene an authoritative commission to examine this possibility. A commission consisting of prominent researchers concluded: the energy of the accelerator is too low for a black hole to arise (this experiment is described in the journal Science and Life, No. 3, 2000).
HOW TO SEE THE INVISIBLE
Black holes emit nothing, not even light. However, astronomers have learned to see them, or rather, to find “candidates” for this role. There are three ways to detect a black hole.
1. It is necessary to monitor the rotation of stars in clusters around a certain center of gravity. If it turns out that there is nothing in this center, and the stars seem to be spinning around an empty space, we can say quite confidently: in this “emptiness” there is a black hole. It was on this basis that the presence of a black hole in the center of our Galaxy was assumed and its mass was estimated.
2. A black hole actively sucks matter into itself from the surrounding space. Interstellar dust, gas, and matter from nearby stars fall onto it in a spiral, forming a so-called accretion disk, similar to the ring of Saturn. (This is precisely the scarecrow in the Brookhaven experiment: a mini-black hole that appeared in the accelerator will begin to suck the Earth into itself, and this process could not be stopped by any force.) Approaching the Schwarzschild sphere, the particles experience acceleration and begin to emit in the X-ray range. This radiation has a characteristic spectrum similar to the well-studied radiation of particles accelerated in a synchrotron. And if such radiation comes from some region of the Universe, we can say with confidence that there must be a black hole there.
3. When two black holes merge, gravitational radiation occurs. It is calculated that if the mass of each is about ten solar masses, then when they merge in a matter of hours, energy equivalent to 1% of their total mass will be released in the form of gravitational waves. This is a thousand times more than the light, heat and other energy that the Sun emitted during its entire existence - five billion years. They hope to detect gravitational radiation with the help of gravitational wave observatories LIGO and others, which are now being built in America and Europe with the participation of Russian researchers (see “Science and Life” No. 5, 2000).
And yet, although astronomers have no doubts about the existence of black holes, no one dares to categorically assert that exactly one of them is located at a given point in space. Scientific ethics and the integrity of the researcher require an unambiguous answer to the question posed, one that does not tolerate discrepancies. It is not enough to estimate the mass of an invisible object; you need to measure its radius and show that it does not exceed the Schwarzschild radius. And even within our Galaxy this problem is not yet solvable. That is why scientists show a certain restraint in reporting their discovery, and scientific journals are literally filled with reports of theoretical work and observations of effects that can shed light on their mystery.
However, black holes have one more property, theoretically predicted, which might make it possible to see them. But, however, under one condition: the mass of the black hole should be much less than the mass of the Sun.
A BLACK HOLE CAN ALSO BE “WHITE”
For a long time, black holes were considered the embodiment of darkness, objects that in a vacuum, in the absence of absorption of matter, emit nothing. However, in 1974, the famous English theorist Stephen Hawking showed that black holes can be assigned a temperature, and therefore should radiate.
According to the concepts of quantum mechanics, vacuum is not emptiness, but a kind of “foam of space-time,” a mishmash of virtual (unobservable in our world) particles. However, quantum energy fluctuations can “eject” a particle-antiparticle pair from the vacuum. For example, in the collision of two or three gamma quanta, an electron and a positron will appear as if out of nothing. This and similar phenomena have been repeatedly observed in laboratories.
It is quantum fluctuations that determine the radiation processes of black holes. If a pair of particles with energies E And -E(the total energy of the pair is zero) occurs in the vicinity of the Schwarzschild sphere, the further fate of the particles will be different. They can annihilate almost immediately or go under the event horizon together. In this case, the state of the black hole will not change. But if only one particle goes below the horizon, the observer will register another, and it will seem to him that it was generated by a black hole. At the same time, a black hole that absorbed a particle with energy -E, will reduce your energy, and with energy E- will increase.
Hawking calculated the speeds at which all these processes occur and came to the conclusion: the probability of absorption of particles with negative energy is higher. This means that the black hole loses energy and mass - it evaporates. In addition, it radiates as a completely black body with a temperature T = 6 . 10 -8 M With / M kelvins, where M c - mass of the Sun (2.10 33 g), M- the mass of the black hole. This simple relationship shows that the temperature of a black hole with a mass six times that of the sun is equal to one hundred millionth of a degree. It is clear that such a cold body emits practically nothing, and all the above reasoning remains valid. Mini-holes are another matter. It is easy to see that with a mass of 10 14 -10 30 grams, they are heated to tens of thousands of degrees and white-hot! It should be noted right away, however, that there are no contradictions with the properties of black holes: this radiation is emitted by a layer above the Schwarzschild sphere, and not below it.
So, the black hole, which seemed to be an eternally frozen object, sooner or later disappears, evaporating. Moreover, as she “loses weight,” the rate of evaporation increases, but it still takes an extremely long time. It is estimated that mini-holes weighing 10 14 grams, which appeared immediately after the Big Bang 10-15 billion years ago, should evaporate completely by our time. At the last stage of life, their temperature reaches colossal values, so the products of evaporation must be particles of extremely high energy. Perhaps they are the ones that generate widespread air showers in the Earth's atmosphere - EAS. In any case, the origin of particles of anomalously high energy is another important and interesting problem that can be closely related to no less exciting questions in the physics of black holes.
« Science fiction can be useful - it stimulates the imagination and relieves fear of the future. However, scientific facts can be much more surprising. Science fiction never even imagined the existence of such things as black holes»
Stephen Hawking
In the depths of the universe there are countless mysteries and secrets hidden for humans. One of them is black holes - objects that even the greatest minds of mankind cannot understand. Hundreds of astrophysicists are trying to uncover the nature of black holes, but at this stage we have not even proven their existence in practice.
Film directors dedicate their films to them, and among ordinary people black holes have become such a cult phenomenon that they are identified with the end of the world and inevitable death. They are feared and hated, but at the same time they are idolized and worshiped by the unknown that these strange fragments of the Universe conceal within themselves. Agree, being swallowed up by a black hole is such a romantic thing. With their help, it is possible, and they can also become guides for us in.
The yellow press often speculates on the popularity of black holes. Finding headlines in newspapers related to the end of the world due to another collision with a supermassive black hole is not a problem. Much worse is that the illiterate part of the population takes everything seriously and raises a real panic. To bring some clarity, we will take a journey to the origins of the discovery of black holes and try to understand what it is and how to approach it.
Invisible stars
It just so happens that modern physicists describe the structure of our Universe using the theory of relativity, which Einstein carefully provided to humanity at the beginning of the 20th century. Black holes become even more mysterious, at the event horizon of which all the laws of physics known to us, including Einstein’s theory, cease to apply. Isn't this wonderful? In addition, the conjecture about the existence of black holes was expressed long before Einstein himself was born.
In 1783 there was a significant increase in scientific activity in England. In those days, science went side by side with religion, they got along well together, and scientists were no longer considered heretics. Moreover, priests were engaged in scientific research. One of these servants of God was the English pastor John Michell, who wondered not only about questions of existence, but also completely scientific problems. Michell was a very titled scientist: initially he was a teacher of mathematics and ancient linguistics at one of the colleges, and after that he was accepted into the Royal Society of London for a number of discoveries.
John Michell studied seismology, but in his spare time he liked to think about the eternal and the cosmos. This is how he came up with the idea that somewhere in the depths of the Universe there could be supermassive bodies with such powerful gravity that in order to overcome the gravitational force of such a body it is necessary to move at a speed equal to or higher than the speed of light. If we accept such a theory as true, then even light will not be able to develop a second escape velocity (the speed necessary to overcome the gravitational attraction of the leaving body), so such a body will remain invisible to the naked eye.
Michell called his new theory “dark stars,” and at the same time tried to calculate the mass of such objects. He expressed his thoughts on this matter in an open letter to the Royal Society of London. Unfortunately, in those days such research was not of particular value to science, so Michell’s letter was sent to the archives. Only two hundred years later, in the second half of the 20th century, it was discovered among thousands of other records carefully stored in the ancient library.
The first scientific evidence for the existence of black holes
After Einstein's General Theory of Relativity was published, mathematicians and physicists seriously began solving the equations presented by the German scientist, which were supposed to tell us a lot of new things about the structure of the Universe. The German astronomer and physicist Karl Schwarzschild decided to do the same thing in 1916.
The scientist, using his calculations, came to the conclusion that the existence of black holes is possible. He was also the first to describe what was later called the romantic phrase "event horizon" - the imaginary boundary of space-time at a black hole, after crossing which there is a point of no return. Nothing will escape from the event horizon, not even light. It is beyond the event horizon that the so-called “singularity” occurs, where the laws of physics known to us cease to apply.
Continuing to develop his theory and solve equations, Schwarzschild discovered new secrets of black holes for himself and the world. Thus, he was able, solely on paper, to calculate the distance from the center of the black hole, where its mass is concentrated, to the event horizon. Schwarzschild called this distance the gravitational radius.
Despite the fact that mathematically, Schwarzschild's solutions were extremely correct and could not be refuted, the scientific community of the early 20th century could not immediately accept such a shocking discovery, and the existence of black holes was written off as a fantasy, which appeared every now and then in the theory of relativity. For the next decade and a half, space exploration for the presence of black holes was slow, and only a few adherents of the German physicist’s theory were engaged in it.
Stars giving birth to darkness
After Einstein's equations were sorted out, it was time to use the conclusions drawn to understand the structure of the Universe. In particular, in the theory of stellar evolution. It's no secret that in our world nothing lasts forever. Even stars have their own life cycle, albeit longer than a person.
One of the first scientists to become seriously interested in stellar evolution was the young astrophysicist Subramanyan Chandrasekhar, a native of India. In 1930, he published a scientific work that described the supposed internal structure of stars, as well as their life cycles.
Already at the beginning of the 20th century, scientists guessed about such a phenomenon as gravitational compression (gravitational collapse). At a certain point in its life, a star begins to contract at tremendous speed under the influence of gravitational forces. As a rule, this happens at the moment of the death of a star, but during gravitational collapse there are several ways for the continued existence of a hot ball.
Chandrasekhar's scientific adviser, Ralph Fowler, a respected theoretical physicist in his time, assumed that during gravitational collapse any star turns into a smaller and hotter one - a white dwarf. But it turned out that the student “broke” the teacher’s theory, which was shared by most physicists at the beginning of the last century. According to the work of a young Indian, the demise of a star depends on its initial mass. For example, only those stars whose mass does not exceed 1.44 times the mass of the Sun can become white dwarfs. This number was called the Chandrasekhar limit. If the mass of the star exceeded this limit, then it dies in a completely different way. Under certain conditions, such a star at the moment of death can be reborn into a new, neutron star - another mystery of the modern Universe. The theory of relativity tells us another option - compression of the star to ultra-small values, and this is where the fun begins.
In 1932, an article appeared in one of the scientific journals in which the brilliant physicist from the USSR Lev Landau suggested that during collapse a supermassive star is compressed into a point with an infinitesimal radius and infinite mass. Despite the fact that such an event is very difficult to imagine from the point of view of an unprepared person, Landau was not far from the truth. The physicist also suggested that, according to the theory of relativity, gravity at such a point will be so great that it will begin to distort space-time.
Astrophysicists liked Landau's theory, and they continued to develop it. In 1939, in America, thanks to the efforts of two physicists - Robert Oppenheimer and Hartland Snyder - a theory emerged that described in detail a supermassive star at the time of collapse. As a result of such an event, a real black hole should have appeared. Despite the convincingness of the arguments, scientists continued to deny the possibility of the existence of such bodies, as well as the transformation of stars into them. Even Einstein distanced himself from this idea, believing that a star was not capable of such phenomenal transformations. Other physicists did not skimp on their statements, calling the possibility of such events absurd.
However, science always reaches the truth, you just have to wait a little. And so it happened.
The brightest objects in the Universe
Our world is a collection of paradoxes. Sometimes things coexist in it, the coexistence of which defies any logic. For example, the term “black hole” would not be associated by a normal person with the expression “incredibly bright,” but a discovery in the early 60s of the last century allowed scientists to consider this statement to be incorrect.
With the help of telescopes, astrophysicists were able to discover hitherto unknown objects in the starry sky, which behaved very strangely despite the fact that they looked like ordinary stars. While studying these strange luminaries, the American scientist Martin Schmidt drew attention to their spectrography, the data of which showed different results from scanning other stars. Simply put, these stars were not like others we are used to.
Suddenly it dawned on Schmidt, and he noticed a shift in the spectrum in the red range. It turned out that these objects are much further from us than the stars that we are used to observing in the sky. For example, the object observed by Schmidt was located two and a half billion light years from our planet, but shone as brightly as a star some hundred light years away. It turns out that the light from one such object is comparable to the brightness of an entire galaxy. This discovery was a real breakthrough in astrophysics. The scientist called these objects “quasi-stellar” or simply “quasar”.
Martin Schmidt continued to study new objects and found that such a bright glow can only be caused by one reason - accretion. Accretion is the process of absorption of surrounding matter by a supermassive body using gravity. The scientist came to the conclusion that at the center of quasars there is a huge black hole, which with incredible force draws in the matter surrounding it in space. As matter is absorbed by the hole, the particles accelerate to enormous speeds and begin to glow. A kind of luminous dome around a black hole is called an accretion disk. Its visualization was well demonstrated in Christopher Nolan's film Interstellar, which gave rise to many questions: “how can a black hole glow?”
To date, scientists have already found thousands of quasars in the starry sky. These strange, incredibly bright objects are called beacons of the Universe. They allow us to imagine the structure of the cosmos a little better and come closer to the moment from which it all began.
Although astrophysicists had been receiving indirect evidence for many years of the existence of supermassive invisible objects in the Universe, the term “black hole” did not exist until 1967. To avoid complex names, American physicist John Archibald Wheeler proposed calling such objects “black holes.” Why not? To some extent they are black, because we cannot see them. Besides, they attract everything, you can fall into them, just like into a real hole. And according to modern laws of physics, it is simply impossible to get out of such a place. However, Stephen Hawking claims that when traveling through a black hole, you can get to another Universe, another world, and this is hope.
Fear of Infinity
Due to the excessive mystery and romanticization of black holes, these objects have become a real horror story among people. The tabloid press loves to speculate on the illiteracy of the population, publishing amazing stories about how a huge black hole is moving towards our Earth, which will devour the Solar system in a matter of hours, or simply emitting waves of toxic gas towards our planet.
The topic of destroying the planet with the help of the Large Hadron Collider, which was built in Europe in 2006 on the territory of the European Council for Nuclear Research (CERN), is especially popular. The wave of panic began as someone's stupid joke, but grew like a snowball. Someone started a rumor that a black hole could form in the particle accelerator of the collider, which would swallow our planet entirely. Of course, the indignant people began to demand a ban on experiments at the LHC, fearing this outcome of events. The European Court began to receive lawsuits demanding that the collider be closed and the scientists who created it punished to the fullest extent of the law.
In fact, physicists do not deny that when particles collide in the Large Hadron Collider, objects similar in properties to black holes can arise, but their size is at the level of the size of elementary particles, and such “holes” exist for such a short time that we can’t even record their occurrence.
One of the main experts who are trying to dispel the wave of ignorance in front of people is Stephen Hawking, a famous theoretical physicist who, moreover, is considered a real “guru” regarding black holes. Hawking proved that black holes do not always absorb the light that appears in the accretion disks, and some of it is scattered into space. This phenomenon was called Hawking radiation, or black hole evaporation. Hawking also established a relationship between the size of a black hole and the rate of its “evaporation” - the smaller it is, the less time it exists. This means that all opponents of the Large Hadron Collider should not worry: black holes in it will not be able to survive even a millionth of a second.
Theory not proven in practice
Unfortunately, human technology at this stage of development does not allow us to test most of the theories developed by astrophysicists and other scientists. On the one hand, the existence of black holes has been quite convincingly proven on paper and deduced using formulas in which everything fits with each variable. On the other hand, in practice we have not yet been able to see a real black hole with our own eyes.
Despite all the disagreements, physicists suggest that in the center of each galaxy there is a supermassive black hole, which gathers stars into clusters with its gravity and forces them to travel around the Universe in a large and friendly company. In our Milky Way galaxy, according to various estimates, there are from 200 to 400 billion stars. All these stars are orbiting something that has enormous mass, something that we can't see with a telescope. It is most likely a black hole. Should we be afraid of her? – No, at least not in the next few billion years, but we can make another interesting film about it.
Black holes, dark matter, dark matter... These are undoubtedly the strangest and most mysterious objects in space. Their bizarre properties can challenge the laws of physics of the Universe and even the nature of existing reality. To understand what black holes are, scientists suggest “changing your focus,” learning to think outside the box and using a little imagination. Black holes are formed from the cores of super massive stars, which can be described as a region of space where enormous mass is concentrated in the void, and nothing, not even light, can escape the gravitational pull there. This is the region where the second escape velocity exceeds the speed of light: And the more massive the object of motion, the faster it must move in order to get rid of the force of its gravity. This is known as escape velocity.
Collier's Encyclopedia calls black holes a region in space that arises as a result of the complete gravitational collapse of matter, in which the gravitational attraction is so strong that neither matter, nor light, nor other information carriers can leave it. Therefore, the interior of a black hole is not causally connected to the rest of the universe; Physical processes occurring inside a black hole cannot influence processes outside it. A black hole is surrounded by a surface with the property of a unidirectional membrane: matter and radiation freely fall through it into the black hole, but nothing can escape from there. This surface is called the “event horizon.”
History of discovery
Black holes, predicted by the general theory of relativity (the theory of gravity proposed by Einstein in 1915) and other, more modern theories of gravity, were mathematically substantiated by R. Oppenheimer and H. Snyder in 1939. But the properties of space and time in the vicinity of these objects turned out to be so unusual, that astronomers and physicists did not take them seriously for 25 years. However, astronomical discoveries in the mid-1960s brought black holes to the surface as a possible physical reality. New discoveries and studies could fundamentally change our understanding of space and time, shedding light on billions of cosmic mysteries.
Formation of black holes
While thermonuclear reactions occur in the bowels of the star, they maintain high temperature and pressure, preventing the star from collapsing under the influence of its own gravity. However, over time, the nuclear fuel is depleted and the star begins to shrink. Calculations show that if the mass of a star does not exceed three solar masses, then it will win the “battle with gravity”: its gravitational collapse will be stopped by the pressure of “degenerate” matter, and the star will forever turn into a white dwarf or neutron star. But if the mass of the star is more than three solar, then nothing can stop its catastrophic collapse and it will quickly go under the event horizon, becoming a black hole.
Is a black hole a donut hole?
What does not emit light is not easy to notice. One way to search for a black hole is to look for regions in outer space that have a lot of mass and are in dark space. When searching for these types of objects, astronomers found them in two main areas: in the centers of galaxies and in the double star systems of our Galaxy. In total, scientists suggest, there are tens of millions of such objects.
Currently, the only reliable way to distinguish a black hole from another type of object is to measure the mass and size of the object and compare its radius with
