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
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Consider the mysterious and invisible black holes in the Universe: interesting facts, Einstein's research, supermassive and intermediate types, theory, structure.
- one of the most interesting and mysterious objects in outer space. They have a high density, and the gravitational force is so powerful that even light cannot escape beyond its limits.
Albert Einstein first spoke about black holes in 1916, when he created the general theory of relativity. The term itself originated in 1967 thanks to John Wheeler. And the first black hole was “seen” in 1971.
The classification of black holes includes three types: stellar mass black holes, supermassive black holes and intermediate mass black holes. Be sure to watch the video about black holes to learn many interesting facts and get to know these mysterious cosmic formations better.
Interesting facts about black holes
- If you find yourself inside a black hole, gravity will stretch you. But there is no need to be afraid, because you will die before you reach the singularity. A 2012 study suggested that quantum effects turn the event horizon into a wall of fire that turns you into a pile of ash.
- Black holes don't "suck". This process is caused by a vacuum, which is not present in this formation. So the material just falls off.
- The first black hole was Cygnus X-1, found by rockets with Geiger counters. In 1971, scientists received a radio signal from Cygnus X-1. This object became the subject of a dispute between Kip Thorne and Stephen Hawking. The latter believed that it was not a black hole. In 1990, he admitted defeat.
- Tiny black holes may have appeared immediately after the Big Bang. Rapidly rotating space compressed some areas into dense holes, less massive than the Sun.
- If the star gets too close, it could be torn apart.
- It is generally estimated that there are up to a billion stellar black holes with three times the mass of the Sun.
- If we compare string theory and classical mechanics, the former gives rise to more varieties of massive giants.
The danger of black holes
When a star runs out of fuel, it can begin the process of self-destruction. If its mass was three times that of the Sun, then the remaining core would become a neutron star or white dwarf. But the larger star transforms into a black hole.
Such objects are small, but have incredible density. Imagine that in front of you is an object the size of a city, but its mass is three times that of the Sun. This creates an incredibly huge gravitational force that attracts dust and gas, increasing its size. You will be surprised, but there may be several hundred million stellar black holes.
Supermassive black holes
Of course, nothing in the universe compares to the awesomeness of supermassive black holes. They exceed the solar mass by billions of times. It is believed that such objects exist in almost every galaxy. Scientists do not yet know all the intricacies of the formation process. Most likely, they grow due to the accumulation of mass from surrounding dust and gas.
They may owe their scale to the merger of thousands of small black holes. Or an entire star cluster could collapse.
Black holes at the centers of galaxies
Astrophysicist Olga Silchenko about the discovery of a supermassive black hole in the Andromeda nebula, John Kormendy's research and dark gravitating bodies:
The nature of cosmic radio sources
Astrophysicist Anatoly Zasov about synchrotron radiation, black holes in the nuclei of distant galaxies and neutral gas:
Intermediate black holes
Not long ago, scientists found a new type - intermediate mass black holes. They can form when stars in a cluster collide, causing a chain reaction. As a result, they fall into the center and form a supermassive black hole.
In 2014, astronomers discovered an intermediate type in the arm of a spiral galaxy. They are very difficult to find because they can be located in unpredictable places.
Micro black holes
Physicist Eduard Boos on the safety of the LHC, the birth of a microblack hole and the concept of a membrane:
Black hole theory
Black holes are extremely massive objects, but span a relatively modest amount of space. In addition, they have enormous gravity, preventing objects (and even light) from leaving their territory. However, it is impossible to see them directly. Researchers have to look at the radiation produced when a black hole feeds.
Interestingly, it happens that matter heading towards a black hole bounces off the event horizon and is thrown out. In this case, bright jets of material are formed, moving at relativistic speeds. These emissions can be detected over long distances.
- amazing objects in which the force of gravity is so enormous that it can bend light, warp space and distort time.
In black holes, three layers can be distinguished: the outer and inner event horizon and the singularity.
The event horizon of a black hole is the boundary where light has no chance of escaping. Once a particle crosses this line, it will not be able to leave. The inner region where the mass of a black hole is located is called a singularity.
If we speak from the position of classical mechanics, then nothing can escape a black hole. But quantum makes its own correction. The fact is that every particle has an antiparticle. They have the same masses, but different charges. If they intersect, they can annihilate each other.
When such a pair appears outside the event horizon, one of them can be pulled in and the other can be repelled. Because of this, the horizon can shrink and the black hole can collapse. Scientists are still trying to study this mechanism.
Accretion
Astrophysicist Sergei Popov on supermassive black holes, planet formation and accretion of matter in the early Universe:
The most famous black holes
Frequently asked questions about black holes
More capaciously, a black hole is a certain area in space in which such a huge amount of mass is concentrated that not a single object can escape the gravitational influence. When it comes to gravity, we rely on the general theory of relativity proposed by Albert Einstein. To understand the details of the object under study, we will move step by step.
Let's imagine that you are on the surface of the planet and are throwing a boulder. If you don't have the power of the Hulk, you won't be able to exert enough force. Then the stone will rise to a certain height, but under the pressure of gravity it will fall back. If you have the hidden potential of a green strongman, then you are able to give the object sufficient acceleration, thanks to which it will completely leave the zone of gravitational influence. This is called "escape velocity".
If we break it down into a formula, this speed depends on the planetary mass. The larger it is, the more powerful the gravitational grip. The speed of departure will depend on where exactly you are: the closer to the center, the easier it is to get out. The speed of departure of our planet is 11.2 km/s, but it is 2.4 km/s.
We are getting closer to the most interesting part. Let's say you have an object with an incredible concentration of mass collected in a tiny place. In this case, the escape velocity exceeds the speed of light. And we know that nothing moves faster than this indicator, which means that no one will be able to overcome such force and escape. Even a light beam cannot do this!
Back in the 18th century, Laplace pondered the extreme concentration of mass. Following general relativity, Karl Schwarzschild was able to find a mathematical solution to the theory's equation to describe such an object. Further contributions were made by Oppenheimer, Wolkoff and Snyder (1930s). From that moment on, people began to discuss this topic seriously. It became clear: when a massive star runs out of fuel, it is unable to withstand the force of gravity and is bound to collapse into a black hole.
In Einstein's theory, gravity is a manifestation of curvature in space and time. The fact is that the usual geometric rules do not work here and massive objects distort space-time. The black hole has bizarre properties, so its distortion is most clearly visible. For example, an object has an “event horizon”. This is the surface of the sphere marking the line of the hole. That is, if you step over this limit, then there is no turning back.
Literally, this is the place where the escape speed is equal to the speed of light. Outside this place, the escape velocity is inferior to the speed of light. But if your rocket is able to accelerate, then there will be enough energy to escape.
The horizon itself is quite strange in terms of geometry. If you are far away, you will feel like you are looking at a static surface. But if you get closer, you realize that it is moving outward at the speed of light! Now I understand why it is easy to enter, but so difficult to escape. Yes, this is very confusing, because in fact the horizon stands still, but at the same time it rushes at the speed of light. It's like the situation with Alice, who had to run as fast as possible just to stay in place.
When hitting the horizon, space and time experience such a strong distortion that the coordinates begin to describe the roles of radial distance and switching time. That is, “r”, marking the distance from the center, becomes temporary, and “t” is now responsible for “spatiality”. As a result, you will not be able to stop moving with a lower index of r, just as you will not be able to get into the future in normal time. You will come to a singularity where r = 0. You can throw rockets, run the engine to maximum, but you cannot escape.
The term "black hole" was coined by John Archibald Wheeler. Before that, they were called “cooled stars.”
Physicist Emil Akhmedov on the study of black holes, Karl Schwarzschild and giant black holes:
There are two ways to calculate how big something is. You can name the mass or how large the area occupies. If we take the first criterion, then there is no specific limit on the massiveness of a black hole. You can use any amount as long as you can compress it to the required density.
Most of these formations appeared after the death of massive stars, so one would expect that their weight should be equivalent. The typical mass for such a hole would be 10 times that of the sun - 10 31 kg. In addition, each galaxy must be home to a central supermassive black hole, whose mass exceeds the solar one a million times - 10 36 kg.
The more massive the object, the more mass it covers. The horizon radius and mass are directly proportional, that is, if a black hole weighs 10 times more than another, then its radius is 10 times larger. The radius of a hole with solar massiveness is 3 km, and if it is a million times larger, then 3 million km. These seem to be incredibly massive things. But let's not forget that these are standard concepts for astronomy. The solar radius reaches 700,000 km, and that of a black hole is 4 times larger.
Let's say that you are unlucky and your ship is inexorably moving towards a supermassive black hole. There's no point in fighting. You simply turn off the engines and head towards the inevitable. What to expect?
Let's start with weightlessness. You are in free fall, so the crew, ship and all the parts are weightless. The closer you get to the center of the hole, the stronger the tidal gravitational forces are felt. For example, your feet are closer to the center than your head. Then you begin to feel like you are being stretched. As a result, you will simply be torn apart.
These forces are unnoticeable until you get within 600,000 km of the center. This is already after the horizon. But we are talking about a huge object. If you fall into a hole with the mass of the sun, then the tidal forces would engulf you 6000 km from the center and tear you apart before you reach the horizon (that's why we send you to the big one so that you can die already inside the hole, and not on the approach) .
What's inside? I don't want to disappoint, but nothing remarkable. Some objects may be distorted in appearance and nothing else out of the ordinary. Even after crossing the horizon, you will see things around you as they move with you.
How long will all this take? Everything depends on your distance. For example, you started from a point of rest where the singularity is 10 times the radius of the hole. It will take only 8 minutes to approach the horizon, and then another 7 seconds to enter the singularity. If you fall into a small black hole, everything will happen faster.
As soon as you cross the horizon, you can shoot rockets, scream and cry. You have 7 seconds to do all this until you get into the singularity. But nothing will save you. So just enjoy the ride.
Let's say you are doomed and fall into a hole, and your boyfriend watches from afar. Well, he'll see things differently. You will notice that you slow down as you get closer to the horizon. But even if a person sits for a hundred years, he will not wait until you reach the horizon.
Let's try to explain. The black hole could have emerged from a collapsing star. Since the material is destroyed, Kirill (let him be your friend) sees it decreasing, but will never notice it approaching the horizon. That's why they were called "frozen stars" because they seem to freeze at a certain radius.
What's the matter? Let's call it an optical illusion. Infinity is not needed to form a hole, just as it is not necessary to cross the horizon. As you approach, the light takes longer to reach Kirill. More precisely, the real-time radiation from your transition will be recorded at the horizon forever. You have long stepped over the line, and Kirill is still observing the light signal.
Or you can approach from the other side. Time drags longer near the horizon. For example, you have a super-powerful ship. You managed to get closer to the horizon, stay there for a couple of minutes and get out alive to Kirill. Who will you see? Old man! After all, time passed much slower for you.
What is true then? Illusion or game of time? It all depends on the coordinate system used to describe the black hole. If you rely on Schwarzschild coordinates, then when crossing the horizon, the time coordinate (t) is equated to infinity. But the system's metrics provide a blurred view of what's happening near the object itself. At the horizon line, all coordinates are distorted (singularity). But you can use both coordinate systems, so the two answers are valid.
In reality, you will simply become invisible, and Kirill will stop seeing you before much time has passed. Don't forget about redshift. You emit observable light at a certain wavelength, but Kirill will see it at a longer one. The waves lengthen as they approach the horizon. In addition, do not forget that radiation occurs in certain photons.
For example, at the moment of transition you will send the last photon. It will reach Kirill at a certain finite time (about an hour for a supermassive black hole).
Of course not. Don't forget about the existence of the event horizon. This is the only area you can't get out of. It is enough just not to approach her and feel calm. Moreover, from a safe distance this object will seem very ordinary to you.
Hawking's information paradox
Physicist Emil Akhmedov on the effect of gravity on electromagnetic waves, the information paradox of black holes and the principle of predictability in science:
Don't panic, as the Sun will never transform into such an object because it simply doesn't have enough mass. Moreover, it will retain its current appearance for another 5 billion years. Then it will move to the red giant stage, absorbing Mercury, Venus and thoroughly frying our planet, and then become an ordinary white dwarf.
But let's indulge in fantasy. So the Sun became a black hole. To begin with, we will immediately be enveloped in darkness and cold. The Earth and other planets will not be sucked into the hole. They will continue to orbit the new object in normal orbits. Why? Because the horizon will reach only 3 km, and gravity will not be able to do anything to us.
Yes. Naturally, we cannot rely on visible observation, since the light cannot escape. But there is circumstantial evidence. For example, you see an area that could contain a black hole. How can I check this? Start by measuring the mass. If it is clear that in one area there is too much of it or it is seemingly invisible, then you are on the right track. There are two search points: the galactic center and binary systems with X-ray radiation.
Thus, massive central objects were found in 8 galaxies, whose nuclear mass ranges from a million to a billion solar. Mass is calculated by observing the speed of rotation of stars and gas around the center. The faster, the greater the mass must be to keep them in orbit.
These massive objects are considered black holes for two reasons. Well, there are simply no more options. There is nothing more massive, darker and more compact. In addition, there is a theory that all active and large galaxies have such a monster hiding in the center. But still this is not 100% proof.
But two recent findings speak in favor of the theory. A “water maser” system (a powerful source of microwave radiation) near the nucleus was noticed in the nearest active galaxy. Using an interferometer, scientists mapped the distribution of gas velocities. That is, they measured the speed within half a light year at the galactic center. This helped them understand that there was a massive object inside, whose radius reached half a light year.
The second find is even more convincing. Researchers using X-rays stumbled upon a spectral line of the galactic core, indicating the presence of atoms nearby, the speed of which is incredibly high (1/3 the speed of light). In addition, the emission corresponded to a redshift that corresponds to the horizon of the black hole.
Another class can be found in the Milky Way. These are stellar black holes that form after a supernova explosion. If they existed separately, then even close up we would hardly notice it. But we are lucky, because most exist in dual systems. They are easy to find, since the black hole will pull the mass of its neighbor and influence it with gravity. The “pulled out” material forms an accretion disk, in which everything heats up and therefore creates strong radiation.
Let's assume you managed to find a binary system. How do you understand that a compact object is a black hole? Again we turn to the masses. To do this, measure the orbital speed of a nearby star. If the mass is incredibly huge with such small dimensions, then there are no more options left.
This is a complex mechanism. Stephen Hawking raised a similar topic back in the 1970s. He said that black holes are not really “black.” There are quantum mechanical effects that cause it to create radiation. Gradually the hole begins to shrink. The rate of radiation increases with decreasing mass, so the hole emits more and more and accelerates the process of contraction until it dissolves.
However, this is only a theoretical scheme, because no one can say exactly what happens at the last stage. Some people think that a small but stable trace remains. Modern theories have not yet come up with anything better. But the process itself is incredible and complex. It is necessary to calculate parameters in curved space-time, and the results themselves cannot be verified under normal conditions.
The Law of Conservation of Energy can be used here, but only for short durations. The universe can create energy and mass from scratch, but they must quickly disappear. One of the manifestations is vacuum fluctuations. Pairs of particles and antiparticles grow out of nowhere, exist for a certain short period of time and die in mutual destruction. When they appear, the energy balance is disrupted, but everything is restored after disappearance. It seems fantastic, but this mechanism has been confirmed experimentally.
Let's say one of the vacuum fluctuations acts near the horizon of a black hole. Perhaps one of the particles falls in, and the second runs away. The one who escapes takes some of the energy of the hole with her and can fall into the eyes of the observer. It will seem to him that a dark object has simply released a particle. But the process repeats itself, and we see a continuous stream of radiation from the black hole.
We've already said that Kirill feels like you need infinity to step over the horizon line. In addition, it was mentioned that black holes evaporate after a finite period of time. So, when you reach the horizon, the hole will disappear?
No. When we described Kirill's observations, we did not talk about the evaporation process. But, if this process is present, then everything changes. Your friend will see you fly across the horizon at the exact moment of evaporation. Why?
An optical illusion dominates Kirill. The emitted light in the event horizon takes a long time to reach its friend. If the hole lasts forever, then the light can travel indefinitely, and Kirill will not wait for the transition. But, if the hole has evaporated, then nothing will stop the light, and it will get to the guy at the moment of the explosion of radiation. But you don’t care anymore, because you died in the singularity long ago.
The formulas of the general theory of relativity have an interesting feature - symmetry in time. For example, in any equation you can imagine that time flows backwards and get a different, but still correct, solution. If we apply this principle to black holes, then a white hole is born.
A black hole is a defined area from which nothing can escape. But the second option is a white hole into which nothing can fall. In fact, she pushes everything away. Although, from a mathematical point of view, everything looks smooth, this does not prove their existence in nature. Most likely, there are none, and there is no way to find out.
Up to this point we have talked about the classics of black holes. They do not rotate and have no electrical charge. But in the opposite version, the most interesting thing begins. For example, you can get inside but avoid the singularity. Moreover, its “inside” is capable of contacting a white hole. That is, you will find yourself in a kind of tunnel, where the black hole is the entrance and the white hole is the exit. This combination is called a wormhole.
Interestingly, a white hole can be located anywhere, even in another Universe. If we know how to control such wormholes, then we will provide rapid transportation to any area of space. And even cooler is the possibility of time travel.
But don't pack your backpack until you know a few things. Unfortunately, there is a high probability that there are no such formations. We have already said that white holes are a conclusion from mathematical formulas, and not a real and confirmed object. And all observed black holes create matter falling and do not form wormholes. And the final stop is the singularity.
Have you ever seen a floor being vacuumed? If so, have you noticed how the vacuum cleaner sucks up dust and small debris like scraps of paper? Of course they noticed. Black holes do much the same thing as a vacuum cleaner, but instead of dust, they prefer to suck in larger objects: stars and planets. However, they will not disdain cosmic dust either.
How do black holes appear?
To understand where black holes come from, it would be nice to know what light pressure is. It turns out that light falling on objects puts pressure on them. For example, if we light a light bulb in a dark room, then an additional light pressure force will begin to act on all illuminated objects. This force is very small, and in everyday life we, of course, will never be able to feel it. The reason is that a light bulb is a very weak light source. (In laboratory conditions, the light pressure of a light bulb can still be measured; the Russian physicist P. N. Lebedev was the first to do this) With stars, the situation is different. While the star is young and shining brightly, three forces are fighting inside it. On the one hand, the force of gravity, which tends to compress the star into a point, pulls the outer layers inward towards the core. On the other hand, there is the force of light pressure and the pressure force of hot gas, tending to inflate the star. The light produced in the star's core is so intense that it pushes away the outer layers of the star and balances the force of gravity pulling them toward the center. As a star ages, its core produces less and less light. This happens because during the life of a star, its entire supply of hydrogen burns out, we have already written about this. If the star is very large, 20 times heavier than the Sun, then its outer shells are very large in mass. Therefore, in a heavy star, the outer layers begin to move closer and closer to the core, and the entire star begins to contract. At the same time, the gravitational force on the surface of the contracting star increases. The more a star contracts, the more it begins to attract the surrounding matter. Eventually, the star's gravity becomes so monstrously strong that even the light it emits cannot escape. At this moment the star becomes a black hole. It no longer emits anything, but only absorbs everything that is nearby, including light. Not a single ray of light comes from it, so no one can see it, and that’s why it’s called a black hole: everything gets sucked in and never comes back.
What does a black hole look like?
If you and I were next to a black hole, we would see a fairly large luminous disk rotating around a small, completely black region of space. This black region is a black hole. And the luminous disk around it is matter falling into the black hole. Such a disk is called an accretion disk. The gravity of a black hole is very strong, so the matter sucked inside moves with very high acceleration and because of this it begins to radiate. By studying the light coming from such a disk, astronomers can learn a lot about the black hole itself. Another indirect sign of the existence of a black hole is the unusual movement of stars around a certain region of space. The hole's gravity forces nearby stars to move in elliptical orbits. Such movements of stars are also recorded by astronomers.
Now the attention of scientists is focused on the black hole located at the center of our galaxy. The fact is that a cloud of hydrogen with a mass about 3 times that of Earth is approaching the black hole. This cloud has already begun to change its shape due to the gravity of the black hole, in the coming years it will stretch even more and will be pulled inside the black hole.
We will never be able to see the processes occurring inside a black hole, so we can only be content with observing the disk around the black hole. But a lot of interesting things await us here too. Perhaps the most interesting phenomenon is the formation of ultrafast jets of matter escaping from the center of this disk. The mechanism of this phenomenon remains to be elucidated, and it is quite possible that one of you will create a theory for the formation of such jets. For now, we can only register the X-ray flashes that accompany such “shots.”
This video shows how a black hole gradually captures material from a nearby star. In this case, an accretion disk is formed around the black hole, and part of its matter is ejected into space at enormous speeds. This generates a large amount of X-ray radiation, which is picked up by a satellite moving around the Earth.
How does a black hole work?
A black hole can be divided into three main parts. The outer part, being in which you can still avoid falling into a black hole if you move at very high speed. Deeper than the outer part there is an event horizon - this is an imaginary boundary, after crossing which the body loses all hope of returning from the black hole. Everything that is beyond the event horizon cannot be seen from the outside, because due to strong gravity, even light moving from inside will not be able to fly beyond it. It is believed that at the very center of a black hole there is a singularity - a region of space of a tiny volume in which a huge mass is concentrated - the heart of the black hole.
Is it possible to fly up to a black hole?
At a great distance, the attraction of a black hole is exactly the same as the attraction of an ordinary star with the same mass as the black hole. As you approach the event horizon, the attraction will grow stronger and stronger. Therefore, you can fly up to a black hole, but it is better to stay away from it so that you can return back. Astronomers had to watch how a black hole sucked a nearby star inside. You can see what it looked like in this video:
Will our Sun turn into a black hole?
No, it won't turn. The mass of the Sun is too small for this. Calculations show that in order to become a black hole, a star must be at least 4 times more massive than the Sun. Instead, the Sun will become a red giant and inflate to about the size of Earth's orbit before shedding its outer shell and becoming a white dwarf. We will definitely tell you more about the evolution of the Sun.
Of all the objects known to mankind that are located in outer space, black holes produce the most eerie and incomprehensible impression. This feeling covers almost every person when black holes are mentioned, despite the fact that humanity has known about them for more than a century and a half. The first knowledge about these phenomena was obtained long before Einstein’s publications on the theory of relativity. But real confirmation of the existence of these objects was received not so long ago.
Of course, black holes are rightfully famous for their strange physical characteristics, which give rise to even more mysteries in the Universe. They easily challenge all cosmic laws of physics and cosmic mechanics. In order to understand all the details and principles of the existence of such a phenomenon as a cosmic hole, we need to familiarize ourselves with modern achievements in astronomy and use our imagination; in addition, we will have to go beyond standard concepts. To make it easier to understand and get acquainted with cosmic holes, the portal site has prepared a lot of interesting information regarding these phenomena in the Universe.
Features of black holes from the portal site
First of all, it should be noted that black holes do not come out of nowhere, they are formed from stars that are gigantic in size and mass. Moreover, the biggest feature and uniqueness of every black hole is that they have a very strong gravitational pull. The force of attraction of objects to a black hole exceeds the second escape velocity. Such gravity indicators indicate that even light rays cannot escape from the field of action of a black hole, since they have a much lower speed.
The peculiarity of attraction is that it attracts all objects that are in close proximity. The larger the object that passes in the vicinity of the black hole, the more influence and attraction it will receive. Accordingly, we can conclude that the larger the object, the stronger it is attracted by the black hole, and in order to avoid such influence, the cosmic body must have very high speed rates of movement.
It is also safe to note that in the entire Universe there is no body that could avoid the attraction of a black hole if it finds itself in close proximity, since even the fastest light stream cannot escape this influence. The theory of relativity, developed by Einstein, is excellent for understanding the characteristics of black holes. According to this theory, gravity can influence time and distort space. It also states that the larger an object located in outer space, the more it slows down time. In the vicinity of the black hole itself, time seems to stop completely. If a spacecraft were to enter the field of action of a space hole, one would observe how it would slow down as it approached, and ultimately disappear altogether.
You shouldn’t be too scared of phenomena such as black holes and believe all the unscientific information that may exist at the moment. First of all, we need to dispel the most common myth that black holes can suck in all the matter and objects around them, and as they do so, they grow and absorb more and more. None of this is entirely true. Yes, indeed, they can absorb cosmic bodies and matter, but only those that are at a certain distance from the hole itself. Apart from their powerful gravity, they are not much different from ordinary stars with gigantic mass. Even when our Sun turns into a black hole, it will only be able to suck in objects located at a short distance, and all the planets will remain rotating in their usual orbits.
Turning to the theory of relativity, we can conclude that all objects with strong gravity can influence the curvature of time and space. In addition, the greater the body mass, the stronger the distortion will be. So, quite recently, scientists were able to see this in practice, when they could contemplate other objects that should have been inaccessible to our eyes due to huge cosmic bodies such as galaxies or black holes. All this is possible due to the fact that light rays passing nearby from a black hole or other body are very strongly bent under the influence of their gravity. This type of distortion allows scientists to look much further into outer space. But with such studies it is very difficult to determine the real location of the body being studied.
Black holes don't appear out of nowhere; they are formed by the explosion of supermassive stars. Moreover, in order for a black hole to form, the mass of the exploded star must be at least ten times greater than the mass of the Sun. Each star exists due to thermonuclear reactions that take place inside the star. In this case, a hydrogen alloy is released during the fusion process, but it cannot leave the star’s zone of action, since its gravity attracts the hydrogen back. This whole process allows stars to exist. Hydrogen synthesis and star gravity are fairly well-functioning mechanisms, but disruption of this balance can lead to a star explosion. In most cases, it is caused by the exhaustion of nuclear fuel.
Depending on the mass of the star, several scenarios for their development after the explosion are possible. Thus, massive stars form the field of a supernova explosion, and most of them remain behind the core of the former star; astronauts call such objects White Dwarfs. In most cases, a gas cloud forms around these bodies, which is held in place by the gravity of the dwarf. Another path for the development of supermassive stars is also possible, in which the resulting black hole will very strongly attract all the matter of the star to its center, which will lead to its strong compression.
Such compressed bodies are called neutron stars. In the rarest cases, after the explosion of a star, the formation of a black hole in our accepted understanding of this phenomenon is possible. But for a hole to be created, the mass of the star must be simply gigantic. In this case, when the balance of nuclear reactions is disrupted, the gravity of the star simply goes crazy. At the same time, it begins to actively collapse, after which it becomes only a point in space. In other words, we can say that the star as a physical object ceases to exist. Despite the fact that it disappears, a black hole with the same gravity and mass is formed behind it.
It is the collapse of stars that leads to the fact that they completely disappear, and in their place a black hole is formed with the same physical properties as the disappeared star. The only difference is the greater degree of compression of the hole than the volume of the star. The most important feature of all black holes is their singularity, which determines its center. This area defies all laws of physics, matter and space, which cease to exist. To understand the concept of singularity, we can say that this is a barrier that is called the cosmic event horizon. It is also the outer boundary of the black hole. The singularity can be called the point of no return, since it is there that the gigantic gravitational force of the hole begins to act. Even the light that crosses this barrier is unable to escape.
The event horizon has such an attractive effect that attracts all bodies at the speed of light; as you approach the black hole itself, the speed indicators increase even more. That is why all objects that fall within the range of this force are doomed to be sucked into the hole. It should be noted that such forces are capable of modifying a body caught by the action of such attraction, after which they stretch into a thin string, and then completely cease to exist in space.
The distance between the event horizon and the singularity can vary; this space is called the Schwarzschild radius. That is why the larger the size of the black hole, the larger the range of action will be. For example, we can say that a black hole that was as massive as our Sun would have a Schwarzschild radius of three kilometers. Accordingly, large black holes have a larger range.
Finding black holes is a rather difficult process, since light cannot escape from them. Therefore, the search and definition are based only on indirect evidence of their existence. The simplest method that scientists use to find them is to search for them by finding places in dark space if they have a large mass. In most cases, astronomers manage to find black holes in binary star systems or in the centers of galaxies.
Most astronomers tend to believe that there is also a super-powerful black hole at the center of our galaxy. This statement begs the question, will this hole be able to swallow everything in our galaxy? In reality this is impossible, since the hole itself has the same mass as the stars, because it is created from the star. Moreover, all scientists’ calculations do not foretell any global events related to this object. Moreover, for another billions of years, the cosmic bodies of our galaxy will quietly rotate around this black hole without any changes. Evidence of the existence of a hole in the center of the Milky Way can come from the X-ray waves recorded by scientists. And most astronomers are inclined to believe that black holes actively emit them in huge quantities.
Quite often in our galaxy there are star systems consisting of two stars, and often one of them can become a black hole. In this version, the black hole absorbs all bodies in its path, while matter begins to rotate around it, due to which the so-called acceleration disk is formed. A special feature is that it increases the rotation speed and moves closer to the center. It is the matter that falls into the middle of the black hole that emits X-rays, and the matter itself is destroyed.
Binary star systems are the very first candidates for black hole status. In such systems it is most easy to find a black hole; due to the volume of the visible star, it is possible to calculate the indicators of its invisible brother. Currently, the very first candidate for the status of a black hole may be a star from the constellation Cygnus, which actively emits X-rays.
Concluding from all of the above about black holes, we can say that they are not such dangerous phenomena; of course, in the case of close proximity, they are the most powerful objects in outer space due to the force of gravity. Therefore, we can say that they are not particularly different from other bodies; their main feature is a strong gravitational field.
A huge number of theories have been proposed regarding the purpose of black holes, some of which were even absurd. Thus, according to one of them, scientists believed that black holes can give birth to new galaxies. This theory is based on the fact that our world is a fairly favorable place for the origin of life, but if one of the factors changes, life would be impossible. Because of this, the singularity and peculiarities of changes in physical properties in black holes can give rise to a completely new Universe, which will be significantly different from ours. But this is only a theory and a rather weak one due to the fact that there is no evidence of such an effect of black holes.
As for black holes, not only can they absorb matter, but they can also evaporate. A similar phenomenon was proven several decades ago. This evaporation can cause the black hole to lose all its mass and then disappear altogether.
All this is the smallest piece of information about black holes that you can find out on the portal website. We also have a huge amount of interesting information about other cosmic phenomena.
The concept of a black hole is known to everyone - from schoolchildren to the elderly; it is used in science and fiction literature, in the yellow media and at scientific conferences. But what exactly such holes are is not known to everyone.
From the history of black holes
1783 The first hypothesis of the existence of such a phenomenon as a black hole was put forward in 1783 by the English scientist John Michell. In his theory, he combined two of Newton's creations - optics and mechanics. Michell's idea was this: if light is a stream of tiny particles, then, like all other bodies, the particles should experience the attraction of a gravitational field. It turns out that the more massive the star, the more difficult it is for light to resist its attraction. 13 years after Michell, the French astronomer and mathematician Laplace put forward (most likely independently of his British colleague) a similar theory.
1915 However, all their works remained unclaimed until the beginning of the 20th century. In 1915, Albert Einstein published the General Theory of Relativity and showed that gravity is the curvature of spacetime caused by matter, and a few months later, German astronomer and theoretical physicist Karl Schwarzschild used it to solve a specific astronomical problem. He explored the structure of curved space-time around the Sun and rediscovered the phenomenon of black holes.
(John Wheeler coined the term "Black holes")
1967 American physicist John Wheeler outlined a space that can be crumpled, like a piece of paper, into an infinitesimal point and designated it with the term “Black Hole”.
1974 British physicist Stephen Hawking proved that black holes, although they absorb matter without return, can emit radiation and eventually evaporate. This phenomenon is called “Hawking radiation”.
Our time. The latest research into pulsars and quasars, as well as the discovery of cosmic microwave background radiation, has finally made it possible to describe the very concept of black holes. In 2013, the G2 gas cloud came very close to the Black Hole and will most likely be swallowed up by it, observing the unique process will provide enormous opportunities for new discoveries of the features of black holes.
What black holes actually are
A laconic explanation of the phenomenon goes like this. A black hole is a space-time region whose gravitational attraction is so strong that no object, including light quanta, can leave it.
The black hole was once a massive star. As long as thermonuclear reactions maintain high pressure in its depths, everything remains normal. But over time, the energy supply is depleted and the celestial body, under the influence of its own gravity, begins to shrink. The final stage of this process is the collapse of the stellar core and the formation of a black hole.
- 1. A black hole ejects a jet at high speed
- 2. A disk of matter grows into a black hole
- 3. Black hole
- 4. Detailed diagram of the black hole region
- 5. Size of new observations found
The most common theory is that similar phenomena exist in every galaxy, including the center of our Milky Way. The huge gravitational force of the hole is capable of holding several galaxies around it, preventing them from moving away from each other. The “coverage area” can be different, it all depends on the mass of the star that turned into a black hole, and can be thousands of light years.
Schwarzschild radius
The main property of a black hole is that any substance that falls into it can never return. The same applies to light. At their core, holes are bodies that completely absorb all light falling on them and do not emit any of their own. Such objects may visually appear as clots of absolute darkness.
- 1. Moving matter at half the speed of light
- 2. Photon ring
- 3. Inner photon ring
- 4. Event horizon in a black hole
Based on Einstein's General Theory of Relativity, if a body approaches a critical distance to the center of the hole, it will no longer be able to return. This distance is called the Schwarzschild radius. What exactly happens inside this radius is not known for certain, but there is the most common theory. It is believed that all the matter of a black hole is concentrated in an infinitesimal point, and at its center there is an object with infinite density, which scientists call a singular disturbance.
How does falling into a black hole happen?
(In the picture, the black hole Sagittarius A* looks like an extremely bright cluster of light)
Not so long ago, in 2011, scientists discovered a gas cloud, giving it the simple name G2, which emits unusual light. This glow may be due to friction in the gas and dust caused by the Sagittarius A* black hole, which orbits it as an accretion disk. Thus, we become observers of the amazing phenomenon of absorption of a gas cloud by a supermassive black hole.
According to recent studies, the closest approach to the black hole will occur in March 2014. We can recreate a picture of how this exciting spectacle will take place.
- 1. When first appearing in the data, a gas cloud resembles a huge ball of gas and dust.
- 2. Now, as of June 2013, the cloud is tens of billions of kilometers from the black hole. It falls into it at a speed of 2500 km/s.
- 3. The cloud is expected to pass by the black hole, but tidal forces caused by the difference in gravity acting on the leading and trailing edges of the cloud will cause it to take on an increasingly elongated shape.
- 4. After the cloud is torn apart, most of it will most likely flow into the accretion disk around Sagittarius A*, generating shock waves in it. The temperature will jump to several million degrees.
- 5. Part of the cloud will fall directly into the black hole. No one knows exactly what will happen to this substance next, but it is expected that as it falls it will emit powerful streams of X-rays and will never be seen again.
Video: black hole swallows a gas cloud
(Computer simulation of how much of the G2 gas cloud would be destroyed and consumed by the black hole Sagittarius A*)
What's inside a black hole?
There is a theory that states that a black hole is practically empty inside, and all its mass is concentrated in an incredibly small point located at its very center - the singularity.
According to another theory, which has existed for half a century, everything that falls into a black hole passes into another universe located in the black hole itself. Now this theory is not the main one.
And there is a third, most modern and tenacious theory, according to which everything that falls into a black hole dissolves in the vibrations of strings on its surface, which is designated as the event horizon.
So what is an event horizon? It is impossible to look inside a black hole even with a super-powerful telescope, since even light, entering the giant cosmic funnel, has no chance of emerging back. Everything that can be at least somehow considered is located in its immediate vicinity.
The event horizon is a conventional surface line from under which nothing (neither gas, nor dust, nor stars, nor light) can escape. And this is the very mysterious point of no return in the black holes of the Universe.
