Black holes. Can you see a black hole
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Yes, there are. Black hole called a region of space-time in which the gravitational field is so strong that even light cannot leave this region. This happens if the size of the body is less than its gravitational radius rg.
What it is?
Black holes must arise from a very strong mass compression, while the gravitational field increases so strongly that it does not emit light or any other radiation. To overcome gravity and escape from the black hole, it would take second space velocity- more light. But, according to the theory of relativity, no body can develop a speed greater than the speed of light. Therefore, nothing can fly out of a black hole. Information cannot come from there either. It is impossible to know what happened to the one who fell into the black hole. Already near the holes, the properties of space and time change dramatically.
The theoretical possibility of the existence of such regions of space-time follows from some exact solutions of the Einstein equations. Simply put, Einstein predicted amazing properties of black holes, of which the most important is the presence of an event horizon in the black hole. According to the latest observational data, black holes do exist and have amazing properties. The existence of black holes follows from the theory of gravity: if this theory is correct, then the existence of black holes is true. Therefore, statements about direct evidence of the existence of black holes should be understood in the sense of confirming the existence of astronomical objects, so dense and massive, as well as having some other observable properties that they can be interpreted as black holes of general relativity. In addition, black holes are often called objects that do not strictly correspond to the above definition, but only those approaching in their properties to such a black hole - for example, they can be collapsing stars in the late stages of collapse.
Non-rotating black hole
For a non-rotating black hole, the radius of the event horizon coincides with the gravitational radius. At the event horizon for an outside observer, the passage of time stops. A spacecraft sent to a black hole, from the point of view of a distant observer, will never cross the event horizon, but will continuously slow down as it approaches it. Everything that happens under the event horizon, inside the black hole, cannot be seen by an external observer. An astronaut in his spacecraft is, in principle, capable of penetrating the event horizon, but he will not be able to convey any information to an external observer. At the same time, an astronaut freely falling under the event horizon will probably see another universe and even his own future. This is due to the fact that inside the black hole the spatial and temporal coordinates change places, and travel in space is here replaced by travel in time.
Spinning black hole
Its properties are even more amazing. Their event horizon has a smaller radius, it is immersed in the ergosphere - a region of space-time in which bodies must continuously move, picked up by the vortex gravitational field of a rotating black hole.
These unusual properties of black holes seem simply fantastic, so their existence in nature is often questioned.
A black hole in a binary star system
In this case, the effects of the black hole are most pronounced, since in a binary star system, one star is a bright giant, and the other is a black hole. Gas from the shell of the giant star flows out to the black hole, swirls around it, forming a disk. Layers of gas in the disk in spiral orbits approach the black hole and fall into it. But before falling at the edge of the black hole, the gas heats up as a result of friction to a huge temperature of millions of degrees and emits in the X-ray range. From this X-ray emission, black holes are found in binary stellar systems.
Conclusion
Massive black holes are thought to arise at the centers of compact star clusters. Perhaps the X-ray source in the constellation Cygnus, Cygnus-X-1, is such a black hole.
Astronomers do not exclude that in the past, black holes could arise at the beginning of the expansion of the Universe, so the formation of very small black holes is possible.
The values of the masses of a large number of neutron stars and black holes confirm the validity of the predictions of A. Einstein's theory of relativity. In recent years, the problem of the hypothesis of black holes in the Universe has become an observational reality. This means a qualitatively new stage in the study of black holes and their amazing properties, there is hope for new discoveries in this area.
2007-09-12 / Vladimir Pokrovsky
Black holes die before they are even born. At least that's what the American theoretical physicists from Case Western Reserve University in Ohio state. They came up with mathematical formulas that imply that black holes simply cannot form. If these formulas are correct, then perhaps the most important cosmological construction of the 20th century collapses.
What is a black hole? We all know, this has been reported to us many times. This is such a supermassive body, the gravity of which is simply terrible. As soon as something approaches it at a distance from the center, called the event horizon, then everything is never anything, be it a material body, be it just a quantum of electromagnetic radiation - a photon, which is also a material body, but at the same time an electromagnetic wave, cannot escape back. Thus, not yet knowing about photons, the great Laplace once defined a black hole, then in 1916 it was predicted by the German physicist Schwarzschild, although the term “black hole” was proposed only in 1967.
Well, you never know, a supermassive body that sucks in everything that is inadvertently nearby - what is so special about our cosmos, which surpasses all imagination? There is something special - it was introduced by Einstein, however, not himself, but with the help of his theory of relativity. According to this theory, anything that falls into a black hole falls into a mathematical point. The hole is completely empty, except for the very point. And at that point, a completely impossible is observed - the so-called singularity: division by zero, infinite density, and from here the most fantastic consequences follow. For example, penetration into a parallel universe or instantaneous movement to another point in our space.
But it is somehow unusual for our world from the point of view of physics to have division by zero, it was always somehow confusing. Like it can only be in mathematics, but in reality - never.
In 1976, the famous British theoretical physicist Stephen Hawking discovered the quantum effect, thanks to which a black hole, that is, a body whose gravity, by definition, cannot release light outside, still emits it. He showed that if there is a pair "particle-antiparticle", connected to each other quantum-mechanically, and one of these particles falls into a hole, then the remaining free can pull it out from there. Now Cleveland theorists seem to have proven that the resulting evaporation of a black hole is so intense that it will evaporate before it even has time to form.
How they did it and how right they are in their conclusions, let's not guess, let's leave it to their colleagues to judge. But in reality, doubts about the existence of black holes have been expressed for a long time, and from time to time there are publications, the authors of which prove that there are no black holes. Despite the fact that several hundred have already been opened by now. “But these are not black holes,” the Cleveland theorists say. "They're just supermassive space objects."
Corresponding Member of the Russian Academy of Sciences Anatoly Cherepashchuk, Director of the State Astronomical Institute named after Sternberg Moscow State University MV Lomonosov, I am cautious about this in the comments.
“Indeed,” he said in an interview with an NG correspondent, “there is some terminological confusion here. We see objects in the sky that behave exactly as black holes should behave, and we believe they are black holes, and we call them that, but it remains to be shown that these are objects that have no surface. But there are many indirect indications that they just do not have a surface. "
Cherepashchuk sees nothing new in the fact that black holes evaporate: “They all evaporate. If the mass of a black hole does not exceed the mass of an average mountain, such as, for example, the Lenin Hills in Moscow, that is, 1015 grams, then it will really evaporate in one moment, by an explosion; whereas holes with a mass of several Suns would take thousands of cosmological times to completely evaporate. There are, however, exotic theories that take into account the fact that our space has not 4 dimensions, but 11, and according to these additional dimensions, the black hole also evaporates. And, therefore, the evaporation process is much faster than in ordinary four-dimensional space. In a sense, the work you are talking about is like a logical continuation of these theories. But, I repeat, there is a lot of indirect evidence that black holes do exist. "
Black holes are areas of dense matter in space that have such a strong attraction that no objects caught in the gravitational field of a black hole can leave it. Even the light that passes by is attracted by black holes. What science thinks about the existence of black holes will be discussed in our article.
Black holes are areas of dense matter in space that have such a strong attraction that no objects caught in the gravitational field of a black hole can leave it. Even the light that passes by is attracted by black holes. What science thinks about the existence of black holes will be discussed in our article.
The boundaries of black holes are called the "event horizon", and its magnitude is called the "gravitational radius".
Black holes, like many other physical phenomena, were initially discovered only in theory. The possibility of their existence follows from some of Einstein's equations, they converge with the theory of gravity (but it is not known how correct it is), which, again theoretically, confirms their existence.
In our time, the possibility of the formation of black holes is confirmed by the experimentally verified general theory of relativity (GTR). New data regularly appear, which are analyzed and interpreted within the framework of the above theory, which confirms the existence of some astronomical objects that partially coincide with the signs of black holes with a mass of 105-1010 solar masses. Therefore, it is impossible to prepare for the one hundred percent existence of black holes.
Today, there are 2 realistic and 2 hypothetical options for creating black holes: the catastrophically rapid compression of a massive star or the center of a part of the galaxy; and, accordingly, the creation of black holes as a consequence of the Big Bang and the emergence of high energies in nuclear reactions.
There are objects that are called black holes simply because of the correspondence of some of their properties with black holes, for example, stars, which are in the final stages of gravitational collapse. Modern astrophysics does not attach much importance to this difference, since the observed manifestations of an "almost collapsed" star and theoretically a "real" black hole are practically identical.
Black holes are not permanent. At first glance, it seems that these objects only draw in everything around them, but according to the quantum theory of gravitation, a black hole, absorbing, must continuously radiate, while losing its energy. The more "energy-mass" is lost, the higher the temperature and speed of radiation, which ultimately leads to an explosion. It is not known what remains from the black hole or not, but the answer to this question will be given by the quantum theory of gravity, on which they are going to work hard in the next couple of decades.
Three theories of the existence of black holes
There are three interesting theories about the existence of black holes:
There are a finite number of black holes in the Universe, they are in every galaxy, therefore, they can be a way to move in space, a kind of teleport - entered this black hole, left another. Moreover, you can "regulate" not only the place where you get to, but also the time.
According to Hugh Everett's theory of the plurality of worlds, the number of universes is infinite. Thanks to this, a hypothesis appeared that black holes are a passage to another universe. Physical laws in all Universes may differ, but only the checkpoints - black holes - are unshakable, though not eternal.
Black holes absorb everything in the gravitational field. If a person falls on a black hole - an internal observer, and someone looks at him - an external observer, then in theory the following situation can happen: a person falling on a black hole will see how time slows down for him and stops for eternity, and “ ambient "time, according to the theory of the English mathematician and theoretical physicist Penrose, the time of the development of the Universe is increasing at such a rate that he, the inner observer, has time to see the collapse of our space, and all existing realities, and all objects that once came across into a black hole. From the point of view of an external observer, the inner one will fly up to the black hole and stop, as if waiting for something. The universe, according to the theory, does not allow the existence of internal and external observers at the same time. After a minute of subjective time of a person who has jumped onto a black hole, but after billions of years from the point of view of an external observer, the falling person will be surprised to see how his very aged “external” friends begin to fall into his hole, and his “native” black hole will begin to merge with everyone other black holes ... Consequently, all external observers will simultaneously become internal, and now they are all flying together towards the Collapse of the Universe.
Taking into account the above facts of the existence of black holes, there are those who refute them. Physics professor Laura Marsini-Houghton of North Carolina argues that black holes simply cannot exist. She argues this by the fact that there is no direct evidence of their existence, and indirect evidence may be erroneous. However, so far this is only a theory.
At this stage of development, science is not able to either confirm or deny the existence of black holes. It remains to wait for new observations, their analysis and some subsequent answers to these questions.
The Hubble Space Telescope, perhaps for the first time, has provided clear evidence of the existence of black holes. He observed the disappearance of matter falling into the zone of action of a black hole, beyond the so-called "event horizon".
The observed faint light pulses of hot gas streams in the ultraviolet spectrum were discolored and then disappeared, forming a vortex around a massive, compact object named Cygnus XR-1. This mechanism of falling, similar, for example, to the fall of water at the edge of a waterfall, corresponds to a clear analogy with theoretical calculations of the fall of matter into a black hole.
The event horizon is a region of space surrounding a black hole, once in which, matter will never be able to leave this region and fall into the black hole. Light can still overcome the enormous force of gravity and send the last streams from the disappearing matter, but only for a short period of time, until the falling matter falls into the so-called singularity zone, beyond which even light can no longer go.
According to well-known theories, no other astronomical object other than a black hole can have an event horizon zone.
Black holes were identified by observing patterns of suction (overflow) of stellar gas masses in them. By estimating how much mass goes into a tiny region of space, you can determine how much space a black hole takes up and its mass.
Until now, no one has ever seen matter that has already fallen into the zone of the event horizon, falling into a black hole. Usually, a picture of a simple overflow of matter from a star adjacent to a black hole was observed. At the same time, the black hole was completely spherically enveloped by the mass of the flowing gas and itself resembled a small star in appearance, but emitting light in a spectrum close to ultraviolet or neutrons.
This secret has been hidden from the public for a long time. Scientists have meticulously analyzed and verified this data.
Hubble himself, of course, did not see the zone of the event horizon - this is too small a region of space at such a distance to be estimated. Hubble measured chaotic fluctuations in the ultraviolet light of boiling gas trapped in the gravitational zone of a black hole. Hubble caught the unique moments of a "fading train of pulses" that waned very quickly.
This mechanism is consistent with the generally accepted theory predicted by scientists: when matter falls close to the event horizon, the light from it quickly dims, because the closer to the center of the black hole, the stronger the gravitational force and the longer the waves become, gradually passing from the ultraviolet spectrum to neutron, and then disappear altogether. This effect is called "redshift".
The observed fragment of the falling material disappeared from the field of view of the Hubble telescope before it actually reached the event horizon. High-speed Hubble photometer sampled light pulses at a rate of 100,000 measurements per second. Hubble's ultraviolet resolution made it possible to see faint flickering of falling material within 1000 miles of the event horizon.
Dynamic models have previously predicted that Cygnus XR-1 "s belongs to a black hole. Gas cannot directly fall into it, like into a ditch, but forms a vortex in the form of a smoothed spiral disk.
Yes, there are. Black hole called a region of space-time in which the gravitational field is so strong that even light cannot leave this region. This happens if the size of the body is less than its gravitational radius rg.
What it is?
Black holes must arise from a very strong mass compression, while the gravitational field increases so strongly that it does not emit light or any other radiation. To overcome gravity and escape from the black hole, it would take second space velocity- more light. But, according to the theory of relativity, no body can develop a speed greater than the speed of light. Therefore, nothing can fly out of a black hole. Information cannot come from there either. It is impossible to know what happened to the one who fell into the black hole. Already near the holes, the properties of space and time change dramatically.
The theoretical possibility of the existence of such regions of space-time follows from some exact solutions of the Einstein equations. Simply put, Einstein predicted amazing properties of black holes, of which the most important is the presence of an event horizon in the black hole. According to the latest observational data, black holes do exist and have amazing properties. The existence of black holes follows from the theory of gravity: if this theory is correct, then the existence of black holes is true. Therefore, statements about direct evidence of the existence of black holes should be understood in the sense of confirming the existence of astronomical objects, so dense and massive, as well as having some other observable properties that they can be interpreted as black holes of general relativity. In addition, black holes are often called objects that do not strictly correspond to the above definition, but only those approaching in their properties to such a black hole - for example, they can be collapsing stars in the late stages of collapse.
Non-rotating black hole
For a non-rotating black hole, the radius of the event horizon coincides with the gravitational radius. At the event horizon for an outside observer, the passage of time stops. A spacecraft sent to a black hole, from the point of view of a distant observer, will never cross the event horizon, but will continuously slow down as it approaches it. Everything that happens under the event horizon, inside the black hole, cannot be seen by an external observer. An astronaut in his spacecraft is, in principle, capable of penetrating the event horizon, but he will not be able to convey any information to an external observer. At the same time, an astronaut freely falling under the event horizon will probably see another universe and even his own future. This is due to the fact that inside the black hole the spatial and temporal coordinates change places, and travel in space is here replaced by travel in time.
Spinning black hole
Its properties are even more amazing. Their event horizon has a smaller radius, it is immersed in the ergosphere - a region of space-time in which bodies must continuously move, picked up by the vortex gravitational field of a rotating black hole.
These unusual properties of black holes seem simply fantastic, so their existence in nature is often questioned.
A black hole in a binary star system
In this case, the effects of the black hole are most pronounced, since in a binary star system, one star is a bright giant, and the other is a black hole. Gas from the shell of the giant star flows out to the black hole, swirls around it, forming a disk. Layers of gas in the disk in spiral orbits approach the black hole and fall into it. But before falling at the edge of the black hole, the gas heats up as a result of friction to a huge temperature of millions of degrees and emits in the X-ray range. From this X-ray emission, black holes are found in binary stellar systems.
Conclusion
Massive black holes are thought to arise at the centers of compact star clusters. Perhaps the X-ray source in the constellation Cygnus, Cygnus-X-1, is such a black hole.
Astronomers do not exclude that in the past, black holes could arise at the beginning of the expansion of the Universe, so the formation of very small black holes is possible.
The values of the masses of a large number of neutron stars and black holes confirm the validity of the predictions of A. Einstein's theory of relativity. In recent years, the problem of the hypothesis of black holes in the Universe has become an observational reality. This means a qualitatively new stage in the study of black holes and their amazing properties, there is hope for new discoveries in this area.