How to find the average weight of a black hole. Dimensions and mass of black holes - video visualization

Black holes in the universe

A black hole is a space object that is formed during unlimited gravitational compression (gravitational collapse) of massive space bodies. The existence of these objects is predicted by the general theory of relativity. The term "black hole" itself was introduced into science by the American physicist John Wheeler in 1968 to designate a collapsed star.

A black hole is a region in space that has arisen as a result of a complete gravitational collapse of matter, in which the gravitational attraction is so great that neither matter, nor light, nor other information carriers can leave it. Therefore, the interior of a black hole is causally unrelated to the rest of the universe; physical processes occurring inside a black hole cannot affect 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 it. This surface is called the "event horizon". Since so far there are only indirect indications of the existence of black holes at distances of thousands of light years from the Earth, our further presentation is based mainly on theoretical results.

Astronomers have come to the conclusion that black holes are not born huge, but gradually grow due to the gas and stars of galaxies. The data show that giant black holes did not precede the birth of galaxies, but evolved along with them, absorbing a certain percentage of the mass of stars and gas from the central region of the galaxy. This means that in smaller galaxies, black holes are less massive, their masses are not much more than a few million solar masses. Black holes at the centers of giant galaxies include billions of solar masses. The thing is that the final mass of a black hole is formed in the process of galaxy formation. In some cases, black holes increase not only by absorbing the gas of a single galaxy, but also by merging galaxies, as a result of which their black holes merge.

Formation of black holes

Black holes are formed as a result of the collapse of giant neutron stars with a mass of more than 3 solar masses. When compressed, their gravitational field is condensed more and more. Finally, the star shrinks to such an extent that light can no longer overcome its attraction. The radius to which a star must shrink in order to turn into a black hole is called the gravitational radius. For massive stars, it is several tens of kilometers. Since black holes do not shine, the only way to judge them is to observe the effect of their gravitational field on other bodies. There is indirect evidence for the existence of black holes in more than 10 close double X-ray stars. This is supported, firstly, by the absence of known manifestations of a solid surface characteristic of an X-ray pulsar or X-ray burster, and, secondly, by the large mass of the invisible component of the binary system (more than 3 solar masses). One of the most likely black hole candidates is Cygnus X-1, the brightest X-ray source in the constellation Cygnus.

According to modern ideas, there are four scenarios of education black hole:

1. Gravitational collapse (catastrophic compression) of a fairly massive star (more than 3.6 solar masses) at the final stage of its evolution.

2. Collapse of the central part of the galaxy or pragalactic gas. Modern views place a huge black hole at the center of many, if not all, spiral and elliptical galaxies. For example, in the center of our 3. 3. 3. Galaxy there is a black hole Sagittarius A * with a mass of 4.31x10 6 M, around which a smaller black hole rotates.

4. Formation of black holes at the moment of the Big Bang as a result of fluctuations of the gravitational field and/or matter. Such black holes are called primordial.

Evolution of black holes

Scientists have strong evidence for the existence of two different classes of black holes: the first are black holes with stellar masses about 10 times that of the Sun, the second are supermassive black holes that are located in the center of galaxies and have masses from hundreds of thousands to billions of solar masses. But it remains a mystery how medium-mass black holes form and exist? These are so-called black holes with intermediate masses between 100 and 10,000 solar masses.

Evidence for the origin of these objects remains controversial. So far, more than one such black hole has not been found in a single galaxy. But a team of researchers found two medium-mass black holes in the M82 galaxy, which is about 12 million light-years from Earth, as a result of studying X-ray data.

According to the characteristics of the radiation emitted by black holes in M82, the researchers concluded that the mass of one of the black holes ranges from 12 to 43 thousand solar masses, and the mass of the second - from 200 to 800 solar masses. The first object is located at a distance of 290 light years from the center of the galaxy M82. The second object is located at a distance of 600 light years in projection from the center of the galaxy.

“For the first time, two medium-mass black holes have been discovered in the same galaxy,” said one of the researchers Hua Feng from Tsinghua University, China. “Their location near the center of the galaxy may contain information about the origin of the largest black holes in the universe, such as supermassive black holes, found at the centers of most galaxies."

One possible mechanism for the formation of supermassive black holes is a chain reaction of collisions of stars and compact star clusters, which leads to the accumulation of very massive objects, which then form into intermediate-mass black holes. Further, the intermediate black holes are attracted to the center of the galaxy and merge with the supermassive black hole at the center of the galaxy.

"We can't say for sure whether a similar black hole formation process in M82 is a confirmation of this theory, but we do know that both of these medium-sized black holes are located near star clusters," said Phil Caret of Iowa State University, one of the authors of the paper. “In addition, M82 is the closest galaxy to us, where conditions are similar to those in the early Universe, with a large number of stars.”

Until now, astronomers did not know for sure whether two medium-mass black holes could be present in the same galaxy at once. Perhaps the discovery will shed light on the formation and evolution of supermassive black holes in galaxies.

Types of black holes

Black holes of stellar masses. Stellar-mass black holes are formed as the final stage of the life of a star, after the complete burnout of thermonuclear fuel and the termination of the reaction, the star should theoretically begin to cool, which will lead to a decrease in internal pressure and compression of the star under the influence of gravity. Compression can stop at a certain stage, or it can turn into a rapid gravitational collapse. Depending on the star's mass and torque, the following final states are possible:

An extinguished very dense star, consisting mainly, depending on the mass, of helium, carbon, oxygen, neon, magnesium, silicon or iron (the main elements are listed in order of increasing mass of the remnant of the star). Such remnants are called white dwarfs, their mass is limited from above by the Chandrasekhar limit.

A neutron star whose mass is limited by the Oppenheimer-Volkov limit.

Black hole.

As the mass of the remnant of the star increases, the equilibrium configuration moves down the sequence described. The rotational moment increases the limiting masses at each stage, but not qualitatively, but quantitatively (by a maximum of 2-3 times).

The conditions (mainly mass) under which the final state of the evolution of a star is a black hole have not been studied well enough, since for this it is necessary to know the behavior and states of matter at extremely high densities inaccessible to experimental study. Additional difficulties are presented by modeling stars at the later stages of their evolution due to the complexity of the emerging chemical composition and a sharp decrease in the characteristic time of the processes. Suffice it to mention that one of the largest cosmic catastrophes, supernova explosions, occurs precisely at these stages of stellar evolution. Various models give a lower estimate of the mass of a black hole resulting from gravitational collapse, from 2.5 to 5.6 solar masses. The radius of a black hole is very small - a few tens of kilometers.

Subsequently, a black hole can grow due to the absorption of matter - as a rule, this is the gas of a neighboring star in binary star systems (a collision of a black hole with any other astronomical object is very unlikely due to its small diameter). The process of gas falling onto any compact astrophysical object, including a black hole, is called accretion. At the same time, due to the rotation of the gas, an accretion disk is formed, in which the matter accelerates to relativistic velocities, heats up and, as a result, strongly radiates, including in the X-ray range, which makes it possible in principle to detect such accretion disks (and, therefore, black holes) using ultraviolet X-ray telescopes. The main problem is the small size and difficulty of detecting the differences between the accretion disks of neutron stars and black holes, which leads to uncertainty in identifying astronomical objects with black holes. The main difference is that gas falling on all objects sooner or later encounters a solid surface, which leads to intense radiation during deceleration, but a cloud of gas falling on a black hole, due to the infinitely growing gravitational time dilation (redshift) it simply fades rapidly as it approaches the event horizon, which was observed by the Hubble telescope in the case of the Cygnus X-1 source.

The collision of black holes with other stars, as well as the collision of neutron stars, causing the formation of a black hole, leads to the most powerful gravitational radiation, which, as expected, can be detected in the coming years with the help of gravitational telescopes. Currently, there are reports of collisions in the X-ray range. On August 25, 2011, a message appeared that for the first time in the history of science, a group of Japanese and American specialists was able in March 2011 to record the moment of the death of a star that is absorbed by a black hole.

Supermassive black holes. Expanded very massive black holes, according to modern concepts, form the core of most galaxies. These include the massive black hole at the core of our galaxy - Sagittarius A

At present, the existence of black holes of stellar and galactic scales is considered by most scientists to be reliably proven by astronomical observations.

American astronomers have found that the masses of supermassive black holes can be significantly underestimated. The researchers found that in order for the stars to move in the M87 galaxy (which is located at a distance of 50 million light years from Earth) as it is observed now, the mass of the central black hole must be at least 6.4 billion solar masses, that is, in twice the current estimate of the M87 core, which is 3 billion solar masses.

For a black hole in the nucleus of a galaxy, the gravitational radius is 3 10 15 cm = 200 AU. That is, five times the distance from the Sun to Pluto. The critical density in this case is equal to 0.2 10 -3 g/cm³, which is several times less than the density of air.

Primordial black holes currently have the status of a hypothesis. If at the initial moments of the life of the Universe there were sufficient deviations from the homogeneity of the gravitational field and the density of matter, then black holes could form from them by means of collapse. At the same time, their mass is not limited from below, as in stellar collapse - their mass could probably be quite small. The detection of primordial black holes is of particular interest in connection with the possibility of studying the phenomenon of black hole evaporation.

Quantum black holes. It is assumed that stable microscopic black holes, the so-called quantum black holes, can appear as a result of nuclear reactions. For a mathematical description of such objects, it is necessary quantum theory gravity. However, from general considerations, it is very likely that the mass spectrum of black holes is discrete and there is a minimal black hole - the Planck black hole. Its mass is about 10 −5 g, its radius is 10 −35 m. The Compton wavelength of a Planck black hole is equal in order of magnitude to its gravitational radius.

Even if quantum black holes exist, their lifetime is extremely short, making their direct detection very problematic.

Recently, experiments have been proposed to find evidence of the appearance of black holes in nuclear reactions. However, for the direct synthesis of a black hole in an accelerator, an energy of 10 26 eV, unattainable today, is required. Apparently, virtual intermediate black holes can appear in superhigh-energy reactions.

Experiments on proton-proton collisions with a total energy of 7 TeV at the Large Hadron Collider have shown that this energy is not enough to form microscopic black holes. Based on these data, it is concluded that microscopic black holes must be heavier than 3.5–4.5 TeV, depending on the specific implementation.

A black hole is an astronomical region in space and time, within which gravitational attraction tends to infinity. To leave a black hole, objects must reach speeds much faster than the speed of light. And since this is impossible, even the quanta of the light itself are not emitted from the region of the black hole. From all this it follows that the region of the black hole is absolutely invisible to the observer, no matter how far away from him it is. Therefore, it is possible to detect and determine the size and mass of black holes only by analyzing the environment and behavior of objects located near them.

At the 20th Relativistic Astrophysics Symposium in Texas in 2001, astronomers Carl Gebhardt and John Kormendy took practical measurements of the masses of nearby black holes, giving astronomers insight into black hole growth. With this method, there were 19 new black holes in addition to the 19 already known at the time. All of them are supermassive and have a weight of one to a billion solar masses. They are located at the centers of galaxies.

The mass measurement method is based on the observation of the movement of stars and gas near the centers of their galaxies. Such measurements can only be carried out at the high spatial resolution that space telescopes such as Hubble or NuSTAR can provide. The essence of the method is to analyze the variability of quasars and the circulation of huge gas around the hole. The brightness of the radiation of rotating gas clouds directly depends on the energy of the X-ray radiation of the black hole. Since light has a strictly defined speed, changes in the brightness of the gas clouds are visible to the observer later than the change in the brightness of the central source of radiation. The distance from the gas clouds to the center of the black hole is calculated from the time difference. Together with the speed of rotation of gas clouds, the mass of the black hole is also calculated. However, this method involves uncertainty, since there is no way to check the correctness of the final result. On the other hand, the data obtained by this method correspond to the relationship between the masses of black holes and the masses of galaxies.

The classical way to measure the mass of a black hole, proposed by Einstein's contemporary Schwarzschild, is described by the formula M=r*c^2/2G, where r is the gravitational radius of the black hole, c is the speed of light, and G is the gravitational constant. However, this one accurately describes the mass of an isolated, non-rotating, uncharged, and non-evaporating black hole.

At all new way determination of the masses of black holes, which made it possible to discover and study black holes of the "average". It is based on the radio interference analysis of jets - matter ejections formed during the absorption of mass by a black hole from the disk surrounding it. The speed of the jets can be over half the speed of light. And since the mass accelerated to such speeds emits X-rays, it can be registered by a radio interferometer. The method of mathematical modeling of such jets makes it possible to obtain more exact values average masses of black holes.

American and Australian astrophysicists have discovered a candidate for intermediate-mass black holes. They got this name because they are heavier than ordinary objects - that is, objects formed as a result of the gravitational collapse of stars, but lighter than supermassive black holes, usually located in the active nuclei of large galaxies. The origin of unusual objects is still unclear. Below we will talk about black holes of intermediate masses and about the discovery of scientists.

Most of the black holes known to scientists - that is, objects that no matter can leave (ignoring quantum effects) - are either stellar-mass black holes or supermassive black holes.

The origin of these gravitational objects is approximately clear to astronomers. The former, as is clear from their name, represent the final stage in the evolution of heavy luminaries, when thermonuclear reactions cease in their depths. They are so heavy that they do not turn into either white dwarfs or neutron stars.

Small stars like the Sun turn into white dwarfs. Their force of gravitational compression is balanced by the electromagnetic repulsion of the electron-nuclear plasma. In heavier stars, gravity is restrained by the pressure of nuclear matter, resulting in the formation of neutron stars. The core of such objects is formed by a neutron liquid, which is covered by a thin plasma layer of electrons and heavy nuclei. Finally, the heaviest luminaries turn into black holes, which is perfectly described by general relativity and statistical physics.

The limiting value of the mass of a white dwarf, which prevents it from turning into a neutron star, was estimated in 1932 by the Indian astrophysicist Subramanyan Chandrasekhar. This parameter is calculated from the equilibrium condition for the degenerate electron gas and gravitational forces. Modern meaning the Chandrasekhar limit is estimated at about 1.4 solar masses. The upper limit on the mass of a neutron star, at which it does not turn into a black hole, is called the Oppenheimer-Volkov limit. It is determined from the equilibrium condition for the degenerate neutron gas pressure and gravitational forces. In 1939, scientists calculated its value at 0.7 solar masses; modern estimates range from 1.5 to 3.0.

The most massive stars are 200-300 times heavier than the Sun. As a rule, the mass of a black hole that originated from a star does not exceed this order. At the other end of the scale are supermassive black holes - hundreds of thousands or even tens of billions of times heavier than the Sun. Typically, such monsters are located in the active centers of large galaxies and have a decisive influence on them. Despite the fact that the origin of supermassive black holes also raises many questions, by now enough such objects (more strictly, candidates for them) have been discovered so as not to doubt their existence.

For example, in the center Milky Way, at a distance of 7.86 kiloparsecs from the Earth, is the heaviest object in the Galaxy - the supermassive black hole Sagittarius A *, which is more than four million times heavier than the Sun. The nearby large star system, the Andromeda Nebula, hosts an even heavier object: a supermassive black hole that is probably 140 million times heavier than the Sun. Astronomers estimate that in about four billion years, a supermassive black hole from the Andromeda Nebula will swallow one from the Milky Way.

This mechanism indicates the most probable way the formation of giant black holes - they simply absorb all the matter around them. However, the question remains: do black holes of intermediate masses exist in nature - between stellar and superheavy ones? Observations recent years, including one published in a recent issue of the journal Nature, confirm this. In the publication, the authors reported the discovery in the center of the globular star cluster 47 Tucanae (NGC 104) of a likely candidate for intermediate-mass black holes. As estimates show, it is heavier than the Sun by about 2.2 thousand times.

The 47 Tucanae cluster is located 13,000 light-years from Earth in the constellation Tucanae. This set of gravitationally bound luminaries is distinguished by its great age (12 billion years) and extremely high brightness among similar objects (second only to Omega Centauri). NGC 104 contains thousands of stars bounded by a conventional sphere with a diameter of 120 light years (this is three orders of magnitude smaller than the diameter of the Milky Way disk). Also in 47 Tucana there are about twenty pulsars - it was they who became the main object of research by scientists.

Previous searches at the center of NGC 104 for a black hole have been unsuccessful. Such objects reveal themselves indirectly, by the characteristic X-ray emission coming from the accretion disk around them, formed by heated gas. Meanwhile, the center of NGC 104 contains almost no gas. On the other hand, a black hole can be detected by its effect on the stars rotating in its vicinity - something like this one can study Sagittarius A *. However, here, too, a problem lay in wait for scientists - the center of NGC 104 contains too many stars to make sense of their individual movements.

Scientists have tried to get around both difficulties, while at the same time not abandoning the usual methods of detecting black holes. First, astronomers analyzed the dynamics of the stars of the entire globular cluster as a whole, and not just those stars that are close to its center. To do this, the authors took data on the dynamics of the luminaries of 47 Tucanas, collected in the course of observations by the Australian Parkes Radio Observatory. The scientists used the obtained information for computer simulation within the N-body gravitational problem. It showed that there is something at the center of NGC 104 that, in its characteristics, resembles an intermediate-mass black hole. However, this was not enough.

The researchers decided to test their conclusions on pulsars - the compact remnants of dead stars, the radio signals of which astronomers have learned to track quite well. If there is an intermediate-mass black hole in NGC 104, then the pulsars cannot be located too close to the center of 47 Tucana - and vice versa. As the authors expected, the first scenario was confirmed: the location of the pulsars in NGC 104 correlates well with the fact that there is an intermediate-mass black hole in the center of the cluster.

The authors believe that this kind of gravitational objects can also be located in the centers of other globular clusters - probably, where they are already or not yet searched for. This will require careful consideration of each of these clusters. What role do intermediate-mass black holes play and how did they arise? While this is not known for sure. Despite the many options for their further evolution, study co-author Bulent Kiziltan believes that "they may be the original seeds that grew into the monsters that we see today in the centers of galaxies."

Intermediate-mass black holes in the cores of galaxies

An average-mass black hole weighs about ten thousand suns. This is ten thousand times less than the mass of Gargantua, but a thousand times more than the weight of ordinary black holes - just what Cooper needs for maneuvers.

Medium-mass holes are sometimes thought to form at the center of dense clusters of stars called globular star clusters. And some of them with no small degree of probability fall into the core of galaxies, where giant black holes are located.

Take, for example, the Andromeda galaxy, the closest large galaxy to our own (Figure 7.4), in whose core lies a Gargantua-sized black hole with a mass of 100 million Suns. To such gigantic black holes is drawn great amount stars - up to a thousand stars per cubic light year. When an intermediate-mass hole passes through such a saturated region, it shifts the stars with its gravity, leaving a trail of increased stellar density in its wake. This wake, in turn, attracts a medium-mass hole, slowing down its movement; this process is called dynamic friction. As the IMA slows down, it is pulled closer to the giant black hole. In this way, nature (in the Kip version) can “supply” Cooper with the medium-mass black hole needed for his gravitational maneuvers.

Rice. 7.4. Left: The Andromeda galaxy, with a Gargantua-sized black hole lurking at its core. Right: Dynamic friction that causes an intermediate-mass hole to gradually slow down and be pulled closer and closer to the giant black hole.