Black hole as it is also called. Evaporation of black holes

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”.

Nowadays. 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; observations of 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 hole's enormous gravitational force 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 perturbation.

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.

Black holes are perhaps the most mysterious and enigmatic astronomical objects in our Universe; since 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 most likely will 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 to date 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

A star can turn into a black hole towards the end of its life. During this transformation, the star contracts very strongly, while its mass is maintained. The star turns into a small but very heavy ball. If we assume that our planet Earth will become a black hole, then its diameter in this state will be only 9 millimeters. But the Earth will not be able to turn into a black hole, because completely different reactions take place in the core of planets, not the same as in stars.

Such a strong compression and compaction of the star occurs because, under the influence of thermonuclear reactions in the center of the star, its attractive force increases greatly and begins to attract the surface of the star to its center. Gradually, the speed at which the star contracts increases and eventually begins to exceed the speed of light. When a star reaches this state, it stops glowing because the particles of light - quanta - cannot overcome the force of gravity. A star in this state stops emitting light; it remains “inside” the gravitational radius - the boundary within which all objects are attracted to the surface of the star. Astronomers call this boundary the event horizon. And beyond this boundary, the gravitational force of the black hole decreases. Since light particles cannot overcome the gravitational boundary of a star, a black hole can only be detected using instruments, for example, if for unknown reasons a spaceship or another body - a comet or an asteroid - begins to change its trajectory, it means that it most likely came under the influence of the gravitational forces of a black hole . A controlled space object in such a situation must urgently turn on all engines and leave the zone of dangerous gravity, and if there is not enough power, then it will inevitably be swallowed up by a black hole.

If the Sun could turn into a black hole, then the planets of the solar system would be within the gravitational radius of the Sun and it would attract and absorb them. Fortunately for us, this will not happen, because... Only very large, massive stars can turn into a black hole. The sun is too small for this. During its evolution, the Sun will most likely become an extinct black dwarf. Other black holes that already exist in space are not dangerous for our planet and terrestrial spaceships - they are too far from us.

In the popular TV series "The Big Bang Theory", which you can watch, you will not learn the secrets of the creation of the Universe or the reasons for the emergence of black holes in space. The main characters are passionate about science and work at the physics department at the university. They constantly find themselves in various ridiculous situations, which are fun to watch.

There is no cosmic phenomenon more mesmerizing in its beauty than black holes. As you know, the object got its name due to the fact that it is able to absorb light, but cannot reflect it. Due to their enormous gravity, black holes suck in everything that is near them - planets, stars, space debris. However, this is not all there is to know about black holes, as there are many amazing facts about them.

Black holes have no point of no return

For a long time it was believed that everything that falls into the region of a black hole remains in it, but the result of recent research is that after a while the black hole “spits out” all its contents into space, but in a different form, different from the original one. The event horizon, which was considered the point of no return for space objects, turned out to be only their temporary refuge, but this process occurs very slowly.

The Earth is threatened by a black hole

The solar system is only part of an infinite galaxy, which contains a huge number of black holes. It turns out that the Earth is threatened by two of them, but fortunately, they are located at a great distance - about 1600 light years. They were discovered in a galaxy that was formed as a result of the merger of two galaxies.


Scientists saw black holes only because they were near the solar system using an X-ray telescope, which is capable of capturing X-rays emitted by these space objects. Black holes, since they are located next to each other and practically merge into one, were called by one name - Chandra in honor of the Moon God from Hindu mythology. Scientists are confident that Chandra will soon become one due to the enormous force of gravity.

Black holes may disappear over time

Sooner or later, all the contents come out of the black hole and only radiation remains. As black holes lose mass, they become smaller over time and then disappear completely. The death of a space object is very slow and therefore it is unlikely that any scientist will be able to see how the black hole decreases and then disappears. Stephen Hawking argued that the hole in space is a highly compressed planet and over time it evaporates, starting at the edges of the distortion.

Black holes may not necessarily look black

Black holes are not created out of nowhere; they are based on an extinct star.

Stars glow in space thanks to their supply of thermonuclear fuel. When it ends, the star begins to cool, gradually turning from a white dwarf to a black dwarf. The pressure inside the cooled star begins to decrease. Under the influence of gravity, the cosmic body begins to shrink. The consequence of this process is that the star seems to explode, all its particles scatter in space, but at the same time the gravitational forces continue to act, attracting neighboring space objects, which are then absorbed by it, increasing the power of the black hole and its size.

Supermassive black hole

A black hole, tens of thousands of times larger than the size of the Sun, is located in the very center of the Milky Way. Scientists called it Sagittarius and it is located at a distance from the Earth 26,000 light years. This region of the galaxy is extremely active and is rapidly absorbing everything that is near it. She also often “spits out” extinct stars.


What is surprising is the fact that the average density of a black hole, even considering its enormous size, can even be equal to the density of air. As the radius of a black hole increases, that is, the number of objects captured by it, the density of the black hole becomes smaller and this is explained by the simple laws of physics. So the largest bodies in space may actually be as light as air.

Black hole can create new universes

No matter how strange it may sound, especially given the fact that in fact black holes absorb and accordingly destroy everything around them, scientists are seriously thinking that these space objects could mark the beginning of the emergence of a new Universe. So, as we know, black holes not only absorb matter, but can also release it at certain periods. Any particle that comes out of a black hole can explode and this will become a new Big Bang, and according to his theory, our Universe appeared this way, therefore it is possible that the Solar system that exists today and in which the Earth revolves, populated by a huge number of people, was once born from a massive black hole.

Time passes very slowly near a black hole

When an object comes close to a black hole, no matter how much mass it has, its motion begins to slow down and this happens because in the black hole itself, time slows down and everything happens very slowly. This is due to the enormous gravitational force that the black hole has. Moreover, what happens in the black hole itself happens quite quickly, so if an observer were looking at the black hole from the outside, it would seem to him that all the processes occurring in it were proceeding slowly, but if he fell into its funnel, the gravitational forces would instantly tore it apart.

Every person who gets acquainted with astronomy sooner or later experiences a strong curiosity about the most mysterious objects of the Universe - black holes. These are real lords of darkness, capable of “swallowing” any atom passing nearby and not allowing even light to escape - their attraction is so powerful. These objects pose a real challenge for physicists and astronomers. The former cannot yet understand what happens to the matter that has fallen inside the black hole, and the latter, although they explain the most energy-consuming phenomena in space by the existence of black holes, have never had the opportunity to observe any of them directly. We will tell you about these interesting celestial objects, find out what has already been discovered and what remains to be learned in order to lift the veil of secrecy.

What is a black hole?

The name “black hole” (in English - black hole) was proposed in 1967 by the American theoretical physicist John Archibald Wheeler (see photo on the left). It served to designate a celestial body, the attraction of which is so strong that even light does not let go of itself. That is why it is “black” because it does not emit light.

Indirect observations

This is the reason for such mystery: since black holes do not glow, we cannot see them directly and are forced to look for and study them using only indirect evidence that their existence leaves in the surrounding space. In other words, if a black hole engulfs a star, we cannot see the black hole, but we can observe the devastating effects of its powerful gravitational field.

Laplace's intuition

Although the expression “black hole” to denote the hypothetical final stage of the evolution of a star that has collapsed into itself under the influence of gravity is relatively recent, the idea of ​​the possibility of the existence of such bodies arose more than two centuries ago. The Englishman John Michell and the Frenchman Pierre-Simon de Laplace independently hypothesized the existence of “invisible stars”; at the same time, they were based on the usual laws of dynamics and Newton's law of universal gravitation. Today, black holes have received their correct description based on Einstein's general theory of relativity.

In his work “Exposition of the System of the World” (1796), Laplace wrote: “A bright star of the same density as the Earth, with a diameter 250 times greater than the diameter of the Sun, would, thanks to its gravitational attraction, prevent light rays from reaching us. Therefore, it is possible that the largest and brightest celestial bodies are invisible for this reason.”

Invincible gravity

Laplace's idea was based on the concept of escape velocity (second cosmic velocity). A black hole is such a dense object that its gravity can hold back even light, which develops the highest speed in nature (almost 300,000 km/s). In practice, escaping from a black hole requires speeds greater than the speed of light, but this is impossible!

This means that a star of this kind will be invisible, since even light will not be able to overcome its powerful gravity. Einstein explained this fact through the phenomenon of light bending under the influence of a gravitational field. In reality, near a black hole, space-time is so curved that the trajectories of light rays also close on themselves. In order to turn the Sun into a black hole, we will have to concentrate all of its mass in a ball with a radius of 3 km, and the Earth will have to turn into a ball with a radius of 9 mm!

Types of black holes

Just about ten years ago, observations suggested the existence of two types of black holes: stellar, whose mass is comparable to the mass of the Sun or slightly exceeds it, and supermassive, whose mass ranges from several hundred thousand to many millions of solar masses. However, relatively recently, X-ray images and high-resolution spectra obtained from artificial satellites such as Chandra and XMM-Newton brought to the fore a third type of black hole - with an average mass exceeding the mass of the Sun by thousands of times.

Stellar black holes

Stellar black holes became known earlier than others. They are formed when a large-mass star, at the end of its evolutionary path, exhausts its reserves of nuclear fuel and collapses into itself due to its own gravity. An explosion that shakes a star (a phenomenon known as a “supernova explosion”) has catastrophic consequences: if the star’s core is more than 10 times the mass of the Sun, no nuclear force can resist the gravitational collapse that will result in the creation of a black hole.

Supermassive black holes

Supermassive black holes, first noted in the nuclei of some active galaxies, have a different origin. There are several hypotheses regarding their birth: a stellar black hole, which over the course of millions of years devours all the stars around it; a cluster of black holes merging together; a colossal gas cloud collapsing directly into a black hole. These black holes are among the most energetic objects in space. They are located at the centers of many, if not all, galaxies. Our Galaxy also has such a black hole. Sometimes, due to the presence of such a black hole, the cores of these galaxies become very bright. Galaxies with black holes at the center, surrounded by large amounts of falling matter and therefore capable of producing colossal amounts of energy, are called "active" and their cores are called "active galactic nuclei" (AGN). For example, quasars (the most distant cosmic objects from us that are accessible to our observation) are active galaxies in which we see only a very bright core.

Medium and mini

Another mystery remains the medium-mass black holes, which, according to recent research, may be at the center of some globular clusters, such as M13 and NCC 6388. Many astronomers are skeptical about these objects, but some new research suggests the presence of black holes medium-sized even near the center of our Galaxy. English physicist Stephen Hawking also put forward a theoretical assumption about the existence of a fourth type of black hole - a “mini-hole” with a mass of only a billion tons (which is approximately equal to the mass of a large mountain). We are talking about primary objects, that is, those that appeared in the first moments of the life of the Universe, when the pressure was still very high. However, not a single trace of their existence has yet been discovered.

How to find a black hole

Just a few years ago, a light came on over black holes. Thanks to constantly improving instruments and technologies (both ground-based and space-based), these objects are becoming less and less mysterious; more precisely, the space surrounding them becomes less mysterious. In fact, since the black hole itself is invisible, we can only recognize it if it is surrounded by enough matter (stars and hot gas) orbiting around it at a short distance.

Watching binary systems

Some stellar black holes have been discovered by observing the orbital motion of a star around an unseen companion in a binary system. Close binary systems (that is, consisting of two stars very close to each other), in which one of the companions is invisible, are a favorite object of observation for astrophysicists searching for black holes.

An indication of the presence of a black hole (or neutron star) is the strong emission of X-rays caused by a complex mechanism that can be schematically described as follows. Thanks to its powerful gravity, a black hole can rip matter out of its companion star; this gas spreads out into a flat disk and spirals down into the black hole. Friction resulting from collisions between particles of falling gas heats the inner layers of the disk to several million degrees, which causes powerful X-ray radiation.

X-ray observations

X-ray observations of objects in our Galaxy and neighboring galaxies, carried out for several decades, have made it possible to detect compact binary sources, about a dozen of which are systems containing black hole candidates. The main problem is determining the mass of an invisible celestial body. The mass (although not very precise) can be found by studying the motion of the companion or, much more difficult, by measuring the intensity of the X-ray radiation of the falling material. This intensity is related by an equation to the mass of the body on which this substance falls.

Nobel laureate

Something similar can be said for supermassive black holes observed in the cores of many galaxies, the masses of which are estimated by measuring the orbital velocities of the gas falling into the black hole. In this case, caused by the powerful gravitational field of a very large object, a rapid increase in the speed of gas clouds orbiting in the center of galaxies is detected by observations in the radio range, as well as in optical rays. Observations in the X-ray range can confirm the increased release of energy caused by matter falling into the black hole. Research in X-rays was started in the early 1960s by the Italian Riccardo Giacconi, who worked in the USA. His Nobel Prize in 2002 recognized his "pioneering contributions to astrophysics leading to the discovery of X-ray sources in space."

Cygnus X-1: first candidate

Our Galaxy is not immune to the presence of candidate black hole objects. Fortunately, none of these objects are close enough to us to pose a threat to the existence of Earth or the solar system. Despite the large number of compact X-ray sources that have been identified (and these are the most likely candidates for black holes), we have no confidence that they actually contain black holes. The only one among these sources that does not have an alternative version is the close binary system Cygnus X-1, that is, the brightest source of X-ray radiation in the constellation Cygnus.

Massive stars

This system, whose orbital period is 5.6 days, consists of a very bright blue star of large size (its diameter is 20 times that of the Sun, and its mass is about 30 times larger), easily visible even in your telescope, and an invisible second star, the mass of which is estimated at several solar masses (up to 10). Located 6,500 light-years away, the second star would be perfectly visible if it were an ordinary star. Its invisibility, the powerful X-ray emission produced by the system and, finally, the mass estimate lead most astronomers to believe that this is the first confirmed discovery of a stellar black hole.

Doubts

However, there are also skeptics. Among them is one of the largest researchers of black holes, physicist Stephen Hawking. He even made a bet with his American colleague Keel Thorne, an ardent supporter of classifying the Cygnus X-1 object as a black hole.

The debate over the identity of the Cygnus X-1 object is not Hawking's only bet. Having devoted several nine years to theoretical studies of black holes, he became convinced of the fallacy of his previous ideas about these mysterious objects. In particular, Hawking assumed that matter, after falling into a black hole, disappears forever, and with it all of its information luggage disappears. He was so sure of this that he made a bet on this topic in 1997 with his American colleague John Preskill.

Admitting a mistake

On July 21, 2004, in his speech at the Congress on the Theory of Relativity in Dublin, Hawking admitted that Preskill was right. Black holes do not lead to the complete disappearance of matter. Moreover, they have a certain kind of “memory”. They may well contain traces of what they have consumed. Thus, by “evaporating” (that is, slowly emitting radiation due to the quantum effect), they can return this information to our Universe.

Black holes in the Galaxy

Astronomers still have many doubts about the presence of stellar black holes (like the one belonging to the binary system Cygnus X-1) in our Galaxy; but there is much less doubt about supermassive black holes.

In the center

Our Galaxy has at least one supermassive black hole. Its source, known as Sagittarius A*, is precisely localized in the center of the plane of the Milky Way. Its name is explained by the fact that it is the most powerful radio source in the constellation Sagittarius. It is in this direction that both the geometric and physical centers of our galactic system are located. Located about 26,000 light-years away, the supermassive black hole associated with radio wave source Sagittarius A* has a mass estimated at about 4 million solar masses, contained in a space the volume of which is comparable to the volume of the solar system. Its relative proximity to us (it is by far the closest supermassive black hole to Earth) has led to the object being studied particularly closely in recent years by the Chandra space observatory. It turned out, in particular, that it is also a powerful source of X-ray radiation (but not as powerful as sources in active galactic nuclei). Sagittarius A* may be a dormant remnant of what was the active core of our Galaxy millions or billions of years ago.

Second black hole?

However, some astronomers believe that there is another surprise in our Galaxy. We are talking about a second black hole of average mass, holding together a cluster of young stars and preventing them from falling into a supermassive black hole located in the center of the Galaxy itself. How can it be that at a distance of less than one light year from it there could be a star cluster that is barely 10 million years old, that is, by astronomical standards, very young? According to the researchers, the answer is that the cluster was not born there (the environment around the central black hole is too hostile for star formation), but was “pulled” there due to the existence of a second black hole inside it, which has an average mass.

In orbit

Individual stars in the cluster, attracted by the supermassive black hole, began to shift towards the galactic center. However, instead of scattering into space, they remain gathered together thanks to the gravitational pull of a second black hole located at the center of the cluster. The mass of this black hole can be estimated based on its ability to hold an entire star cluster on a leash. A medium-sized black hole apparently takes about 100 years to orbit the central black hole. This means that long-term observations over many years will allow us to “see” it.