December 27, 2004, a burst of gamma rays arrived in our solar system from SGR 1806-20 (depicted in artist's impression). The explosion was so powerful that it affected the Earth's atmosphere at a distance of over 50,000 light years

A neutron star is a cosmic body, which is one of the possible results of evolution, consisting mainly of a neutron core covered with a relatively thin (∼1 km) crust of matter in the form of heavy atomic nuclei and electrons. The masses of neutron stars are comparable to that of , but the typical radius of a neutron star is only 10-20 kilometers. Therefore, the average density of the substance of such an object is several times higher than the density of the atomic nucleus (which for heavy nuclei is on average 2.8·10 17 kg/m³). Further gravitational compression of the neutron star is prevented by the pressure of nuclear matter arising due to the interaction of neutrons.

Many neutron stars have extremely high rotation speeds, up to a thousand revolutions per second. Neutron stars arise from stellar explosions.

The masses of most neutron stars with reliably measured masses are 1.3-1.5 solar masses, which is close to the Chandrasekhar limit. Theoretically, neutron stars with masses from 0.1 to about 2.5 solar masses are acceptable, but the value of the upper limit mass is currently known very inaccurately. The most massive neutron stars known are Vela X-1 (with a mass of at least 1.88±0.13 solar masses at the 1σ level, which corresponds to a significance level of α≈34%), PSR J1614-2230ruen (with a mass estimate of 1.97 ±0.04 solar), and PSR J0348+0432ruen (with a mass estimate of 2.01±0.04 solar). Gravity in neutron stars is balanced by the pressure of the degenerate neutron gas, the maximum value of the mass of a neutron star is set by the Oppenheimer-Volkoff limit, the numerical value of which depends on the (still poorly known) equation of state of matter in the star's core. There are theoretical premises that with an even greater increase in density, the degeneration of neutron stars into quarks is possible.

The structure of a neutron star.

The magnetic field on the surface of neutron stars reaches a value of 10 12 -10 13 G (for comparison, the Earth has about 1 G), it is the processes in the magnetospheres of neutron stars that are responsible for the radio emission of pulsars. Since the 1990s, some neutron stars have been identified as magnetars - stars with magnetic fields of the order of 10 14 G and higher. Such magnetic fields (exceeding the “critical” value of 4.414 10 13 G, at which the energy of interaction of an electron with a magnetic field exceeds its rest energy mec²) introduce qualitatively new physics, since specific relativistic effects, polarization of the physical vacuum, etc. become significant.

By 2012, about 2000 neutron stars had been discovered. About 90% of them are single. In total, 10 8 -10 9 neutron stars can exist in ours, that is, about one per thousand ordinary stars. Neutron stars are characterized by high speed (usually hundreds of km/s). As a result of the accretion of cloud matter, the neutron star can be visible in this situation in different spectral ranges, including optical, which accounts for about 0.003% of the emitted energy (corresponding to magnitude 10).

Gravitational deflection of light (more than half of the surface is visible due to relativistic deflection of light)

Neutron stars are one of the few classes of cosmic objects that were theoretically predicted before their discovery by observers.

In 1933, astronomers Walter Baade and Fritz Zwicky suggested that a neutron star could form as a result of a supernova explosion. Theoretical calculations at that time showed that the radiation from a neutron star was too weak to be detected. Interest in neutron stars intensified in the 1960s, when X-ray astronomy began to develop, as theory predicted that their thermal emission maximum would occur in the soft X-ray region. However, unexpectedly they were discovered in radio observations. In 1967, Jocelyn Bell, a graduate student of E. Huish, discovered objects emitting regular pulses of radio waves. This phenomenon was explained by the narrow directionality of the radio beam from a rapidly rotating object - a kind of “cosmic radio beacon”. But any ordinary star would collapse at such a high rotation speed. Only neutron stars were suitable for the role of such beacons. The pulsar PSR B1919+21 is believed to be the first neutron star discovered.

The interaction of a neutron star with the surrounding matter is determined by two main parameters and, as a consequence, their observable manifestations: the period (speed) of rotation and the magnitude of the magnetic field. Over time, the star uses up its rotational energy and its rotation slows down. The magnetic field also weakens. For this reason, a neutron star can change its type during its life. Below is the nomenclature of neutron stars in descending order of rotation speed, according to the monograph by V.M. Lipunova. Because the theory of pulsar magnetospheres is still evolving, alternative theoretical models exist.

Strong magnetic fields and short rotation period. In the simplest model of the magnetosphere, the magnetic field rotates solidly, that is, with the same angular velocity as the body of the neutron star. At a certain radius, the linear speed of rotation of the field approaches the speed of light. This radius is called the "light cylinder radius". Beyond this radius, an ordinary dipole field cannot exist, so the field strength lines break off at this point. Charged particles moving along magnetic field lines can leave the neutron star through such cliffs and fly into interstellar space. A neutron star of this type “ejects” (from the French éjecter - to eject, push out) relativistic charged particles that emit in the radio range. Ejectors are observed as radio pulsars.

Propeller

The rotation speed is no longer sufficient for the ejection of particles, so such a star cannot be a radio pulsar. However, the rotation speed is still high, and the matter surrounding the neutron star captured by the magnetic field cannot fall, that is, accretion of matter does not occur. Neutron stars of this type have virtually no observable manifestations and are poorly studied.

Accrector (X-ray pulsar)

The rotation speed is reduced to such a level that nothing now prevents matter from falling onto such a neutron star. The falling matter, already in the state of plasma, moves along the magnetic field lines and hits the solid surface of the neutron star’s body in the region of its poles, heating up to tens of millions of degrees. Matter heated to such high temperatures glows brightly in the X-ray range. The region in which the collision of falling matter with the surface of the neutron star body occurs is very small - only about 100 meters. Due to the rotation of the star, this hot spot periodically disappears from view, and regular pulsations of X-ray radiation are observed. Such objects are called X-ray pulsars.

Georotator

The rotation speed of such neutron stars is low and does not prevent accretion. But the dimensions of the magnetosphere are such that the plasma is stopped by the magnetic field before it is captured by gravity. A similar mechanism operates in the Earth’s magnetosphere, which is why this type of neutron star got its name.

Magnetar

A neutron star with an exceptionally strong magnetic field (up to 10 11 T). The theoretical existence of magnetars was predicted in 1992, and the first evidence of their real existence was obtained in 1998 when observing a powerful burst of gamma-ray and X-ray radiation from the source SGR 1900+14 in the constellation Aquila. The lifetime of magnetars is about 1,000,000 years. Magnetars have the strongest magnetic field in .

Magnetars are a little-studied type of neutron star due to the fact that few are close enough to Earth. Magnetars are about 20-30 km in diameter, but most have masses greater than the mass of the Sun. The magnetar is so compressed that a pea of ​​its matter would weigh more than 100 million tons. Most of the known magnetars rotate very quickly, at least several rotations around their axis per second. Observed in gamma radiation close to X-rays, it does not emit radio emission. The life cycle of a magnetar is quite short. Their strong magnetic fields disappear after about 10,000 years, after which their activity and emission of X-rays cease. According to one assumption, up to 30 million magnetars could have formed in our galaxy during its entire existence. Magnetars are formed from massive stars with an initial mass of about 40 M☉.

The shocks generated on the surface of the magnetar cause huge vibrations in the star; the fluctuations in the magnetic field that accompany them often lead to huge bursts of gamma radiation, which were recorded on Earth in 1979, 1998 and 2004.

As of May 2007, twelve magnetars were known, with three more candidates awaiting confirmation. Examples of known magnetars:

SGR 1806-20, located 50,000 light-years from Earth on the opposite side of our Milky Way galaxy in the constellation Sagittarius.
SGR 1900+14, 20,000 light years distant, located in the constellation Aquila. After a long period of low emission emissions (significant explosions only in 1979 and 1993), it became active in May-August 1998, and the explosion detected on August 27, 1998 was of sufficient force to force the NEAR Shoemaker spacecraft to be shut down to prevent damage. On May 29, 2008, NASA's Spitzer telescope discovered rings of matter around this magnetar. It is believed that this ring was formed by an explosion observed in 1998.
1E 1048.1-5937 is an anomalous X-ray pulsar located 9000 light years away in the constellation Carina. The star from which the magnetar formed had a mass 30-40 times greater than that of the Sun.
A complete list is given in the magnetar catalog.

As of September 2008, ESO reports the identification of an object initially thought to be a magnetar, SWIFT J195509+261406; it was originally identified by gamma-ray bursts (GRB 070610)

The objects discussed in the article were discovered by accident, although scientists L. D. Landau and R. Oppenheimer predicted their existence back in 1930. We are talking about neutron stars. The characteristics and features of these cosmic luminaries will be discussed in the article.

Neutron and the star of the same name

After the prediction in the 30s of the 20th century about the existence of neutron stars and after the discovery of the neutron (1932), Baade V., together with Zwicky F., in 1933, at a congress of physicists in America, announced the possibility of the formation of an object called neutron star. This is a cosmic body that appears during a supernova explosion.

However, all calculations were only theoretical, since it was not possible to prove such a theory in practice due to the lack of appropriate astronomical equipment and the too small size of the neutron star. But in 1960, X-ray astronomy began to develop. Then, quite unexpectedly, neutron stars were discovered thanks to radio observations.

Opening

The year 1967 was significant in this area. Bell D., as a graduate student of Huish E., was able to discover a cosmic object - a neutron star. This is a body emitting constant radiation of radio wave pulses. The phenomenon was compared to a cosmic radio beacon due to the narrow directionality of the radio beam, which came from a very fast rotating object. The fact is that any other standard star would not be able to maintain its integrity at such a high rotational speed. Only neutron stars are capable of this, among which the first discovered was the pulsar PSR B1919+21.

The fate of massive stars is very different from small ones. In such luminaries there comes a moment when the gas pressure no longer balances the gravitational forces. Such processes lead to the fact that the star begins to shrink (collapse) without limit. With a star mass 1.5-2 times greater than the Sun, collapse will be inevitable. During the compression process, the gas inside the stellar core heats up. At first everything happens very slowly.

Collapse

Reaching a certain temperature, a proton can turn into neutrinos, which immediately leave the star, taking energy with them. The collapse will intensify until all protons turn into neutrinos. This creates a pulsar, or neutron star. This is a collapsing core.

During the formation of a pulsar, the outer shell receives compression energy, which will then be at a speed of more than one thousand km/sec. thrown into space. This creates a shock wave that can lead to new star formation. This one will be billions of times larger than the original. After this process, over a period of one week to a month, the star emits light in an amount exceeding an entire galaxy. Such a celestial body is called a supernova. Its explosion leads to the formation of a nebula. At the center of the nebula is a pulsar, or neutron star. This is the so-called descendant of a star that exploded.

Visualization

In the depths of all space, amazing events take place, among which is the collision of stars. Thanks to a sophisticated mathematical model, NASA scientists were able to visualize the riot of enormous amounts of energy and the degeneration of matter involved in it. An incredibly powerful picture of a cosmic cataclysm plays out before the eyes of observers. The probability that a collision of neutron stars will occur is very high. The meeting of two such luminaries in space begins with their entanglement in gravitational fields. Possessing enormous mass, they exchange hugs, so to speak. Upon collision, a powerful explosion occurs, accompanied by an incredibly powerful release of gamma radiation.

If we consider a neutron star separately, then it is the remnant of a supernova explosion, whose life cycle is ending. The mass of a dying star is 8-30 times greater than that of the sun. The universe is often illuminated by supernova explosions. The probability that neutron stars will be found in the universe is quite high.

Meeting

It is interesting that when two stars meet, the development of events cannot be foreseen unambiguously. One of the options is described by a mathematical model proposed by NASA scientists from the Space Flight Center. The process begins with two neutron stars located at a distance of approximately 18 km from each other in outer space. By cosmic standards, neutron stars with a mass of 1.5-1.7 times the Sun are considered tiny objects. Their diameter varies within 20 km. Due to this discrepancy between volume and mass, a neutron star has a strong gravitational and magnetic field. Just imagine: a teaspoon of matter from a neutron star weighs as much as the entire Mount Everest!

Degeneration

The incredibly high gravitational waves of a neutron star around it are the reason why matter cannot exist in the form of individual atoms, which begin to collapse. The matter itself transforms into degenerate neutron matter, in which the structure of the neutrons themselves will not allow the star to pass into a singularity and then into a black hole. If the mass of degenerate matter begins to increase due to addition to it, then gravitational forces will be able to overcome the resistance of neutrons. Then nothing will prevent the destruction of the structure formed as a result of the collision of neutron stellar objects.

Mathematical model

By studying these celestial objects, scientists came to the conclusion that the density of a neutron star is comparable to the density of matter in the nucleus of an atom. Its indicators range from 1015 kg/m³ to 1018 kg/m³. Thus, the independent existence of electrons and protons is impossible. The star's matter practically consists of only neutrons.

The created mathematical model demonstrates how powerful periodic gravitational interactions that occur between two neutron stars break through the thin shell of the two stars and eject huge amounts of radiation (energy and matter) into the space surrounding them. The process of rapprochement occurs very quickly, literally in a split second. As a result of the collision, a toroidal ring of matter is formed with a newborn black hole in the center.

Important

Modeling such events is important. Thanks to them, scientists were able to understand how a neutron star and a black hole are formed, what happens when stars collide, how supernovae are born and die, and many other processes in outer space. All these events are the source of the appearance of the heaviest chemical elements in the Universe, even heavier than iron, unable to be formed in any other way. This indicates the very important importance of neutron stars throughout the Universe.

The rotation of a celestial object of enormous volume around its axis is amazing. This process causes collapse, but at the same time the mass of the neutron star remains practically the same. If we imagine that the star will continue to contract, then, according to the law of conservation of angular momentum, the angular velocity of rotation of the star will increase to incredible values. If a star needed about 10 days to complete a full revolution, then as a result it will complete the same revolution in 10 milliseconds! These are incredible processes!

Development of collapse

Scientists are studying such processes. Perhaps we will witness new discoveries that still seem fantastic to us! But what could happen if we imagine the development of the collapse further? To make it easier to imagine, let’s take for comparison the neutron star/Earth pair and their gravitational radii. So, with continuous compression, a star can reach a state where neutrons begin to turn into hyperons. The radius of the celestial body will become so small that we will see a lump of a superplanetary body with the mass and gravitational field of a star. This can be compared to how if the earth became the size of a ping-pong ball, and the gravitational radius of our luminary, the Sun, were equal to 1 km.

If we imagine that a small lump of stellar matter has the attraction of a huge star, then it is capable of holding an entire planetary system near it. But the density of such a celestial body is too high. Rays of light gradually stop breaking through it, the body seems to go out, it ceases to be visible to the eye. Only the gravitational field does not change, which warns that there is a gravitational hole here.

Discoveries and observations

The first time neutron star mergers were recorded was quite recently: August 17. Two years ago, a black hole merger was detected. This is such an important event in the field of astrophysics that observations were simultaneously carried out by 70 space observatories. Scientists were able to verify the correctness of the hypotheses about gamma-ray bursts; they were able to observe the synthesis of heavy elements previously described by theorists.

This widespread observation of the gamma-ray burst, gravitational waves and visible light made it possible to determine the region in the sky where the significant event occurred and the galaxy where these stars were located. This is NGC 4993.

Of course, astronomers have been observing short ones for a long time, but until now they could not say for sure about their origin. Behind the main theory was a version of the merger of neutron stars. Now it has been confirmed.

To describe a neutron star using mathematics, scientists turn to the equation of state that relates density to pressure of matter. However, there are a lot of such options, and scientists simply do not know which of the existing ones will be correct. It is hoped that gravitational observations will help resolve this issue. At the moment, the signal has not given a clear answer, but it already helps to estimate the shape of the star, which depends on the gravitational attraction to the second body (star).

NEUTRON STAR
a star made primarily of neutrons. A neutron is a neutral subatomic particle, one of the main components of matter. The hypothesis about the existence of neutron stars was put forward by astronomers W. Baade and F. Zwicky immediately after the discovery of the neutron in 1932. But this hypothesis was confirmed by observations only after the discovery of pulsars in 1967.
see also PULSAR. Neutron stars are formed as a result of the gravitational collapse of normal stars with masses several times greater than the Sun. The density of a neutron star is close to the density of an atomic nucleus, i.e. 100 million times higher than the density of ordinary matter. Therefore, with its enormous mass, a neutron star has a radius of only approx. 10 km. Due to the small radius of a neutron star, the force of gravity on its surface is extremely high: about 100 billion times higher than on Earth. This star is kept from collapse by the “degeneracy pressure” of dense neutron matter, which does not depend on its temperature. However, if the mass of a neutron star becomes higher than about 2 solar, then the force of gravity will exceed this pressure and the star will not be able to withstand the collapse.
see also GRAVITATIONAL COLLAPSE. Neutron stars have a very strong magnetic field, reaching 10 12-10 13 G on the surface (for comparison: the Earth has about 1 G). Two different types of celestial objects are associated with neutron stars.
Pulsars (radio pulsars). These objects emit pulses of radio waves strictly regularly. The mechanism of radiation is not completely clear, but it is believed that a rotating neutron star emits a radio beam in a direction associated with its magnetic field, the axis of symmetry of which does not coincide with the axis of rotation of the star. Therefore, rotation causes the rotation of the radio beam, which is periodically directed towards the Earth.
X-ray doubles. Pulsating X-ray sources are also associated with neutron stars that are part of a binary system with a massive normal star. In such systems, gas from the surface of a normal star falls onto a neutron star, accelerating to enormous speed.
When hitting the surface of a neutron star, the gas releases 10-30% of its rest energy, while during nuclear reactions this figure does not reach 1%. The surface of a neutron star heated to a high temperature becomes a source of X-ray radiation. However, the fall of gas does not occur uniformly over the entire surface: the strong magnetic field of a neutron star captures the falling ionized gas and directs it to the magnetic poles, where it falls, like into a funnel. Therefore, only the polar regions become very hot, and on a rotating star they become sources of X-ray pulses. Radio pulses from such a star are no longer received, since the radio waves are absorbed in the gas surrounding it. Compound.

The density of a neutron star increases with depth. Under a layer of atmosphere only a few centimeters thick there is a liquid metal shell several meters thick, and below that there is a solid crust a kilometer thick. The substance of the bark resembles ordinary metal, but is much denser. In the outer part of the bark it is mainly iron; With depth, the proportion of neutrons in its composition increases. Where the density reaches approx. 4*10 11 g/cm3, the proportion of neutrons increases so much that some of them are no longer part of the nuclei, but form a continuous medium. There, the substance is like a “sea” of neutrons and electrons, in which the nuclei of atoms are interspersed. And with a density of approx. 2*10 14 g/cm3 (density of the atomic nucleus), individual nuclei disappear altogether and what remains is a continuous neutron “liquid” with an admixture of protons and electrons. It is likely that neutrons and protons behave like a superfluid liquid, similar to liquid helium and superconducting metals in earthly laboratories.
see also
At even higher densities, the most unusual forms of matter are formed in a neutron star. Perhaps neutrons and protons decay into even smaller particles - quarks; It is also possible that many pi-mesons are born, which form the so-called pion condensate.
ELEMENTARY PARTICLES;
SUPERCONDUCTIVITY;
SUPERFLUIDITY.
LITERATURE

Dyson F., Ter Haar D. Neutron stars and pulsars. M., 1973 Lipunov V.M. Astrophysics of neutron stars. M., 1987. 2000 .

Collier's Encyclopedia. - Open Society

NEUTRON STAR, a very small star with high density, consisting of NEUTRONS. It is the last stage in the evolution of many stars. Neutron stars are formed when a massive star explodes as a supernova, exploding its... ... Scientific and technical encyclopedic dictionary

A star whose matter, according to theoretical concepts, consists mainly of neutrons. Neutronization of matter is associated with the gravitational collapse of a star after its nuclear fuel is exhausted. The average density of neutron stars is 2.1017 ... Big Encyclopedic Dictionary

The structure of a neutron star. A neutron star is an astronomical object that is one of the final products ... Wikipedia

A star whose matter, according to theoretical concepts, consists mainly of neutrons. The average density of such a star is Neutron star 2·1017 kg/m3, the average radius is 20 km. Detected by pulsed radio emission, see Pulsars... Astronomical Dictionary

A star whose matter, according to theoretical concepts, consists mainly of neutrons. Neutronization of matter is associated with the gravitational collapse of a star after its nuclear fuel is exhausted. Average density of a neutron star... ... encyclopedic Dictionary

A hydrostatically equilibrium star, in which the swarm consists mainly. from neutrons. Formed as a result of the transformation of protons into neutrons under gravitational forces. collapse at the final stages of evolution of fairly massive stars (with a mass several times greater than... ... Natural science. encyclopedic Dictionary

Neutron star- one of the stages of the evolution of stars, when, as a result of gravitational collapse, it is compressed to such small sizes (the radius of the ball is 10-20 km) that electrons are pressed into the nuclei of atoms and neutralize their charge, all the matter of the star becomes... ... The beginnings of modern natural science

Culver's Neutron Star. It was discovered by astronomers from the Pennsylvania State University in the USA and the Canadian McGill University in the constellation Ursa Minor. The star is unusual in its characteristics and is unlike any other... ... Wikipedia

- (English runaway star) a star that moves at an abnormally high speed in relation to the surrounding interstellar medium. The proper motion of such a star is often indicated precisely relative to the stellar association, a member of which... ... Wikipedia

The hypothesis about the existence of neutron stars was put forward by astronomers W. Baade and F. Zwicky immediately after the discovery of the neutron in 1932. But this hypothesis was confirmed by observations only after the discovery of pulsars in 1967.

Neutron stars are formed as a result of the gravitational collapse of normal stars with masses several times greater than the Sun. The density of a neutron star is close to the density of an atomic nucleus, i.e. 100 million times higher than the density of ordinary matter. Therefore, with its enormous mass, a neutron star has a radius of only approx. 10 km.

Due to the small radius of a neutron star, the force of gravity on its surface is extremely high: about 100 billion times higher than on Earth. What keeps this star from collapsing is the “degeneracy pressure” of dense neutron matter, which does not depend on its temperature. However, if the mass of a neutron star becomes higher than about 2 solar, then the force of gravity will exceed this pressure and the star will not be able to withstand collapse.

Neutron stars have a very strong magnetic field, reaching 10 12 –10 13 G on the surface (for comparison: the Earth has about 1 G). Two different types of celestial objects are associated with neutron stars.

Pulsars

(radio pulsars). These objects emit pulses of radio waves strictly regularly. The mechanism of radiation is not completely clear, but it is believed that a rotating neutron star emits a radio beam in a direction associated with its magnetic field, the axis of symmetry of which does not coincide with the axis of rotation of the star. Therefore, rotation causes the rotation of the radio beam, which is periodically directed towards the Earth.

X-ray doubles.

Pulsating X-ray sources are also associated with neutron stars that are part of a binary system with a massive normal star. In such systems, gas from the surface of a normal star falls onto a neutron star, accelerating to enormous speed. When hitting the surface of a neutron star, the gas releases 10–30% of its rest energy, while during nuclear reactions this figure does not reach 1%. The surface of a neutron star heated to a high temperature becomes a source of X-ray radiation. However, the fall of gas does not occur uniformly over the entire surface: the strong magnetic field of a neutron star captures the falling ionized gas and directs it to the magnetic poles, where it falls, like into a funnel. Therefore, only the polar regions become very hot, and on a rotating star they become sources of X-ray pulses. Radio pulses from such a star are no longer received, since the radio waves are absorbed in the gas surrounding it.

Compound.

The density of a neutron star increases with depth. Under a layer of atmosphere only a few centimeters thick there is a liquid metal shell several meters thick, and below that there is a solid crust a kilometer thick. The substance of the bark resembles ordinary metal, but is much denser. In the outer part of the bark it is mainly iron; With depth, the proportion of neutrons in its composition increases. Where the density reaches approx. 4H 10 11 g/cm 3 , the proportion of neutrons increases so much that some of them are no longer part of the nuclei, but form a continuous medium. There, the substance is like a “sea” of neutrons and electrons, in which the nuclei of atoms are interspersed. And with a density of approx. 2H 10 14 g/cm 3 (density of the atomic nucleus), individual nuclei disappear altogether and what remains is a continuous neutron “liquid” with an admixture of protons and electrons. It is likely that neutrons and protons behave like a superfluid liquid, similar to liquid helium and superconducting metals in earthly laboratories.

Introduction

Throughout its history, humanity has not stopped trying to understand the universe. The universe is the totality of everything that exists, all the material particles of space between these particles. According to modern ideas, the age of the Universe is about 14 billion years.

The size of the visible part of the universe is approximately 14 billion light years (one light year is the distance that light travels in a vacuum in one year). Some scientists estimate the extent of the universe to be 90 billion light years. In order to make it convenient to operate such huge distances, a value called Parsec is used. A parsec is the distance from which the average radius of the Earth's orbit, perpendicular to the line of sight, is visible at an angle of one arcsecond. 1 parsec = 3.2616 light years.

There are a huge number of different objects in the universe, the names of which are familiar to many, such as planets and satellites, stars, black holes, etc. Stars are very diverse in their brightness, size, temperature, and other parameters. Stars include objects such as white dwarfs, neutron stars, giants and supergiants, quasars and pulsars. The centers of galaxies are of particular interest. According to modern ideas, a black hole is suitable for the role of the object located in the center of the galaxy. Black holes are products of the evolution of stars, unique in their properties. The experimental reliability of the existence of black holes depends on the validity of the general theory of relativity.

In addition to galaxies, the universe is filled with nebulae (interstellar clouds consisting of dust, gas and plasma), cosmic microwave background radiation that permeates the entire universe, and other little-studied objects.

Neutron stars

A neutron star is an astronomical object, which is one of the final products of the evolution of stars, consisting mainly of a neutron core covered with a relatively thin (? 1 km) crust of matter in the form of heavy atomic nuclei and electrons. The masses of neutron stars are comparable to the mass of the Sun, but the typical radius is only 10-20 kilometers. Therefore, the average density of the matter of such a star is several times higher than the density of the atomic nucleus (which for heavy nuclei is on average 2.8 * 1017 kg/m?). Further gravitational compression of the neutron star is prevented by the pressure of nuclear matter arising due to the interaction of neutrons.

Many neutron stars have extremely high rotation rates, up to thousands of revolutions per second. It is believed that neutron stars are born during supernova explosions.

The gravitational forces in neutron stars are balanced by the pressure of the degenerate neutron gas, the maximum value of the mass of a neutron star is set by the Oppenheimer-Volkoff limit, the numerical value of which depends on the (still poorly known) equation of state of matter in the star's core. There are theoretical premises that with an even greater increase in density, the degeneration of neutron stars into quarks is possible.

The magnetic field on the surface of neutron stars reaches a value of 1012-1013 G (Gauss is a unit of measurement of magnetic induction), and it is the processes in the magnetospheres of neutron stars that are responsible for the radio emission of pulsars. Since the 1990s, some neutron stars have been identified as magnetars—stars with magnetic fields of the order of 1014 Gauss or higher. Such fields (exceeding the “critical” value of 4.414 1013 G, at which the energy of interaction of an electron with a magnetic field exceeds its rest energy) introduce qualitatively new physics, since specific relativistic effects, polarization of the physical vacuum, etc. become significant.

Classification of neutron stars

Two main parameters characterizing the interaction of neutron stars with the surrounding matter and, as a consequence, their observational manifestations are the rotation period and the magnitude of the magnetic field. Over time, the star expends its rotational energy, and its rotation period increases. The magnetic field also weakens. For this reason, a neutron star can change its type during its life.

Ejector (radio pulsar) - strong magnetic fields and short rotation period. In the simplest model of the magnetosphere, the magnetic field rotates solidly, that is, with the same angular velocity as the neutron star itself. At a certain radius, the linear speed of rotation of the field approaches the speed of light. This radius is called the radius of the light cylinder. Beyond this radius, an ordinary dipole field cannot exist, so the field strength lines break off at this point. Charged particles moving along magnetic field lines can leave the neutron star through such cliffs and fly away to infinity. A neutron star of this type ejects (spews out) relativistic charged particles that emit in the radio range. To an observer, ejectors look like radio pulsars.

Propeller - the rotation speed is no longer sufficient for the ejection of particles, so such a star cannot be a radio pulsar. However, it is still large, and the matter surrounding the neutron star captured by the magnetic field cannot fall, that is, accretion of matter does not occur. Neutron stars of this type have virtually no observable manifestations and are poorly studied.

Accretor (X-ray pulsar) - the rotation speed is reduced to such an extent that nothing now prevents matter from falling onto such a neutron star. The plasma, falling, moves along the magnetic field lines and hits a solid surface in the region of the poles of the neutron star, heating up to tens of millions of degrees. Matter heated to such high temperatures glows in the X-ray range. The region in which the falling matter collides with the surface of the star is very small - only about 100 meters. Due to the rotation of the star, this hot spot periodically disappears from view, which the observer perceives as pulsations. Such objects are called X-ray pulsars.

Georotator - the rotation speed of such neutron stars is low and does not prevent accretion. But the dimensions of the magnetosphere are such that the plasma is stopped by the magnetic field before it is captured by gravity. A similar mechanism operates in the Earth’s magnetosphere, which is why this type got its name.