This type stars are extremely rare in nature. Not too long ago, the question of their location and their immediate occurrence left the learned astrologers in limbo. But thanks to the Very Large Telescope (VLT) located at the Panama Observatory in Chile, belonging to the European Southern Observatory, and the data collected with it, astronomers can now safely believe that they have finally been able to solve one of the many mysteries of such an incomprehensible for us space.

As already noted above in this article, magnetars are a very rare type of neutron stars, which are characterized by tremendous strength (they are the strongest known objects in the entire Universe) of the magnetic field. One of the features of these stars is that they are relatively small in size and have an incredible density. Scientists suggest that the mass of just one piece of this matter, the size of a small glass ball, can reach more than one billion tons.

This type of star can form when massive stars begin to collapse under the force of their own gravity.

Magnetars in our galaxy

The Milky Way has about three dozen magnetars. The object studied with the Very Large Telescope is located in a cluster of stars called Westerlund-1, namely in the southern part of the constellation of the Altar, which is located only 16 thousand light-years from us. The star, which has now become a magnetar, was about 40-45 times larger than our Sun. This observation led scientists into confusion: after all, the stars of such large sizes, in their opinion, should collapse into black holes.

However, the fact that the star, previously called CXOU J1664710.2-455216, turned into a magnetar as a result of its own collapse, tormented astronomers for several years. But still, scientists assumed that preceded such a very atypical and unusual phenomenon.

The open star cluster Westerlund 1. The images show a magnetar and its companion star, torn from it by an explosion. Source: ESO

Relatively recently, in 2010, an assumption was put forward for discussion that the magnetar appeared as a result of a close interaction between two massive stars. Following this assumption, the stars turned one around the other, which caused the transformation. These objects were so close that they would easily fit into such a small space as the distance between the orbits of the Sun and the Earth.

But, until recently, scientists dealing with this problem could not find any evidence of the mutual and so close coexistence of two stars in the proposed model of a binary system. But with the help of the Very Large Telescope, astronomers were able to study in more detail the part of the sky of interest to them in which star clusters are located and find suitable objects whose speed is quite high (“runaway” or “runaway” stars). According to one theory, it is believed that such objects were thrown from their native orbits as a result of the explosion of supernovae that form magnetars. And, in fact, this star was found, which scientists later called Westerlund 1x5.

The author who published the study data, Ben Ritchie, explains the role of the found "running" star as follows:
“Not only does the star we found have an enormous speed in motion, which was quite possibly caused by a supernova explosion, but here it seems to be a tandem of its surprisingly small mass, high luminosity and its carbon-rich components. This is surprising, because these qualities are rarely combined in one object. All this indicates that Westerlund 1x5 could indeed have formed in a binary system.”

With the collected data on this star, a team of astronomers reconstructed the alleged model of the appearance of the magnetar. According to the proposed scheme, the fuel supply of the smaller star was higher than that of its "companion". Thus, the small star began to attract the upper balls of the large one, which led to the integration of a strong magnetic field.

After some time, the small object became larger than its binary companion, which caused the reverse process of transferring the upper layers. According to one of the participants in the experiment, Francisco Najarro, these actions of the objects under study are exactly reminiscent of the well-known children's game "Pass it to another." The goal of the game is to wrap an object in several layers of paper and pass it around a circle of children. Each participant must unwrap one layer of the wrapper, finding an interesting trinket in the process.

In theory, the larger of the two stars turns into a smaller one and is discarded from the binary system, at the moment when the second star quickly turns around its axis and turns into a supernova. In this situation, the "running" star, Westerlund 1x5, is the second star in the binary pair (it carries all the known features of the described process).
Scientists who have been studying this fascinating process, based on the data they collected during the experiment, came to the conclusion that very fast rotation and mass transfer between binary stars is the key to the formation of rare neutron stars, also known as magnetars.

Video about the magnetar:

Artist's illustration showing a magnetar in a very rich and young star cluster. Image Credit & Copyright: ESO / L. Calçada.

Perhaps you think the universe is perfect for life. However, it is not. Almost the entire universe is a terrible and hostile place, and we were just lucky to be born on a practically harmless planet in a remote area. Milky Way.

Here on Earth you can live a long and happy life, but there are places in the Universe where you won't last even a couple of seconds. Nothing is more deadly than the objects that supernovae leave behind: neutron stars.

As you know, neutron stars form when stars more massive than our Sun explode as supernovae. When these stars die, they cannot resist the powerful gravity and shrink into objects several tens of kilometers in diameter. As a result of such huge pressure, neutrons are formed inside the object.

In most cases, you get neutron stars of the first type - pulsars. A pulsar is a tiny neutron star that rotates at a tremendous speed, sometimes reaching several hundred revolutions per second.

However, about one in ten neutron stars becomes something very strange indeed. It becomes a magnetar - the most mysterious and terrible object in the universe. You've probably heard this word, but what is it?

As I said, magnetars are neutron stars formed as a result of supernova explosions. But what happens during their formation so unusual that their magnetic field exceeds the magnetic fields of any other objects by hundreds, thousands and even millions of times? In fact, astronomers don't know exactly what makes magnetars' magnetic fields so powerful.

An artist's impression of the merger of two neutron stars. Credit & Copyright: University of Warwick/Mark Garlick.

According to the first theory, if a neutron star is formed by rotating rapidly, then the joint work of convection and rotation, which has a dominant influence in the first few seconds of the existence of a neutron star, can lead to the formation of a powerful magnetic field. This process is known to scientists as the “active dynamo”.

However, as a result of recent research, astronomers have proposed a second theory for the formation of magnetars. Researchers have discovered a magnetar that will leave our galaxy in the future. We have already seen examples of runaway stars, and they all acquired their trajectory as a result of a supernova explosion in a binary system. In other words, this magnetar was also part of a binary system.

In such a system, two stars orbit each other closer than the Earth orbits the Sun. It's so close that the material in the stars can flow back and forth. First, the large star begins to swell and transfer material to the smaller star. This increase in mass leads to an increase in the size of the smaller star and the material begins to flow back to the first star.

In the end, one of the stars explodes and throws another star away from the Milky Way, and an unusual neutron star remains at the site of the explosion, that is, all these binary interactions turned the neutron star into a magnetar. Perhaps this is the solution to the magnetar riddle.

The magnetic field of a magnetar will really make you scared. The magnetic induction in the center of the Earth is about 25 gauss, but on the surface of the planet it does not exceed 0.5 gauss. An ordinary neutron star has a magnetic field with a magnetic induction of several trillion gauss. Magnetars are 1000 times more powerful than neutron stars.

Starquakes destroying the surface of a neutron star as imagined by an artist. Image Credit & Copyright: Darlene McElroy of LANL.

One of the most interesting features magnetars is that they can experience starquakes. You know that there are earthquakes, but on the stars, they will be starquakes. When magnetars form, they have a denser outer shell. This "neutron crust" can crack like tectonic plates on Earth. When this happens, the magnetar emits a beam of radiation that we can see at great distances.

In fact, the most powerful starquake ever recorded happened to a magnetar called SGR 1806-20, which is located about 50,000 light-years from Earth. In a tenth of a second, this magnetar released more energy than the Sun produces in 100,000 years. And it wasn't even an explosion of the whole object, it was just a small crack on the surface of the magnetar.

Magnetars are amazing and dangerous objects. Fortunately, they are very far away, and you do not need to worry about their impact on your life.

Some stars are so strongly magnetized that they emit giant flashes due to the energy of the magnetic field and significantly change quantum properties vacuum. "Starquake" on the magnetar releases a huge amount of electromagnetic energy (equivalent to the energy of an earthquake with a magnitude of 21 points) and ejects a hot plasma ball, which is captured magnetic field.

On March 5, 1979, after dropping landers into the poisonous atmosphere of Venus, the Soviet space stations Venera 11 and Venera 12 continued their flight in elliptical orbits through the inner solar system. The readings of the radiation counters aboard both stations fluctuated within 100 readings per second. However, at 10:51 Central European Time (EST), a stream of gamma radiation hit the devices. In a fraction of a millisecond, the radiation level exceeded 200 thousand counts per second. After 11 sec. gamma-ray flux covered NASA's Helios-2 space probe, which was also moving in orbit around the Sun. It became clear that a flat front of high-energy radiation passed through the solar system. Soon he reached Venus, and on the Pioneer VenusOrbiter satellite orbiting it, the detector went off scale. A few seconds later, the stream reached the Earth and was registered by three Vela satellites of the US Department of Defense, Soviet satellite Prognoz-7 and the Einstein space observatory. Finally, on its way through the solar system, the wave front hit the International Sun-Earth Explorer space station.

The burst of high-energy hard gamma radiation was 100 times more intense than all the previous ones coming from outside the solar system, and lasted only 0.2 seconds. It was followed by a stream of soft x-ray and gamma radiation, pulsing with a period of 8 sec. and died out after three minutes. 14.5 hours later at 01:17 on March 6 at the same point celestial sphere another, but weaker burst of gamma rays was observed. Over the next four years, a group of scientists from the Leningrad Institute of Physics and Technology. A.F. Ioffe, under the leadership of Evgeny Mazets, registered 16 more outbreaks. They differed in intensity, but were weaker and shorter than the burst on March 5, 1979.

Astronomers have never seen anything like it. First, new bursts were included in the catalogs of already well-known and studied gamma-ray bursts (Gamma-Ray Bursts, GRB), although they differed from them in a number of ways. In the 80s. Kevin C. Hurley of the University of California at Berkeley found that similar explosions occurred in two more regions of the sky. Flares from all these sources were repeated, in contrast to GRBs, which flared only once (see Fig. No. 4 "In the world of science." Neil Gerels, Luigi Piroi Peter Leonard "The Brightest Explosions in the Universe"). In July 1986, at a conference in Toulouse, astronomers agreed on the location of these sources in the sky and named them "Soft Gamma Repeaters" (SGR).

REVIEW: SUPERMAGNETIZED NEUTRON STARS

• Astronomers have discovered several stars emitting powerful flashes of gamma and X-rays that could be millions of times brighter than any other known repetitive flashes. The huge magnitude of these energies and pulsations of radiation indicate neutron stars - the second most extreme (after black holes) type of objects in the Universe.
• These neutron stars have the strongest magnetic fields ever measured, which is why they are called magnetars. The observed flashes can be explained by magnetic instability similar to earthquakes.
• Millions of magnetars are drifting through our galaxy undetected as they remain active for only 10 thousand years.

It took another seven years before Duncan and Thompson, two of the authors of this paper, came up with an explanation for these strange objects, and it wasn't until 1988 that Cuveliotou and her group found compelling evidence to support their proposed model. Recent observations have shown that all this is related to another type of mysterious celestial bodies known as anomalous X-ray pulsars (Anomalous X-ray Pulsars, AXP).

Neutron stars are the densest known celestial bodies: their mass, slightly exceeding the mass of the Sun, is concentrated in a ball with a diameter of only 20 km. SGR studies have shown that some neutron stars have such a strong magnetic field that it significantly changes the properties of matter inside stars and quantum state vacuum around them, which leads to physical effects not observed elsewhere in the universe.

Nobody expected

Because the burst of radiation in March 1979 was so strong, theorists have suggested that its source is somewhere in our Galaxy at a distance of no more than a few hundred light-years from Earth. In this case, the intensity of X-ray and gamma radiation of the object could lie below the maximum stationary luminosity of the star, which was calculated in 1926 by the English astrophysicist Arthur Eddington. It is determined by the pressure of the radiation passing through the hot outer layers of the star. If the radiation intensity exceeds this maximum, then its pressure will overcome the gravitational force, cause the star's matter to be ejected and violate its stationarity. And the radiation flux, less than the Eddington limit, is not difficult to explain. For example, some theorists have suggested that the burst of radiation could be caused by the impact of a bunch of matter, such as an asteroid or a comet, on a neutron star located nearby.

CANDIDATES FOR MAGNETARS

Twelve objects have been discovered in our Galaxy and its environs that may be magnetars.

Observational data forced scientists to abandon this hypothesis. Each of the space stations noted the time of arrival of the first burst of hard radiation, which allowed a team of astronomers led by Thomas Kline (Thomas Litton Cline) from NASA's Goddard Space Flight Center to triangulate the location of its source. It turned out that it coincides with the Large Magellanic Cloud, a small galaxy about 170 thousand light years away from us. More precisely, the position of the source coincides with the young remnant of a supernova - the luminous remnants of a star that exploded in the Large Magellanic Cloud 5 thousand years ago. If this is not a coincidence, the source must be a thousand times further from the Earth than originally thought, hence its intensity must be a million times the Eddington limit. In March 1979, this source singled out in 0.2 seconds. as much energy as the Sun emits in about 10 thousand years, and this energy was concentrated in the gamma range, and not distributed over the entire spectrum of electromagnetic radiation.

An ordinary star cannot give off that much energy, so the source must be something unusual, such as a black hole or a neutron star. The black hole option was rejected because the radiation intensity changed with a period of about 8 seconds, and the black hole is a structureless object that cannot emit strictly periodic pulses. The association with a supernova remnant further supports the neutron star hypothesis, which is now thought to form when the nuclear fuel in the core of an ordinary high-mass star is depleted and it collapses under the influence of gravity, causing a supernova explosion.

Nevertheless, the identification of the burst source with a neutron star did not solve the problem. Astronomers know of several neutron stars found in supernova remnants, they are radio pulsars - objects that periodically emit pulses of radio waves. However, the source of the burst in March 1979 rotated with a period of about 8 sec, which is much slower than the rotation of all radio pulsars known by that time. And even in “calm” times, it emitted a stationary X-ray flux of such a high intensity that the slowing down of the rotation of a neutron star cannot be explained. It is also strange that the source is noticeably displaced from the center of the supernova remnant. If it was formed in the center of the remnant, then for such a displacement it should have acquired a speed of 1,000 km / s during the explosion, which is not typical for neutron stars.

Finally, the outbreaks themselves seem inexplicable. Bursts of X-rays have been observed in some neutron stars before, but they have never exceeded the Eddington limit. Astronomers attributed them to the processes of thermonuclear burning of hydrogen or helium, or to processes of sudden accretion onto a star. However, the intensity of the SGR flares was unprecedented and a different mechanism was needed to explain it.

Always slowing down

The last gamma-ray burst from a source on March 5, 1979 was recorded in May 1983. Two other SGRs located within our Galaxy were discovered in 1979 and remain active to this day, producing hundreds of flares per year. In 1998, a fourth SGR was discovered. Three of these four objects are likely associated with supernova remnants. Two of them are located near very dense clusters of massive young stars, which suggests their origin from such stars. The fifth SGR candidate has flared up only twice, and its exact position in the sky has not yet been determined.

TWO TYPES OF NEUTRON STARS

The structure of a neutron star based on the theory of nuclear matter. In the crust of a neutron star, which is a structure of atomic nuclei and electrons, starquakes can occur. The nucleus consists mainly of neutrons and possibly quarks. An atmosphere of hot plasma can only extend a few centimeters.

In 1996, researchers Baolian L. Chang, Richard I. Epstein, Robert A. Guyer, and C. AlexY oung at Los Alamos National Laboratory noted that outbreaks SGRs are similar to earthquakes: lower-energy flares occur more frequently. Ersin Gegus, a graduate of the University of Alabama at Huntsville, confirmed this behavior for a large sample of flares from various sources. Similar statistical properties are characteristic of self-organizing systems reaching critical condition, at which a small perturbation can cause chain reaction. This behavior is inherent in a wide variety of systems - from the collapse of sandy slopes to magnetic flares on the Sun.

But why do neutron stars behave this way? The study of radio pulsars, which are rapidly rotating neutron stars with strong magnetic fields, helped answer the question. The magnetic field, maintained by electric currents flowing deep inside the star, rotates with the star. Beams of radio waves are emitted from the magnetic poles of the star and move through space due to its rotation, like beacon lights, as a result of which pulsations are observed. Pulsars also emit streams of charged particles and low-frequency electromagnetic waves, which carry away energy from the angular neutron star, causing its rotation to gradually slow down.

Perhaps the most famous pulsar is in the Crab Nebula, the remnant of a supernova that exploded in 1054. Its rotation period is 33 ms today and increases by 1.3 ms every hundred years. Backward extrapolation gives a value of about 20 ms for the initial period of the pulsar. Scientists believe that the rotation of the pulsar will continue to slow down, and eventually its frequency will become so small that it will not be able to emit radio pulses. The rate of rotation deceleration has been measured for almost all radio pulsars, and, according to the theory, it depends on the magnetic field strength of the star. From these observations, it was concluded that most young radio pulsars should have a magnetic field between $10^(12)$ and $10^(13)$G. (For comparison, a magnet in a loudspeaker speaker has a field of about 100 gauss.)

In the beginning there was a convection oven

Still, the question remains open: where does the magnetic field come from? Most astronomers assume that it arose at a time when the star had not yet gone supernova. All stars have a weak magnetic field, and it can be strengthened simply as a result of its compression. According to Maxwell's equations of electrodynamics, reducing the size of a magnetized object by half increases the strength of its magnetic field by four times. During the collapse of the core of a massive star, ending with the birth of a neutron star, its size decreases by $10^5$ times, therefore, the magnetic field should increase by $10^(10)$ times.

If the magnetic field of the star's core was strong enough from the start, the core's collapse could explain the pulsar's magnetization. Unfortunately, it is impossible to measure the magnetic field inside a star, so it is impossible to test the hypothesis. In addition, there are quite weighty reasons to believe that the compression of the star is not the only reason for the field enhancement.

As it evolves, the magnetic field changes its shape, generating electrical currents that flow along magnetic field lines outside the star.

In a star, gas can circulate as a result of convection. Hotter regions of ionized gas rise, while colder regions sink. Because ionized gas is a good conductor electricity, penetrating its magnetic lines of force are carried away by the flow of matter. Thus, the field can change and sometimes intensify. It is assumed that it is this phenomenon, known as the dynamo mechanism, that can be the cause of the occurrence of magnetic fields in stars and planets. The dynamo mechanism can operate at any stage in the life of a massive star if its turbulent core rotates fast enough. Moreover, it is during the short period after the transformation of the nucleus into a neutron star that the convection is especially strong.

In 1986, Adam Burrows of the University of Arizona and James M. Lattimer of the State University of New York showed, using computer simulations, that the temperature of a newly formed neutron star exceeded 30 billion degrees. Hot nuclear liquid circulates with a period of 10 ms, possessing huge kinetic energy. Approximately 10 sec. convection dies out.

Shortly after the simulations by Burroughs and Lattimer, Duncan and Thompson, then at Princeton University, assessed the importance of such powerful convection for the formation of a neutron star's magnetic field. The sun can be used as a starting point. When a substance circulates inside it, it drags along the magnetic lines of force, giving the magnetic field about 10% of its kinetic energy. If the moving medium inside the neutron star also converts one tenth of its kinetic energy into a magnetic field, then the field strength should exceed $10^(15)$ G, which is 1000 times greater than the fields of most radio pulsars.

Whether the dynamo will operate in the entire volume of the star or only in its individual regions depends on whether the speed of rotation of the star is comparable with the speed of convection. In the deep layers inside the Sun, these velocities are close, and the magnetic field can "self-organize" on a large scale. Similarly, a newborn neutron star has a rotation period of no more than 10 ms, so superstrong magnetic fields in it can spread widely. In 1992, we named such hypothetical neutron stars magnetars .

The upper limit of the magnetic field strength of a neutron star is about $10^(17)$G. At stronger fields, the matter inside the star begins to mix, and the magnetic field dissipates. In the Universe, we do not know of objects that can generate and maintain magnetic fields that exceed the named limit. One of the side effects of our calculations is the conclusion that radio pulsars are neutron stars in which the large-scale dynamo mechanism did not work. Thus, in the case of the Crab pulsar, a young neutron star rotated with a period of about 20 ms, i.e., much slower than the convection period.

Flickering little magnetar

Although the concept of the magnetar has not yet been developed enough to explain the nature of the SGR, its implications will now become clear to you. The magnetic field should act on the rotation of the magnetar as a strong brake. In 5 thousand years, a $10^(15)$G field will slow down the object's rotation so much that its period will reach 8 seconds, which explains the radiation pulsations observed during the March 1979 burst.

As it evolves, the magnetic field changes its shape, generating electrical currents that flow along magnetic field lines outside the star, which in turn generate X-rays. At the same time, the magnetic field moves through the solid crust of the magnetar, creating bending and tensile stresses in it. It causes heat inner layers stars and sometimes leads to breaks in the crust, accompanied by powerful "starquakes". The electromagnetic energy released during this process creates dense clouds of electrons and positrons, as well as sudden bursts of moderate-strength soft gamma radiation, which gave the name to the periodic SGR sources.

More rarely, the magnetic field becomes unstable and undergoes a large-scale rearrangement. Similar (but smaller) emissions sometimes occur on the Sun, generating solar flares. The magnetar may have enough energy for super-powerful flares like the one observed in March 1979. According to the theory, during the first half second of the giant burst, the expanding plasma ball was the source of radiation. In 1995, we assumed that some of its matter was captured by magnetic lines of force and kept close to the star. This trapped portion gradually contracted and evaporated, continuously emitting X-rays. Based on the amount of energy released, we calculated that a magnetic field of at least $10^(14)$Gs was required to hold this huge plasma ball, which corresponds to the estimate made on the basis of the deceleration rate of the star's rotation.

In 1992, Bohdan Paczinski of Princeton University made an independent assessment of the magnetic field, noting that X-rays can more easily pass through electron clouds if the charged particles are in a strong magnetic field. For the intensity of the X-ray flux in the flare to be so high, the magnetic field induction must have exceeded $10^(14)$G.

EXTREME MAGNETIC FIELDS

MAGNETIC FIELDS confuse radiation and matter

Birefringence of Vacuum
When a polarized light wave (orange line) enters a very strong magnetic field, it changes its speed and hence its wavelength (black lines).

PHOTON SPLITTING
X-ray photons easily split into two or merge with each other. This process is important in fields stronger than $10^(14)$G.

SCATTER SUPPRESSION
A light wave can pass an electron (black dot) almost without disturbance if the magnetic field does not allow it to oscillate and vibrate at the frequency of the wave.

DEFORMATION OF ATOMS
Fields stronger than $10^9$G give the electron orbitals a cigar shape. In a field with an intensity of $10^(14)$G, a hydrogen atom contracts by a factor of 200.

The theory is complicated by the fact that the field strength of the magnetars exceeds the quantum electrodynamic threshold, which is $4\cdot 10^(13)$G. In such strong fields, strange things begin to happen: X-ray photons easily split into two or merge with each other. The vacuum itself is polarized, as a result of which strong birefringence appears in it, as in a calcite crystal. Atoms are deformed, turning into elongated cylinders with a diameter less than the Compton wavelength of an electron (see table). All these strange effects affect the observational manifestations of magnetars. The physics of these phenomena is so unusual that it attracts only a few researchers.

New flash

The researchers continued to monitor the sources of bursts of radiation. The first opportunity came when NASA's Compton Space Gamma Observatory detected a burst of gamma rays in October 1993. This was long awaited by Cuveliota, who joined the Huntsville observatory team. The device that registered the event made it possible to determine the location of the source only with an accuracy of a relatively wide strip of sky. Kuveliotu turned to the Japanese satellite team ASCA for help. Soon Toshio Murakami and his colleagues from the Japanese Institute of Space Science and Astronautics discovered a uniformly emitting X-ray source in the same region of the sky. Then there was another surge, removing all doubt that this object is an SGR. This object was first discovered in 1979, and then it was given the name SGR 1806-20.

In 1995, NASA launched the Rossi X-Ray Timing Explorer (RXTE) satellite, designed to capture changes in X-ray intensity with high precision. With his help, Couveliotou found that the radiation from SGR 1806-20 pulsed with a period of 7.47 seconds, close to the period of 8 seconds observed in the burst of radiation in March 1979 (from the source SGR 0526-66). Over the next five years, the rotation period of the SGR increased by about 0.2%. Although the deceleration rate seems low, it is higher than that of any known radio pulsar, which allows the source's magnetic field to be estimated at $10^(15)$G.

For a more rigorous verification of the magnetar model, one more giant flash was required. In the early morning of August 27, 1998, 19 years after the outbreak that marked the beginning of SGR astronomy, an even more powerful wave of gamma radiation came to Earth from the depths of world space. As a result, the detectors of seven scientific space stations went off scale, and the NASA Comet Asteroid Rendezvous Flyby interplanetary station was forced to go into emergency shutdown mode. Gamma rays hit the night side of the Earth from a source located at the zenith over the middle of the Pacific Ocean.

This early morning, electrical engineer Umran S. Inan and his colleagues at Stanford University were collecting data on the propagation of very low frequency radio waves around the Earth. At 03:22 CET, they detected a sharp change in the ionized upper atmosphere: the lower boundary of the ionosphere dropped from 85 to 60 km in five minutes. This amazing phenomenon was caused by a neutron star in a part of the Galaxy remote from us, separated from the Earth by 20 thousand light years.

Another dynamo

The August 27, 1998 outburst was almost a copy of the March 1979 event. In fact, its energy was ten times less, but since the source was closer to the Earth, the intensity of the gamma-ray burst was much larger than any of the bursts ever recorded, coming from outside the solar system. In the last few hundred seconds of the flash, distinct pulsations were observed with a period of 5.16 seconds. Using the RXTE satellite, Kuveliotu's team measured the star's rate of deceleration. It turned out to be comparable with the deceleration rate of SGR 1806-20, respectively, their magnetic fields are close. Thus, another SGR was added to the list of magnetars. The precise localization of sources in X-rays made it possible to study them with radio and infrared telescopes (but not in visible light, which is strongly absorbed by interstellar dust). Several astronomers have tackled this problem, including Dale Frail of the US National Radio Astronomy Laboratory and Shri Kulkarni of the California Institute of Technology. Other observations have shown that all four confirmed SGRs continue to emit energy, albeit at a weaker rate, between outbursts.

HOW MAGNETAR FLASHES OCCUR

The star's magnetic field is so strong that fractures occasionally occur in the solid crust, releasing huge amounts of energy.

1 Most of the time, the magnetar is calm, but the stresses caused by the magnetic field in its solid crust gradually increase.

2 At a certain moment, the stresses in the crust exceed its tensile strength, and it breaks, probably into many small pieces.

3 This "starquake" generates a pulsating electric current that quickly decays, leaving behind a hot plasma ball.

4 The plasma ball cools by emitting x-rays from its surface. It evaporates within minutes.

Today we can say that the magnetic fields of magnetars are measured more accurately than the magnetic fields of pulsars. In the case of single pulsars, the only evidence that their magnetic fields reach $10^(12)$ G are the measured deceleration rates of their rotation. While the combination of rapid deceleration and bright X-ray flares provides several independent arguments in favor of the fact that the magnetic fields of magnetars range from $10^(14)$ to $10^(15)$G. Alaa Ibrahim and his colleagues at NASA's Goddard Space Flight Center have presented another piece of evidence indicating the strong magnetic fields of magnetars, namely X-ray cyclotron spectral fields, generated, apparently, by protons circulating in a magnetic field with a strength of about $ 10 ^ (15) $Gs.

I wonder if magnetars are associated with any other cosmic phenomena besides SGR? The nature of short gamma-ray bursts has not yet been convincingly explained, but some of them may be due to flashes on magnetars in other galaxies. When observed from very large distances, even a giant flare can be close to the sensitivity limit of the telescope. In this case, it will be possible to fix only a short intense burst of hard gamma radiation, so telescopes will register it as GRB, not SGR.

In the mid 90s. Thompson and Duncan suggested that anomalous X-ray pulsars (AXPs), objects similar in many respects to SGRs, could also be magnetars. But no flares were observed in such pulsars. However, Victoria M. Kaspi and Fotis P. Gavriil of McGill University and Peter M. Woods of the National space research and Tech in Huntsville reported outbreaks in two of the seven known AXPs. One of these objects is associated with the remnants of a young supernova in the constellation Cassiopeia, the other AXP is the first magnetar candidate recorded in visible light. Three years ago it was discovered by Ferdi Hulleman and Martin van Kerkwijk from the University of Utrecht (Netherlands), who were working with Kulkarni. Since then, Brian Kern and Christopher Martin of the California Institute of Technology have observed its brightness in visible light. Its radiation weakens and intensifies with a period equal to the period of pulsations of the X-ray emission of a neutron star. These observations support the idea that this AXP is a magnetar. If it were an ordinary neutron star surrounded by a disk of matter, its visible and infrared radiation would be much more intense, and their pulsations would be much weaker.

The nature of short gamma-ray bursts has not yet been convincingly explained, but some of them may be due to flashes on magnetars in other galaxies.

Recent discoveries and the complete silence of the source of bursts in the Large Magellanic Cloud for 20 years suggest that magnetars can remain dormant for several years and decades, and then suddenly become highly active. Some astronomers believe that AXP is on average younger than SGR, but the question remains open. If both SGR and AXP are magnetars, then they probably make up a significant fraction total number neutron stars.

The history of magnetars is a reminder of how much we still have to learn about the universe. Today we can barely make out a dozen magnetars among the myriad of stars. They manifest themselves only for a fraction of a second in such rays, which register the most complex modern telescopes. For 10 thousand years, their magnetic fields decay, and they cease to emit intense X-rays. Thus, a dozen discovered magnetars indicates the existence of more than a million, and possibly hundreds of millions of them. Old, dark, long-extinct magnetars, like amazing worlds, wander in interstellar space. What secret do we have yet to discover?

ADDITIONALLITERATURE:
Flash! The Hunt for the Biggest Explosions in the Universe. Govert Schilling. Cambridge University Press, 2002.

ABOUT THE AUTHORS:
Chryssa Kouveliotou, Robert C. Duncan, Christopher Thompson have been studying magnetars for a total of 40 years. Kuveliotu is an observer at the National Space Science and Technology Center in Huntsville, Alabama. Among the objects it observes, in addition to repeated soft gamma-ray bursts (SGRs), are "ordinary" gamma-ray bursts and double x-ray systems. Duncan and Thompson are theorists, the former at the University of Texas at Austin and the latter at the Canadian Institute for Theoretical Astrophysics in Toronto. Duncan studies supernovae, quark matter and intergalactic gas clouds. Thompson studied various topics - from cosmic strings before the fall giant meteorites in solar system in the early stages of its existence.

> Magnetars

Find out, what is a magnetar: a description of neutron stars with a powerful magnetic field, a history of research with a photo, a neighbor of the Milky Way, how much energy it emits.

Although the Universe fascinates with its amazing objects, this is far from the friendliest place. It takes about 80-100 years on Earth to kill you. But there is a place where you will die in a split second. So get to know magnetars.

When supermassive stars explode, a neutron star can form in their place. dying heavenly body no longer has enough light pressure to hold gravity. The force is so powerful that protons and electrons are pushed into space, forming neutrons. And what do we have? Neutrons! A solid mass of neutrons.

If a neutron star has formed, then we get . The previously accumulated mass is compressed into a tiny "ball" that rotates a hundred times per second. But that's not the weirdest thing. Of the ten neutron stars that have appeared, there will always be one rather strange one, which is called magnetar. These are neutron stars that came out of supernovae. But in the process of formation, unusual things happen. What exactly? The magnetic field becomes so intense that scientists can't figure out where it's coming from.

Some believe that when the rotation, temperature, and magnetic field of a neutron star converge into a perfect spot, you get a dynamo that amplifies the magnetic field 1,000 times.

But recent discoveries have provided more clues. Scientists have found a magnetar moving away from. We have already been able to observe such objects when one star in the system explodes in the form of a supernova. That is, it was part of the binary system.

During the partnership, the objects orbited side by side (closer to the Earth-Sun distance). This distance was enough to exchange material. The large star began to die first, giving its mass to the smaller one. This caused her to unwind and give the mass back. As a result, the smaller one explodes like a supernova, throwing the second one onto a new trajectory. Instead of forming a neutron star, we got a magnetar.

The power of the observed magnetic field is simply stunning! Near the Earth, it takes 25 gauss, and on the surface we experience only less than 0.5 gauss. A neutron star has a trillion gauss, but magnetars exceed this mark by 1000 times!

What would happen if you were there? Well, within 1,000 km, the magnetic field is strong enough to tear you apart. atomic level. The fact is that the atoms themselves are deformed and can no longer support your shape.

But you would never understand anything, because you died from intense radiation and deadly particles of an object in a magnetic field.

Another uniqueness of magnetars is that they are able to have an earthquake (shaking). It resembles earthly, but takes place on a star. A neutron star has an outer crust that can crack, resembling the movement of Earth's tectonic plates. This is what happens when a magnetar creates an explosion.

The strongest event occurred with the object SGR 1806-20, 50,000 light years distant. In 1/10 of a second, one of the earthquakes created more energy than the Sun in 100,000 years. And this is not a supernova, but just one crack on the surface!

Lucky for us, these really deadly objects are far away and there is no chance that they can get close. To learn more about magnetars and learn more interesting information, watch the video.

magnetars

Astrophysicist Sergei Popov on gamma-ray bursts, strong magnetic fields and X-ray pulsars:

"Hidden" magnetars

Astrophysicist Sergei Popov about magnetars, supernova explosions and the magnetic field of stars: