Supernova - death or the beginning of a new life? Birth and death of supernovae.

Stars don't live forever. They are also born and die. Some of them, like the Sun, exist for several billion years, calmly reach old age, and then slowly fade away. Others live much shorter and more turbulent lives and are also doomed to a catastrophic death. Their existence is interrupted by a giant explosion, and then the star turns into a supernova. The light of a supernova illuminates the cosmos: its explosion is visible at a distance of many billions of light years. Suddenly, a star appears in the sky where, it would seem, there was nothing before. Hence the name. The ancients believed that in such cases a new star really ignites. Today we know that in fact a star is not born, but dies, but the name remains the same, supernova.

SUPERNOVA 1987A

On the night of February 23-24, 1987 in one of the galaxies closest to us. The Large Magellanic Cloud, only 163,000 light-years away, has experienced a supernova in the constellation Dorado. It became visible even to the naked eye, in the month of May it reached a visible magnitude of +3, and in the following months it gradually lost its brightness until it again became invisible without a telescope or binoculars.

Present and past

Supernova 1987A, whose name suggests that it was the first supernova observed in 1987, was also the first visible to the naked eye since the beginning of the era of telescopes. The fact is that the last supernova explosion in our galaxy was observed back in 1604, when the telescope had not yet been invented.

More importantly, star* 1987A gave modern agronomists the first opportunity to observe a supernova at a relatively short distance.

What was there before?

A study of supernova 1987A showed that it belongs to type II. That is, the parent star or progenitor star, which was found in earlier images of this section of the sky, turned out to be a blue supergiant, whose mass was almost 20 times the mass of the Sun. Thus, it was a very hot star that quickly ran out of its nuclear fuel.

The only thing left after a gigantic explosion is a rapidly expanding gas cloud, inside which no one has yet been able to see a neutron star, whose appearance should theoretically be expected. Some astronomers claim that this star is still shrouded in expelled gases, while others have hypothesized that a black hole is forming instead of a star.

LIFE OF A STAR

Stars are born as a result of the gravitational compression of a cloud of interstellar matter, which, when heated, brings its central core to temperatures sufficient to start thermonuclear reactions. The subsequent development of an already lit star depends on two factors: the initial mass and chemical composition, the former, in particular, determining the rate of combustion. Stars with larger mass are hotter and brighter, but that is why they burn out earlier. Thus, the life of a massive star is shorter compared to a star of low mass.

red giants

A star that is burning hydrogen is said to be in its "main phase". Most of the life of any star coincides with this phase. For example, the Sun has been in the main phase for 5 billion years and will remain in it for a long time, and when this period ends, our star will go into a short phase of instability, after which it will stabilize again, this time in the form of a red giant. The red giant is incomparably larger and brighter than the stars in the main phase, but also much colder. Antares in the constellation Scorpio or Betelgeuse in the constellation Orion are prime examples of red giants. Their color can be immediately recognized even with the naked eye.

When the Sun turns into a red giant, its outer layers will "swallow" the planets Mercury and Venus and reach the Earth's orbit. In the red giant phase, stars lose much of their outer layers of atmosphere, and these layers form a planetary nebula like M57, the Ring Nebula in the constellation Lyra, or M27, the Dumbbell Nebula in the constellation Vulpecula. Both are great for observing through your telescope.

Road to the final

From that moment on, the further fate of the star inevitably depends on its mass. If it is less than 1.4 solar masses, then after the end of nuclear combustion, such a star will be freed from its outer layers and will shrink to a white dwarf, the final stage in the evolution of a star with a small mass. Billions of years will pass white dwarf cool down and become invisible. In contrast, a star with a large mass (at least 8 times as massive as the Sun), once it runs out of hydrogen, survives by burning gases heavier than hydrogen, such as helium and carbon. After going through a series of phases of contraction and expansion, such a star, after several million years, experiences a catastrophic supernova explosion, ejecting a huge amount of its own matter into space, and turns into a supernova remnant. For about a week, the supernova outshines all the stars in its galaxy, and then quickly darkens. A neutron star remains in the center, an object small size, which has a gigantic density. If the mass of the star is even greater, as a result of a supernova explosion, not stars, but black holes appear.

TYPES OF SUPERNOVA

By studying the light coming from supernovae, astronomers found out that not all of them are the same and they can be classified depending on the chemical elements present in their spectra. Hydrogen plays a special role here: if there are lines in the spectrum of a supernova that confirm the presence of hydrogen, then it is classified as type II; if there are no such lines, it is assigned to type I. Supernovae of type I are divided into subclasses la, lb and l, taking into account other elements of the spectrum.

Different nature of explosions

The classification of types and subtypes reflects the variety of mechanisms underlying the explosion, and different types precursor stars. Supernova explosions such as SN 1987A come at the last evolutionary stage of a star with a large mass (More than 8 times the mass of the Sun).

Supernovae of the lb and lc types arise as a result of the collapse of the central parts of massive stars that have lost a significant part of their hydrogen envelope due to strong stellar winds or due to the transfer of matter to another star in a binary system.

Various predecessors

All type lb, lc and II supernovae originate from Population I stars, that is, from young stars concentrated in the disks of spiral galaxies. La-type supernovae, in turn, originate from old Population II stars and can be observed in both elliptical galaxies and the cores of spiral galaxies. This type of supernova comes from a white dwarf that is part of a binary system and pulls matter from its neighbor. When the mass of a white dwarf reaches the limit of stability (called the Chandrasekhar limit), a rapid process of fusion of carbon nuclei begins, and an explosion occurs, as a result of which the star throws out most of its mass.

different luminosity

Different classes of supernovae differ from each other not only in their spectrum, but also in the maximum luminosity they achieve in an explosion, and in exactly how this luminosity decreases over time. Type I supernovae tend to be much brighter than Type II supernovae, but they also dim much faster. In Type I supernovae, peak brightness lasts from a few hours to several days, while Type II supernovae can last up to several months. A hypothesis was put forward, according to which stars with a very large mass (several tens of times greater than the mass of the Sun) explode even more violently, like "hypernovae", and their core turns into a black hole.

SUPERNOVA IN HISTORY

Astronomers believe that in our galaxy, on average, one supernova explodes every 100 years. However, the number of supernovae historically documented in the last two millennia is less than 10. One reason for this may be that supernovae, especially type II, explode in spiral arms, where interstellar dust is much denser and, accordingly, can darken the radiance. supernova.

First seen

Although scientists are considering other candidates, today it is generally accepted that the first ever observation of a supernova explosion dates back to 185 AD. It has been documented by Chinese astronomers. In China, explosions of galactic supernovae were also noted in 386 and 393. Then more than 600 years passed, and finally, another supernova appeared in the sky: in 1006, a new star shone in the constellation Wolf, this time recorded, including by Arab and European astronomers. This brightest star (whose apparent magnitude at the peak of brightness reached -7.5) remained visible in the sky for more than a year.
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crab nebula

The supernova of 1054 was also exceptionally bright (maximum magnitude -6), but it was again noticed only by Chinese astronomers, and perhaps even American Indians. This is probably the most famous supernova, since its remnant is the Crab Nebula in the constellation Taurus, which Charles Messier cataloged as number 1.

We also owe Chinese astronomers information about the appearance of a supernova in the constellation Cassiopeia in 1181. Another supernova also exploded there, this time in 1572. This supernova was also noticed by European astronomers, including Tycho Brahe, who described both its appearance and the further change in its brightness in his book On a New Star, whose name gave rise to the term that is used to designate such stars.

Supernova Tycho

32 years later, in 1604, another supernova appeared in the sky. Tycho Brahe passed this information on to his student Johannes Kepler, who began to track the "new star" and dedicated the book "On the New Star in the Leg of Ophiuchus" to her. This star, also observed by Galileo Galilei, remains to date the last of the supernovae visible to the naked eye that exploded in our galaxy.

However, there is no doubt that another supernova has exploded in the Milky Way, again in the constellation Cassiopeia (this record-breaking constellation has three galactic supernovae). Although there is no visual evidence of this event, astronomers found a remnant of the star and calculated that it must match the explosion that occurred in 1667.

Outside the Milky Way, in addition to supernova 1987A, astronomers also observed a second supernova, 1885, which exploded in the Andromeda galaxy.

supernova observation

Hunting for supernovas requires patience and the right method.

The first is necessary, since no one guarantees that you will be able to discover a supernova on the first evening. The second is indispensable if you do not want to waste time and really want to increase your chances of discovering a supernova. The main problem is that it is physically impossible to predict when and where a supernova explosion will occur in one of the distant galaxies. Therefore, a supernova hunter must scan the sky every night, checking dozens of galaxies carefully selected for this purpose.

What do we have to do

One of the most common techniques is to point the telescope at a particular galaxy and compare its appearance with an earlier image (drawing, photograph, digital image), in ideal at approximately the same magnification as the telescope used to observe. If a supernova has appeared there, it will immediately catch your eye. Today, many amateur astronomers have equipment worthy of a professional observatory, such as computer-controlled telescopes and CCD cameras that allow digital photographs of the sky to be taken immediately. But even today, many observers hunt for supernovae simply by pointing their telescope at one galaxy or another and looking through the eyepiece, hoping to see if another star appears somewhere else.

supernova

supernovae- stars ending their evolution in a catastrophic explosive process.

The term "supernovae" was used to describe stars that flared up much (by orders of magnitude) stronger than the so-called "new stars". In fact, neither one nor the other is physically new, already existing stars always flare up. But in several historical cases, those stars that were previously almost or completely invisible in the sky flared up, which created the effect of the appearance of a new star. The type of supernova is determined by the presence of hydrogen lines in the flare spectrum. If it is, then a type II supernova, if not, then a type I supernova.

Physics of supernovae

Type II supernovae

According to modern concepts, thermonuclear fusion eventually leads to the enrichment of the composition of the inner regions of the star with heavy elements. In the process of thermonuclear fusion and the formation of heavy elements, the star contracts, and the temperature in its center rises. (The effect of the negative heat capacity of gravitating non-degenerate matter.) If the mass of the star's core is large enough (from 1.2 to 1.5 solar masses), then the process of thermonuclear fusion reaches its logical conclusion with the formation of iron and nickel nuclei. An iron core begins to form inside the silicon shell. Such a core grows in a day and collapses in less than 1 second once it reaches the Chandrasekhar limit. For the core, this limit is from 1.2 to 1.5 solar masses. Matter falls inside the star, and the repulsion of electrons cannot stop the fall. The central core contracts more and more, and at some point, due to pressure, neutronization reactions begin to take place in it - protons begin to absorb electrons, turning into neutrons. It causes quick loss energy carried away by the resulting neutrinos (the so-called neutrino cooling). The substance continues to accelerate, fall and shrink until the repulsion between the nucleons of the atomic nucleus (protons, neutrons) begins to affect. Strictly speaking, the compression occurs even more than this limit: the falling matter by inertia exceeds the equilibrium point due to the elasticity of the nucleons by 50% ("maximum squeezing"). The process of collapse of the central core is so fast that a rarefaction wave forms around it. Then, following the core, the shell also rushes to the center of the star. After that, the "compressed rubber ball recoils", and the shock wave enters the outer layers of the star at a speed of 30,000 to 50,000 km/s. The outer parts of the star scatter in all directions, and a compact neutron star or black hole remains in the center of the exploded region. This phenomenon is called a type II supernova explosion. These explosions are different in power and other parameters, because. Exploding stars of different masses and different chemical composition. There is evidence that in a type II supernova explosion, much more energy is released than in a type I explosion, because. a proportional part of the energy is absorbed by the shell, but this may not always be the case.

There are a number of ambiguities in the described scenario. In the course of astronomical observations, it was found that massive stars really explode, resulting in the formation of expanding nebulae, and in the center there is a rapidly rotating neutron star emitting regular pulses of radio waves (pulsar). But the theory shows that the outgoing shock wave should split the atoms into nucleons (protons, neutrons). Energy must be spent on this, as a result of which the shock wave must go out. But for some reason this does not happen: in a few seconds, the shock wave reaches the surface of the core, then - the surface of the star and blows away the matter. Several hypotheses for different masses are being considered, but they do not seem convincing. It is possible that in the state of "maximum squeezing" or in the course of the interaction of the shock wave with the substance continuing to fall, some fundamentally new and unknown to us come into force. physical laws. In addition, during the explosion of a supernova with the formation of a black hole, the following questions arise: why the matter after the explosion is not completely absorbed by the black hole; is there an outgoing shock wave and why is it not slowed down and is there something similar to "maximum squeezing"?

Type Ia supernovae

The mechanism of bursts of type Ia (SN Ia) supernovae looks somewhat different. This is the so-called thermonuclear supernova, the explosion mechanism of which is based on the process of thermonuclear fusion in the dense carbon-oxygen core of a star. The precursors of SN Ia are white dwarfs with masses close to the Chandrasekhar limit. It is generally accepted that such stars can form when matter flows from the second component of a binary star system. This happens if the second star of the system goes beyond its Roche lobe or belongs to the class of stars with a superintense stellar wind. As the mass of a white dwarf increases, its density and temperature gradually increase. Finally, when the temperature reaches about 3×10 8 K, conditions arise for thermonuclear ignition of the carbon-oxygen mixture. From the center to the outer layers, the combustion front begins to spread, leaving behind combustion products - the cores of the iron group. The propagation of the combustion front occurs in a slow deflagration regime and is unstable to various types disturbances. Highest value has Rayleigh-Taylor instability, which arises due to the action of the Archimedean force on lighter and less dense combustion products, compared to a dense carbon-oxygen shell. Intensive large-scale convective processes begin, leading to an even greater intensification of thermonuclear reactions and the release of supernova energy (~ 10 51 erg) necessary for the ejection of the shell. The speed of the combustion front increases, turbulence of the flame and the formation of a shock wave in the outer layers of the star are possible.

Other types of supernovae

There are also SN Ib and Ic whose precursors are massive stars in binary systems, in contrast to SN II whose precursors are single stars.

Supernova theory

There is no complete theory of supernovae yet. All proposed models are simplified and have free parameters that must be adjusted to obtain the required explosion pattern. At present, it is impossible to take into account all the physical processes that occur in stars and are important for the development of a flare in numerical models. There is also no complete theory of stellar evolution.

Note that the precursor of the well-known supernova SN 1987A, assigned to the second type, is a blue supergiant, and not a red one, as was assumed before 1987 in SN II models. It is also likely that there is no compact object such as a neutron star or a black hole in its remnant, as can be seen from observations.

The place of supernovae in the universe

According to numerous studies, after the birth of the Universe, it was filled only with light substances - hydrogen and helium. All other chemical elements could be formed only in the process of burning stars. This means that our planet (and you and me) consists of matter formed in the depths of prehistoric stars and thrown out sometime in supernova explosions.

According to scientists, each type II supernova produces an active isotope of aluminum (26Al) about 0.0001 solar masses. The decay of this isotope creates hard radiation, which has been observed for a long time, and it is calculated from its intensity that the abundance of this isotope in the Galaxy is less than three solar masses. This means that type II supernovae should explode in the Galaxy on average twice a century, which is not observed. Probably, in recent centuries, many such explosions were not noticed (occurred behind clouds of cosmic dust). Therefore, most supernovae are observed in other galaxies. Deep Reviews The sky on automatic cameras connected to telescopes now allow astronomers to discover more than 300 flares a year. In any case, it's high time for a supernova to explode...

According to one of the scientists' hypotheses, a cosmic cloud of dust, which appeared as a result of a supernova explosion, can stay in space for about two or three billion years!

supernova observations

To designate supernovae, astronomers use the following system: first, the letters SN are written (from the Latin S uper N ova), then the year of opening, and then with Latin letters is the serial number of the supernova in the year. For example, SN 1997cj denotes a supernova discovered 26 * 3 ( c) + 10 (j) = 88th in a row in 1997.

The most famous supernovas

• Supernova SN 1604 (Kepler's Supernova)
• Supernova G1.9+0.3 (The youngest in our Galaxy)

Historical supernovae in our Galaxy (observed)

see also

Links

• Pskovskiy Yu.P. New and supernovae- a book about new and supernovae stars.
• Tsvetkov D. Yu. Supernova Stars - modern review supernovae.
• Alexey Levin Space Bombs- article in the magazine "Popular Mechanics"
• List of all supernovae observed - List of Supernovae, IAU
• Students for the Exploration and Development of Space -

A supernova is an explosion of dying very large stars with a huge release of energy, a trillion times the energy of the Sun. A supernova can illuminate the entire galaxy, and the light sent by the star will reach the edges of the Universe. If one of these stars explodes at a distance of 10 light years from the Earth, the Earth will completely burn out from energy and radiation emissions.

Supernova

Supernovae not only destroy, they also replenish necessary elements into space: iron, gold, silver and others. Everything we know about the universe was created from the remains of a supernova that once exploded. A supernova is one of the most beautiful and interesting objects in the universe. The largest explosions in the universe leave behind special, strangest remnants in the universe:

neutron stars

Neutron very dangerous and strange bodies. When a giant star goes supernova, its core shrinks to the size of an Earth metropolis. The pressure inside the nucleus is so great that even the atoms inside begin to melt. When the atoms are so compressed that there is no space left between them, enormous energy accumulates and a powerful explosion occurs. After the explosion, an incredibly dense neutron star remains. A teaspoon of a Neutron Star will weigh 90 million tons.

A pulsar is the remains of a supernova explosion. A body that is similar to the mass and density of a neutron star. Rotating at a tremendous speed, pulsars release radiation bursts into space from the north and south poles. The rotation speed can reach 1000 revolutions per second.

When a star 30 times the size of our Sun explodes, it creates a star called Magnetar. Magnetars create powerful magnetic fields they are even stranger than neutron stars and pulsars. The magnetic field of Magnitar exceeds the earth's by several thousand times.

Black holes

After the death of hypernovae, stars even larger than a superstar, the most mysterious and dangerous place the universe is a black hole. After the death of such a star, the black hole begins to absorb its remains. The black hole has too much material to absorb and it throws the remains of the star back into space, forming 2 beams of gamma radiation.

As far as ours is concerned, the Sun certainly doesn't have enough mass to become a black hole, a pulsar, a magnetar, or even a neural star. By cosmic standards, our star is very small for such a finale of her life. Scientists say that after the depletion of fuel, our star will increase in size by several tens of times, which will allow it to absorb the planets of the terrestrial group: Mercury, Venus, Earth and, possibly, Mars.

supernovae- one of the most grandiose cosmic phenomena. In short, a supernova is a real explosion of a star, when most of its mass (and sometimes all) flies apart at a speed of up to 10,000 km / s, and the rest is compressed (collapses) into a superdense neutron star or into black hole. Supernovae play an important role in the evolution of stars. They are the final life of stars with a mass of more than 8-10 solar masses, giving birth to neutron stars and black holes and enriching the interstellar medium with heavy chemical elements. All elements heavier than iron were formed as a result of the interaction of the nuclei of lighter elements and elementary particles in the explosions of massive stars. Isn't here the key to the eternal attraction of mankind to the stars? Indeed, in the smallest cell of living matter there are iron atoms synthesized during the death of some massive star. And in this sense, people are akin to a snowman from Andersen's fairy tale: he had a strange love for a hot stove, because a poker served as a frame for him ...

Scientists have noticed that in elliptical galaxies (i.e., galaxies without a spiral structure, with a very low rate of star formation, consisting mainly of low-mass red stars), only type 1 supernovae flare up. In spiral galaxies, to which our Galaxy belongs - Milky Way, both types of supernovae occur. At the same time, representatives of the 2nd type concentrate towards the spiral arms, where active process star formation and many young massive stars. These features suggest the different nature of the two types of supernovae.

Now it is reliably established that the explosion of any supernova releases a huge amount of energy - about 10 46 J! The main energy of the explosion is carried away not by photons, but by neutrinos - fast particles with a very small or even zero rest mass. Neutrinos interact extremely weakly with matter, and for them the interior of a star is completely transparent.

A complete theory of a supernova explosion with the formation of a compact remnant and ejection of the outer shell has not yet been created due to the extreme complexity of taking into account all the physical processes occurring in this case. However, all evidence suggests that type 2 supernovae flare as a result of the collapse of the cores of massive stars. At different stages of the life of a star, thermonuclear reactions took place in the core, in which first hydrogen turned into helium, then helium into carbon, and so on until the formation of the "iron peak" elements - iron, cobalt and nickel. The atomic nuclei of these elements have the maximum binding energy per particle. It is clear that the addition of new particles to atomic nucleus, for example, iron will require significant energy costs, and therefore thermonuclear combustion “stops” at the elements of the iron peak.

What causes the central parts of the star to lose stability and collapse as soon as the iron core becomes massive enough (about 1.5 solar masses)? Currently, two main factors leading to loss of stability and collapse are known. Firstly, this is the "disintegration" of iron nuclei into 13 alpha particles (helium nuclei) with the absorption of photons - the so-called photodissociation of iron. Secondly, the neutronization of matter is the capture of electrons by protons with the formation of neutrons. Both processes are possible when high densities(over 1 t/cm 3 ), which are established in the center of the star at the end of evolution, and both of them effectively reduce the "elasticity" of the substance, which actually resists the compressive action of gravitational forces. As a result, the core loses its stability and shrinks. In this case, during the neutronization of a substance, a large number of neutrinos carrying away the main energy stored in the collapsing nucleus.

As computer calculations show, the density near the core is so high that even neutrinos that interact weakly with matter are for some time "locked" by the outer layers of the star. But gravitational forces pull the shell towards the core, and a situation arises similar to that which occurs when trying to pour a denser liquid, such as water, over a less dense liquid, such as kerosene or oil. (It is well known from experience that a light liquid tends to "float" from under a heavy one - here the so-called Rayleigh-Taylor instability manifests itself.) This mechanism causes giant convective motions, and when the momentum of the neutrino is eventually transferred to the outer shell, it is dumped into the surrounding space.

Perhaps it is neutrino convective motions that lead to the violation of the spherical symmetry of the supernova explosion. In other words, a direction appears along which the substance is predominantly ejected, and then the resulting residue receives a recoil momentum and begins to move in space by inertia at a speed of up to 1000 km/s. Such high spatial velocities have been noted in young neutron stars - radio pulsars.

The described schematic picture of a type 2 supernova explosion makes it possible to understand the main observational features of this phenomenon. And the theoretical predictions based on this model (especially concerning the total energy and spectrum of a neutrino burst) turned out to be in full agreement with the neutrino pulse registered on February 23, 1987, which came from a supernova in the Large Magellanic Cloud.

Now a few words about type 1 supernovae. The absence of hydrogen emission in their spectra indicates that the explosion occurs in stars devoid of a hydrogen shell. As it is now believed, this may be the explosion of a white dwarf or the result of the collapse of a star. Wolf-Rayet type(in fact, these are the cores of massive stars rich in helium, carbon and oxygen).

How can a white dwarf explode? Indeed, in this very dense star, nuclear reactions do not take place, and the forces of gravity are counteracted by the pressure of a dense gas consisting of electrons and ions (the so-called degenerate electron gas). The reason here is the same as in the collapse of the cores of massive stars - a decrease in the elasticity of the matter of the star with an increase in its density. This is again due to the “pressing” of electrons into protons to form neutrons, as well as some relativistic effects.

Why does the density of a white dwarf increase? This is not possible if it is single. But if a white dwarf is part of a sufficiently close binary system, then under the influence of gravitational forces, gas from a neighboring star is able to flow onto a white dwarf (as in the case of a new star). At the same time, its mass and density will gradually increase, which will eventually lead to collapse and explosion.

Another possible variant more exotic, but no less real, is the collision of two white dwarfs. How can this be, because the probability of two white dwarfs colliding in space is negligible, since the number of stars per unit volume is negligible - at most a few stars in 100 pc3. And here (for the umpteenth time!) Double stars are “guilty”, but now consisting of two white dwarfs.

As follows from general theory Einstein's relativity, any two masses orbiting each other must sooner or later collide due to the constant, albeit very insignificant, entrainment of energy from such a system by gravitational waves - gravitational waves. For example, the Earth and the Sun, if the latter lived infinitely long, would have collided as a result of this effect, though after a colossal time, many orders of magnitude greater than the age of the Universe. It has been calculated that in the case of close binary systems with stellar masses near the solar mass (2 10 30 kg), their merger must occur in the time less than age Universe - in about 10 billion years. Estimates show that in a typical galaxy such events occur once every several hundred years. The gigantic energy released during this catastrophic process is quite enough to explain the supernova phenomenon.

By the way, the approximate equality of the masses of white dwarfs makes their mergers “similar” to each other, which means that type 1 supernovae should look the same in their characteristics, regardless of when and in which galaxy the outbreak occurred. Therefore, the apparent brightness of supernovae reflects the distances to the galaxies in which they are observed. This property of type 1 supernovae is currently used by scientists to obtain an independent estimate of the most important cosmological parameter - the Hubble constant, which serves as a quantitative measure of the expansion rate of the Universe. We have only talked about the most powerful explosions of stars that occur in the Universe and are observed in the optical range. Since in the case of supernovae the main energy of the explosion is carried away by neutrinos, and not by light, the study of the sky by the methods of neutrino astronomy has very interesting prospects. It will allow in the future to "look" into the very "inferno" of a supernova, hidden by huge thicknesses of matter opaque to light. Gravitational-wave astronomy promises even more amazing discoveries, which in the near future will tell us about the grandiose phenomena of the merger of double white dwarfs, neutron stars and black holes.

Explosions of stars, known as supernovae, can be so bright that they outshine the galaxies that contain them.

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Watching the remnants of a supernova that erupted six years ago, astronomers, to their surprise, have identified a new star at the site of the explosion, illuminating the cloud of material surrounding it. The findings of scientists are presented in the journal AstrophysicalJournalletters .

“We have never seen an explosion of this type remain bright for such a long time before, if it did not have any interaction with the hydrogen ejected by the star before the catastrophic event. But there is no signature of hydrogen in the observations of this supernova,” says Dan Milisavlevich, lead author of the study from Purdue University (USA).

Unlike most stellar explosions, which disappear, SN 2012au continues to shine thanks to a powerful newborn pulsar. Credit: NASA, ESA, and J. DePasquale

Explosions of stars, known as supernovae, can be so bright that they outshine the galaxies that contain them. They usually completely "disappear" in a few months or years, but sometimes the remnants of the explosion "collapse" into hydrogen-rich gas clouds and become bright again. But can they shine again without any interference from outside?

As big stars explode, their interiors "roll up" to the point where all particles become neutrons. If the resulting neutron star has a magnetic field and spins fast enough, it can turn into a pulsar wind nebula. This is most likely what happened to SN 2012au, located in the galaxy NGC 4790 in the direction of the constellation Virgo.

“When the pulsar nebula is bright enough, it acts like a light bulb, illuminating the outer ejecta from the previous explosion. We knew that supernovae produced rapidly rotating neutron stars, but never received direct evidence of this unique event,” added Dan Milisavlevich.

An image of the pulsar in Sails taken by NASA's Chandra Observatory. Credit: NASA

SN 2012au initially turned out to be unusual and strange in many ways. Even though the explosion was not bright enough to be classified as a "superluminal" supernova, it was extremely energetic and long-lived.

“If a pulsar is created at the center of the explosion, then it can push out and even accelerate the gas, so in a few years we will be able to see how oxygen-rich gas “runs away” from the SN 2012au explosion,” Dan Milisavlevich explained.

The beating heart of the Crab Nebula. At its center lies a pulsar. Credit: NASA/ESA

Superluminal supernovae are a discussed topic in astronomy. They are potential sources of gravitational waves, as well as gamma-ray bursts and fast radio bursts. But understanding the processes behind these events faces the complexity of observations, and only the next generation of telescopes will help astronomers unravel the mysteries of these flares.