Modeling a supernova birth situation is not an easy task. At least until recently, all experiments failed. But astrophysicists still managed to blow up the star.

November 11, 1572 astronomer Tycho Brahe ( Tycho Brahe) noticed in the constellation Cassiopeia new star, shining as brightly as Jupiter. Perhaps it was then that the confidence that heaven was eternal and unchanging collapsed, and modern astronomy. Four centuries later, astronomers realized that some stars, suddenly becoming billions of times brighter than usual, exploded. In 1934 Fritz Zwicky ( Fritz Zwicky) from California Institute of Technology called them "supernovae". They supply outer space in the Universe with heavy elements that control the formation and evolution of galaxies and help study the expansion of space.

Zwicky and his colleague Walter Baade ( Walter Baade) suggested that gravity provides the energy for the explosion to the star. In their opinion, the star contracts until its central part reaches the density of an atomic nucleus. Collapsing matter can release gravitational potential energy, sufficient to throw out its remains. In 1960 Fred Hoyle ( Fred Hoyle) from Cambridge University and Willie Fowler ( Willy Fowler) from Caltech believed that supernovae are similar to giant nuclear bomb. When a star like the Sun burns its hydrogen and then helium fuel, oxygen and carbon take their turn. The synthesis of these elements not only provides a huge release of energy, but also produces radioactive nickel-56, the decay of which could explain the afterglow of the explosion, which lasts several months.

Both ideas turned out to be correct. Some supernovae have no traces of hydrogen in their spectra (designated Type I); Apparently, most of them had thermonuclear explosion(type I A), and for the rest (types I b and I c) - the collapse of a star that has shed its outer hydrogen layer. Supernovae in which hydrogen (type II) is detected in their spectra also arise as a result of collapse. Both phenomena turn the star into an expanding gas cloud, and gravitational collapse leads to the formation of a super-dense neutron star or even a black hole. Observations, especially of supernova 1987A (Type II), support the proposed theory.

However, a supernova explosion still remains one of the main problems in astrophysics. Computer models have difficulty reproducing it. It's very difficult to make a star explode (which is nice in itself). Stars are self-regulating objects that remain stable over millions and billions of years. Even dying stars have mechanisms of attenuation, but not explosion. To reproduce the latter, it took multidimensional models, the calculation of which was beyond the capabilities of computers.

Explosion is not easy

White dwarfs are the inactive remnants of Sun-like stars that gradually cool and fade. They can explode as Type I supernovae a. However, according to Hoyle and Fowler, if a white dwarf orbits another star in a close orbit, it can accrete (suck) material from its companion, thereby increasing its mass, central density and temperature to such an extent that explosive fusion from carbon is possible and oxygen.

Thermonuclear reactions should behave like ordinary fire. The combustion front can propagate through the star, leaving behind “nuclear ash” (mostly nickel). At each moment of time, fusion reactions must occur in a small volume, mainly in a thin layer on the surface of bubbles filled with “ash” and floating in the depths of the white dwarf. Because of their low density, bubbles can float to the star's surface.

But the thermonuclear flame will go out as the release of energy causes the star to expand and cool, extinguishing its combustion. Unlike a conventional bomb, the star does not have an envelope limiting its volume.

In addition, it is impossible to recreate a supernova explosion in a laboratory; it can only be observed in space. Our team carried out rigorous simulations using a supercomputer IBM p690. The numerical model of the star was represented by a computational grid with 1024 elements on each side, which made it possible to resolve details several kilometers in size. Each computational set required more than 10 20 arithmetic operations; Only a supercomputer could cope with such a task, performing more than 10 11 operations per second. In the end, all this took almost 60 processor-years. Various computational tricks that simplify the model and are used in other fields of science are not applicable to supernovae with their asymmetric flows, extreme conditions and a gigantic spatial and temperature range. Particle Physics, nuclear physics, hydrodynamics and relativity are very complex, and supernova models must operate with them simultaneously.

Under the hood

The solution came from an unexpected direction - while studying the operation of a car engine. Mixing gasoline and oxygen and their ignition creates turbulence, which, in turn, increases the combustion surface, intensively deforming it. In this case, the rate of fuel combustion, proportional to the combustion area, increases. But a star is also turbulent. Gas flows pass through it huge distances With high speed, therefore the slightest disturbances quickly turn a calm flow into a turbulent flow. In a supernova, the rising hot bubbles must mix the matter, causing the nuclear combustion to spread so quickly that the star does not have time to rearrange itself and “extinguish” the flame.

In a properly running engine internal combustion the flame propagates at a subsonic speed, limited by the rate of heat diffusion through the substance - this process is called deflagration, or rapid combustion. In a "shooting" engine, the flame spreads with supersonic speed in the form shock wave, rushing through the oxygen-fuel mixture and compressing it (detonation). A thermonuclear flame can also spread in two ways. Detonation can completely burn a star, leaving only the most “non-flammable” elements, such as nickel and iron. However, in the products of these explosions, astronomers find a wide variety of elements, including silicon, sulfur and calcium. Consequently, nuclear combustion propagates, at least initially, as deflagration.

IN recent years reliable models of thermonuclear deflagration were created. Researchers from the University of California (Santa Cruz), the University of Chicago, and our group relied on programs created for the study chemical combustion and even for weather forecasts. Turbulence is a fundamentally three-dimensional process. In a turbulent cascade, kinetic energy is redistributed from large to small scales and is ultimately dissipated as heat. The original stream is split into smaller and smaller parts. Therefore, modeling must necessarily be three-dimensional.

The supernova model has a mushroom-like appearance: hot bubbles rise in a layered environment, wrinkled and stretched by turbulence. The increase in the rate of nuclear reactions, enhanced by it, in a few seconds leads to the destruction of the white dwarf, the remains of which fly away at a speed of about 10 thousand km/s, which corresponds to the observed picture.

But it is still not clear why a white dwarf ignites. In addition, deflagration should eject most of the dwarf's material unchanged, and observations indicate that only a small part of the star is unchanged. The explosion is likely caused not only by rapid combustion, but also by detonation, and the cause of type I supernovae a- not only the accretion of matter onto a white dwarf, but also the merger of two white dwarfs.

Gravity grave

Another type of supernova, caused by the collapse of a stellar core, is more difficult to explain. From an observational point of view, these supernovae are more diverse than thermonuclear ones: some have hydrogen, others do not; some explode in the dense interstellar medium, others in almost empty space; some release huge amounts of radioactive nickel, others do not. The ejection energy and expansion rate also vary. The most powerful of them produce not only a classic supernova explosion, but also a long-lasting gamma-ray burst (see: N. Gehrels, P. Leonard and L. Piro. The brightest explosions in the Universe // VMN, No. 4, 2003). This heterogeneity of properties is one of many mysteries. Core collapse supernovae are prime candidates for the formation of the heaviest elements, such as gold, lead, thorium and uranium, which can only form in special conditions. But no one knows whether such conditions actually arise in a star when its core explodes.

Although the idea of ​​collapse seems simple (compressing the core releases gravitational binding energy, which ejects the outer layers of matter), it is difficult to understand the process in detail. At the end of its life, a star with a mass of more than 10 solar masses develops a layered structure; layers of increasingly heavier elements appear with depth. The core is composed primarily of iron, and the star's equilibrium is maintained by the quantum repulsion of electrons. But eventually the mass of the star suppresses the electrons, which are squeezed into atomic nuclei, where they begin to react with protons and form neutrons and electron neutrinos. In turn, the neutrons and remaining protons are pressed closer together until their own repulsive force takes effect and stops the collapse.

At this moment, the compression stops and is replaced by expansion. The matter, pulled in deep by gravity, begins to partially flow out. In classical theory this task is solved using a shock wave, which occurs when the outer layers of a star collide at supersonic speeds with a core that has suddenly slowed down its compression. The shock wave moves outward, compressing and heating the material it hits, while at the same time losing its energy, eventually dying out. Simulations show that the compression energy dissipates quickly. How, then, does a star explode itself?

The first attempt to solve the problem was the work of Stirling Colgate ( Stirling Colgate) and Richard White ( Richard White) 1966, and later computer models by Jim Wilson ( Jim Wilson), created by him in the early 1980s, when all three worked at the Lawrence Livermore National Laboratory. Lawrence. They suggested that the shock wave is not the only carrier of energy from the core to the outer layers of the star. It is possible that neutrinos produced during the collapse play a supporting role. At first glance, the idea looks strange: as we know, neutrinos are extremely inactive, they interact so weakly with other particles that they are even difficult to register. But in a collapsing star they have more than enough energy to cause an explosion, and in conditions of extremely high density they interact well with matter. Neutrinos heat the layer around the collapsing supernova core, maintaining pressure in the decelerating shock wave.

Core collapse supernova

1. Supernovae of another kind are formed when stars with masses greater than 8 solar masses collapse. They belong to Type I b, I c or II, depending on observed features
2. A massive star at the end of its life has a layered structure of different chemical elements
3. Iron does not participate in nuclear fusion, so no heat is generated in the core. Gas pressure drops, and the material lying above rushes down
4. In a second, the core contracts and turns into a neutron star. Falling matter bounces off a neutron star and creates a shock wave
5. Neutrinos burst out of a newborn neutron star, pushing an irregular shock wave outward
6. A shock wave sweeps through the star, tearing it apart

Like a rocket

But is this extra push enough to sustain the wave and complete the explosion? Computer simulation showed that it was not enough. Despite the fact that the gas both absorbs neutrinos and emits them; the models showed that losses dominate, and therefore the explosion fails. But in these models there was one simplification: the star in them was considered spherically symmetrical. Therefore, high-dimensional phenomena such as convection and rotation were ignored, which are very important because the observed supernovae produce a very non-spherical, “shaggy” remnant.

Multidimensional modeling shows that neutrinos heat up the plasma around the supernova core and create bubbles and mushroom-shaped flows in it. Convection transfers energy to the shock waves, pushing them upward and causing an explosion.

When the blast wave slows down slightly, the bubbles of hot, expanding plasma, separated by the cold material flowing down, merge. One or more bubbles gradually form surrounded by downdrafts. As a result, the explosion becomes asymmetrical. In addition, the decelerated shock wave can be deformed, and then the collapse takes the form hourglass. Additional instability occurs when the shock wave breaks out and passes through the heterogeneous layers of the supernova ancestor. In this case, the chemical elements synthesized during the life of the star and during the explosion are mixed.

Because the remnants of the star mostly fly out in one direction, the central neutron star bounces off in the other, like a skateboard rolling back when you jump off it. Our computer model shows a rebound velocity of more than 1000 km/s, consistent with the observed motion of many neutron stars. But some of them move more slowly, probably because the bubbles did not have time to merge during the explosion that formed them. A single picture emerges, in which the different variations result from one main effect.

Despite significant achievements in recent years, none of the existing models reproduces the entire complex of phenomena associated with a supernova explosion and contains simplifications. Full version must use seven dimensions: space (three coordinates), time, neutrino energy and neutrino speed (described by two angular coordinates). Moreover, this must be done for all three types, or flavors, of neutrinos.

But can an explosion be triggered by various mechanisms? After all, a magnetic field can intercept rotational energy newly formed neutron star and give new push shock wave. In addition, it will squeeze matter outward along the rotation axis in the form of two polar jets. These effects will help explain the most powerful explosions. In particular, gamma-ray bursts can be associated with jets moving at near-light speed. Perhaps the cores of such supernovae collapse not into a neutron star, but into a black hole.

While theorists are improving their models, observers are trying to use not only electromagnetic radiation, but also neutrinos and gravitational waves. The collapse of the star's core, its seething at the beginning of the explosion and its possible transformation into a black hole lead not only to an intense emission of neutrinos, but also shake the structure of space-time. Unlike light, which cannot penetrate the layers above, these signals come directly from the seething inferno at the center of the explosion. Newly developed neutrino detectors and gravitational waves can lift the curtain on the mystery of the death of stars.

Supernova reaction effect

Observers have wondered why neutron stars are rushing across the Galaxy at great speed. New core collapse supernova models offer an explanation based on the internal asymmetry of these explosions

Modeling shows that asymmetry develops already at the beginning of the explosion. Small differences in the onset of stellar collapse lead to large differences in the degree of asymmetry

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 catastrophic death. Their existence is interrupted by a giant explosion, and then the star turns into a supernova. The light of a supernova illuminates space: its explosion is visible at a distance of many billions of light years. Suddenly a star appears in the sky where before, it would seem, there was nothing. Hence the name. The ancients believed that in such cases a new star actually lights up. 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. In the Large Magellanic Cloud, only 163,000 light years away, a supernova appeared in the constellation Doradus. It became visible even to the naked eye, in May it reached visible magnitude +3, and in subsequent months it gradually lost its brightness until it again became invisible without a telescope or binoculars.

Present and past

Supernova 1987A, as its name suggests, was the first supernova observed in 1987 and the first to be visible to the naked eye since the dawn of the telescope era. The fact is that the last supernova explosion in our Galaxy was observed back in 1604, when the telescope had not yet been invented.

But 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 was a Type II supernova. That is, the progenitor star or predecessor star, which was discovered in earlier photographs of this part 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 the gigantic explosion was a rapidly expanding gas cloud, inside which no one had yet been able to discern a neutron star, whose appearance theoretically should have been expected. Some astronomers argue that the star is still shrouded in released 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 gravitational compression of a cloud of interstellar matter, which, when heated, brings its central core to temperatures sufficient to initiate thermonuclear reactions. The subsequent development of an already ignited star depends on two factors: the initial mass and chemical composition, the first, in particular, determining the combustion rate. Stars with larger masses are hotter and lighter, but that's why they burn out earlier. Thus, the life of a massive star is shorter compared to a low-mass star.

Red giants

A star that burns hydrogen is said to be in its “primary 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 there 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 cooler. Antares in the constellation Scorpio or Betelgeuse in the constellation Orion - vivid examples 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 “absorb” the planets Mercury and Venus and reach the Earth’s orbit. In the red giant phase, stars lose a significant part of the outer layers of their 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 viewing through your telescope.

Road to the final

From this 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 of the evolution of a star with no large mass. It will take billions of years for the white dwarf to cool down and become invisible. In contrast, a high-mass star (at least 8 times more massive than the Sun), once it runs out of hydrogen, survives by burning gases heavier than hydrogen, such as helium and carbon. Having gone through a series of phases of compression and expansion, such a star after several million years experiences a catastrophic supernova explosion, ejecting a gigantic amount of its own matter into space, and turns into a supernova remnant. Within about a week, the supernova exceeds the brightness of all the stars in its galaxy, and then quickly darkens. A neutron star remains in the center, a small object with a gigantic density. If the mass of the star is even greater, as a result of the supernova explosion, not stars, but black holes appear.

TYPES OF SUPERNOVA

By studying the light coming from supernovae, astronomers have found that they are not all the same and can be classified depending on the chemical elements represented in their spectra. Special role hydrogen plays here: if the spectrum of a supernova contains lines confirming the presence of hydrogen, then it is classified as type II; if there are no such lines, it is classified as type I. Type I supernovae 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 the different types of progenitor stars. Supernova explosions such as SN 1987A occur in the last evolutionary stage of a star with a large mass (more than 8 times the mass of the Sun).

Type lb and lc supernovae arise from the collapse of the central parts of massive stars that have lost a significant part of their hydrogen shell due to strong stellar winds or due to the transfer of matter to another star in dual system.

Various predecessors

All supernovae of types lb, lc and II originate from Population I stars, that is, from young stars concentrated in the disks of spiral galaxies. Type la 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 is pulling material from its neighbor. When the mass of a white dwarf reaches its stability limit (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 the explosion, and in how exactly this luminosity decreases over time. Type I supernovae are generally much brighter than Type II supernovae, but they also dim much faster. Type I supernovae last for a few hours to a few days at peak brightness, 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 the mass of the Sun) explode even more violently, like “hypernovas,” and their core turns into a black hole.

SUPERNOVES IN HISTORY

Astronomers believe that on average one supernova explodes in our Galaxy every 100 years. However, the number of supernovae historically documented in the last two millennia does not reach even 10. One reason for this may be due to the fact that supernovae, especially type II, explode in spiral arms, where interstellar dust is much denser and, accordingly, can dim the glow supernova.

The first one I saw

Although scientists are considering other candidates, today it is generally accepted that the first observation of a supernova explosion in history dates back to 185 AD. It was documented by Chinese astronomers. In China, galactic supernova explosions were also observed 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, among other things, by Arab and European astronomers. This brightest luminary(whose apparent value at its peak 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 again it was noticed only by Chinese astronomers, and perhaps also by American Indians. This is probably the most famous supernova, since its remnant is the Crab Nebula in the constellation Taurus, which Charles Messier included in his catalog under number 1.

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

Supernova Quiet

32 years later, in 1604, another supernova appeared in the sky. Tycho Brahe passed this information on to his student Johannes Kepler, who began tracking the “new star” and dedicated the book “On the New Star at the Foot of Ophiuchus” to it. This star, also observed by Galileo Galilei, remains today the last supernova visible to the naked eye to explode in our Galaxy.

However, there is no doubt that another supernova has exploded in the Milky Way, again in the constellation Cassiopeia (the constellation that holds the record for three galactic supernovae). Although there is no visual evidence of this event, astronomers have found a remnant of the star and calculate that it must correspond to an 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 supernovae 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 very first evening. You can't do without the second one if you don't 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. So a supernova hunter must scan the sky every night, checking dozens of galaxies carefully selected for this purpose.

What to do

One of the most common techniques is to point a telescope at a particular galaxy and compare its appearance with an earlier image (drawing, photograph, digital image), V ideal with approximately the same magnification as the telescope with which the observations are made. If a supernova 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 them to take photographs of the starry sky directly in digital format. But even today, many observers hunt for supernovae by simply pointing a telescope at a particular galaxy and looking through the eyepiece, hoping to see if another star appears somewhere.

Required equipment

Supernova hunting doesn't require overly sophisticated equipment. Of course, you need to consider the power of your telescope. The fact is that each instrument has a limiting magnitude, which depends on various factors, and the most important of them is the diameter of the lens (however, the brightness of the sky is also important, depending on light pollution: the smaller it is, the higher the limiting value). With your telescope, you can look at hundreds of galaxies looking for supernovae. However, before you begin observing, it is very important to have on hand celestial maps to identify galaxies, as well as drawings and photographs of the galaxies you plan to observe (there are dozens of resources on the Internet for supernova hunters), and finally, an observation log where you will record data for each observation session.

Night difficulties

The more supernova hunters there are, the greater the chances of noticing their appearance immediately at the moment of explosion, which makes it possible to track their entire light curve. From this point of view, amateur astronomers provide extremely valuable assistance to professionals.

Supernova hunters must be prepared to endure the cold and humidity of the night. In addition, they will have to fight sleepiness (a thermos with hot coffee is always included in the basic equipment of lovers of night astronomical observations). But sooner or later their patience will be rewarded!

One of the important achievements of the 20th century was the understanding of the fact that almost all elements heavier than hydrogen and helium are formed in the interiors of stars and enter the interstellar medium as a result of supernova explosions, one of the most powerful phenomena in the Universe.

Photo: Blazing stars and wisps of gas provide a breathtaking backdrop to the self-destruction of a massive star called Supernova 1987A. Astronomers observed its explosion in Southern Hemisphere February 23, 1987. This Hubble image shows supernova remnants surrounded by inner and outer rings of material in diffuse clouds of gas. This three-color image is a composite of several photographs of the supernova and its surrounding region that were taken in September 1994, February 1996, and July 1997. Numerous bright blue stars near the supernova are massive stars, each about 12 million years old and 6 times heavier than the Sun. They all belong to the same generation of stars as the one that exploded. The presence of bright gas clouds is another sign of the youth of this region, which is still fertile ground for the birth of new stars.

Initially, all stars whose brightness suddenly increased by more than 1,000 times were called new. When flaring, such stars suddenly appeared in the sky, disrupting the usual configuration of the constellation, and increased their brightness to the maximum, several thousand times, then their brightness began to fall sharply, and after a few years they became as faint as they were before the flare. The repetition of flares, during each of which the star ejects up to one thousandth of its mass at high speed, is characteristic of new stars. And yet, despite the grandeur of the phenomenon of such a flare, it is not associated either with a fundamental change in the structure of the star, or with its destruction.

Over five thousand years, information has been preserved about more than 200 bright flares of stars, if we limit ourselves to those that did not exceed the 3rd magnitude in brightness. But when the extragalactic nature of the nebulae was established, it became clear that the new stars flaring up in them were superior in their characteristics to ordinary novae, since their luminosity often turned out to be equal to the luminosity of the entire galaxy in which they flared up. The unusual nature of such phenomena led astronomers to the idea that such events were something completely different from ordinary novae, and therefore in 1934, at the suggestion of American astronomers Fritz Zwicky and Walter Baade, those stars whose flares at maximum brilliance reached the luminosities of normal galaxies were identified into a separate, brightest in luminosity and rare class of supernovae.

Unlike outbursts of ordinary novae, supernova outbursts in the current state of our Galaxy are extremely rare phenomena, occurring no more often than once every 100 years. The most striking outbreaks were in 1006 and 1054; information about them is contained in Chinese and Japanese treatises. In 1572, the outbreak of such a star in the constellation Cassiopeia was observed by the outstanding astronomer Tycho Brahe, and the last person to monitor the supernova phenomenon in the constellation Ophiuchus in 1604 was Johannes Kepler. During the four centuries of the “telescopic” era in astronomy, such flares have not been observed in our Galaxy. The position of the Solar System in it is such that we are optically able to observe supernova explosions in approximately half of its volume, and in the rest of its volume the brightness of the outbreaks is dimmed by interstellar absorption. V.I. Krasovsky and I.S. Shklovsky calculated that supernova explosions in our Galaxy occur on average once every 100 years. In other galaxies, these processes occur with approximately the same frequency, so the main information about supernovae in the optical burst stage was obtained from observations of them in other galaxies.

Realizing the importance of studying such powerful phenomena, astronomers W. Baade and F. Zwicky, working at the Palomar Observatory in the USA, began a systematic systematic search for supernovae in 1936. They had at their disposal a telescope of the Schmidt system, which made it possible to photograph areas of several tens of square degrees and gave very clear images of even faint stars and galaxies. Over three years, they discovered 12 supernova explosions in different galaxies, which were then studied using photometry and spectroscopy. As observational technology improved, the number of newly discovered supernovae steadily increased, and the subsequent introduction of automated searches led to an avalanche-like increase in the number of discoveries (more than 100 supernovae per year at total number 1,500). In recent years, large telescopes have also begun searching for very distant and faint supernovae, since their studies can provide answers to many questions about the structure and fate of the entire Universe. In one night of observations with such telescopes, more than 10 distant supernovae can be discovered.

As a result of the explosion of a star, which is observed as a supernova phenomenon, a nebula is formed around it, expanding at enormous speed (about 10,000 km/s). A high expansion rate is the main feature by which supernova remnants are distinguished from other nebulae. In supernova remnants, everything speaks of an explosion of enormous power, which scattered the outer layers of the star and imparted enormous speeds to individual pieces of the ejected shell.

Crab Nebula

Not a single space object has given astronomers so much valuable information as the relatively small Crab Nebula, observed in the constellation Taurus and consisting of diffuse gaseous matter flying away at high speed. This nebula, a remnant of a supernova observed in 1054, became the first galactic object with which a radio source was identified. It turned out that the nature of radio emission has nothing in common with thermal emission: its intensity systematically increases with wavelength. Soon it was possible to explain the nature of this phenomenon. The supernova remnant must have a strong magnetic field that holds what it created. cosmic rays(electrons, positrons, atomic nuclei) having speeds close to the speed of light. In a magnetic field, they emit electromagnetic energy in a narrow beam in the direction of movement. The discovery of non-thermal radio emission from the Crab Nebula prompted astronomers to search for supernova remnants using this very feature.

The nebula located in the constellation Cassiopeia turned out to be a particularly powerful source of radio emission; at meter waves, the flux of radio emission from it is 10 times higher than the flux from the Crab Nebula, although it is much further than the latter. In optical rays, this rapidly expanding nebula is very weak. The Cassiopeia nebula is believed to be the remnant of a supernova explosion that took place about 300 years ago.

A system of filament nebulae in the constellation Cygnus also showed radio emission characteristic of old supernova remnants. Radio astronomy has helped identify many other non-thermal radio sources that turned out to be supernova remnants. of different ages. Thus, it was concluded that the remnants of supernova explosions that occurred even tens of thousands of years ago stand out among other nebulae for their powerful non-thermal radio emission.

As already mentioned, the Crab Nebula was the first object from which X-ray emission was discovered. In 1964, it was discovered that the source of X-ray radiation emanating from it is extended, although its angular dimensions are 5 times smaller angular dimensions the Crab Nebula itself. From which it was concluded that X-ray radiation is emitted not by a star that once erupted as a supernova, but by the nebula itself.

Supernova influence

On February 23, 1987, a supernova exploded in our neighboring galaxy, the Large Magellanic Cloud, which became extremely important for astronomers because it was the first that they, armed with modern astronomical instruments, could study in detail. And this star confirmed a whole series of predictions. Simultaneously with the optical flare, special detectors installed in Japan and Ohio (USA) detected a flux of neutrinos - elementary particles born at very high temperatures during the collapse of the star's core and easily penetrating through its shell. These observations confirmed an earlier suggestion that about 10% of the mass of a collapsing star's core is emitted as neutrinos as the core itself collapses into a neutron star. In very massive stars, during a supernova explosion, the cores are compressed to even greater densities and probably turn into black holes, but the outer layers of the star are still shed. In recent years, there have been indications of a connection between some cosmic gamma-ray bursts and supernovae. It is possible that the nature of cosmic gamma-ray bursts is related to the nature of explosions.

Supernova explosions have a strong and diverse impact on the surrounding interstellar medium. The supernova envelope, ejected at enormous speed, scoops up and compresses the gas surrounding it, which can give impetus to the formation of new stars from the clouds of gas. A team of astronomers led by Dr. John Hughes (Rutgers University), using observations from the orbiting Chandra X-ray Observatory (NASA), made important discovery, which sheds light on how supernova explosions create silicon, iron and other elements. An X-ray image of supernova remnant Cassiopeia A (Cas A) reveals clumps of silicon, sulfur and iron ejected from the star's interior during the explosion.

The high quality, clarity and information content of the images of the Cas A supernova remnant obtained by the Chandra Observatory allowed astronomers not only to determine chemical composition many nodes of this residue, but also to find out exactly where these nodes were formed. For example, the most compact and brightest nodes are composed primarily of silicon and sulfur with very little iron. This indicates that they formed deep inside the star, where temperatures reached three billion degrees during the collapse that ended in a supernova explosion. In other nodes, astronomers discovered very great content iron with admixtures of some silicon and sulfur. This substance formed even deeper in those parts where the temperature during the explosion reached more than high values four to five billion degrees. A comparison of the locations of both the silicon-rich bright and fainter iron-rich nodes in the Cas A supernova remnant revealed that the “iron” features, originating from the deepest layers of the star, are located at the outer edges of the remnant. This means that the explosion threw the “iron” nodes further than all the others. And even now they appear to be moving away from the center of the explosion at greater speed. Studying the data obtained by Chandra will allow us to settle on one of several mechanisms proposed by theorists that explain the nature of the supernova explosion, the dynamics of the process and the origin of new elements.

SN I supernovae have very similar spectra (without hydrogen lines) and light curve shapes, while SN II spectra contain bright hydrogen lines and are characterized by diversity in both spectra and light curves. In this form, the classification of supernovae existed until the mid-80s of the last century. And with the beginning of the widespread use of CCD receivers, the quantity and quality of observational material increased significantly, which made it possible to obtain spectrograms for previously inaccessible faint objects, to determine the intensity and width of lines with much greater accuracy, and also to register weaker lines in spectra. As a result, the seemingly established binary classification of supernovae began to quickly change and become more complex.

Supernovae also differ according to the types of galaxies in which they explode. IN spiral galaxies supernovae of both types explode, but in elliptical ones, where there is almost no interstellar medium and the star formation process has ended, only supernovae of type SN I are observed, obviously, before the explosion - these are very old stars, whose masses are close to the solar one. And since the spectra and light curves of supernovae of this type are very similar, it means that the same stars explode in spiral galaxies. The natural end of the evolutionary path of stars with masses close to the Sun is the transformation into a white dwarf with the simultaneous formation of a planetary nebula. A white dwarf contains almost no hydrogen, since it is the end product of the evolution of a normal star.

Every year, several planetary nebulae are formed in our Galaxy, therefore, most stars of this mass quietly complete their life path, and only once every hundred years does an SN type I supernova burst. What reasons determine a completely special ending, not similar to the fate of other similar stars? The famous Indian astrophysicist S. Chandrasekhar showed that if a white dwarf has a mass less than about 1.4 solar masses, it will quietly “live out” its life. But if it is in a sufficiently close binary system, its powerful gravity is capable of “pulling” matter from the companion star, which leads to a gradual increase in mass, and when it passes the permissible limit powerful explosion, leading to the death of the star.

SN II supernovae are clearly associated with young, massive stars, in the shells of which hydrogen is present in large quantities. Outbursts of this type of supernova are considered the final stage of the evolution of stars with an initial mass of more than 8 x 10 solar masses. In general, the evolution of such stars proceeds quite quickly - in a few million years they burn their hydrogen, then helium turns into carbon, and then the carbon atoms begin to transform into atoms with higher atomic numbers.

In nature, transformations of elements with a large release of energy end with iron, whose nuclei are the most stable, and energy release does not occur during their fusion. Thus, when the core of a star becomes iron, the release of energy in it stops, it can no longer resist gravitational forces, and therefore begins to quickly shrink, or collapse.

The processes occurring during collapse are still far from being fully understood. However, it is known that if all the matter in the core turns into neutrons, then it can resist the forces of attraction - the core of the star turns into a “neutron star”, and the collapse stops. In this case, enormous energy is released, entering the shell of the star and causing expansion, which we see as a supernova explosion.

This is to be expected genetic connection between supernova explosions and the formation of neutron stars and black holes. If the evolution of the star had previously occurred “quietly,” then its envelope should have a radius hundreds of times greater than the radius of the Sun, and also retain a sufficient amount of hydrogen to explain the spectrum of SN II supernovae.

Supernovae and pulsars

The fact that after a supernova explosion, in addition to the expanding shell and various types of radiation, other objects remain, it became known in 1968 due to the fact that a year earlier radio astronomers had discovered pulsars - radio sources whose radiation is concentrated in individual pulses repeated after a strictly defined period of time. Scientists were amazed by the strict periodicity of the pulses and the shortness of their periods. The greatest attention was attracted by the pulsar, the coordinates of which were close to the coordinates of a nebula very interesting for astronomers, located in southern constellation Parusov, which is considered to be the remnant of a supernova explosion - its period was only 0.089 seconds. And after the discovery of a pulsar in the center of the Crab Nebula (its period was 1/30 of a second), it became clear that pulsars are somehow related to supernova explosions. In January 1969, a pulsar from the Crab Nebula was identified with a faint star of 16th magnitude, changing its brightness with the same period, and in 1977 it was possible to identify a pulsar in the constellation Velae with the star.

The periodicity of pulsar radiation is related to their fast rotation, but not a single ordinary star, not even a white dwarf, could rotate with the period characteristic of pulsars; it would be immediately torn apart by centrifugal forces, and only a neutron star, very dense and compact, could withstand them. As a result of analyzing many options, scientists came to the conclusion that supernova explosions are accompanied by the formation of neutron stars - a qualitatively new type of object, the existence of which was predicted by the theory of the evolution of high-mass stars.

Supernovae and black holes

The first evidence of a direct connection between a supernova explosion and the formation of a black hole was obtained by Spanish astronomers. A study of the radiation emitted by a star orbiting a black hole in the binary system Nova Scorpii 1994 found that it contains large amounts of oxygen, magnesium, silicon and sulfur. There is an assumption that these elements were captured by it when a neighboring star, having survived a supernova explosion, turned into a black hole.

Supernovae (especially Type Ia supernovae) are among the brightest star-shaped objects in the Universe, so even the most distant of them can be studied using currently available equipment. Many Type Ia supernovae have been discovered in relatively nearby galaxies. Sufficiently accurate estimates of the distances to these galaxies made it possible to determine the luminosity of supernovae exploding in them. If we assume that distant supernovae have the same luminosity on average, then the distance to them can be estimated from the observed magnitude at maximum brightness. Comparing the distance to the supernova with the receding speed (red shift) of the galaxy in which it exploded makes it possible to determine the main quantity characterizing the expansion of the Universe - the so-called Hubble constant.

Even 10 years ago, values ​​were obtained for it that differed by almost two times - from 55 to 100 km/s Mpc, but today the accuracy has been significantly increased, as a result of which the value 72 km/s Mpc is accepted (with an error of about 10%) . For distant supernovae, whose redshift is close to 1, the relationship between distance and redshift also allows us to determine quantities that depend on the density of matter in the Universe. According to Einstein's general theory of relativity, it is the density of matter that determines the curvature of space, and therefore future fate Universe. Namely: will it expand indefinitely or will this process ever stop and be replaced by compression. Recent studies of supernovae have shown that most likely the density of matter in the Universe is insufficient to stop the expansion, and it will continue. And in order to confirm this conclusion, new observations of supernovae are needed.

Supernova or supernova explosion- a phenomenon during which a star sharply changes its brightness by 4-8 orders of magnitude (a dozen magnitudes) followed by a relatively slow attenuation of the flare. It is the result of a cataclysmic process that occurs at the end of the evolution of some stars and is accompanied by the release of enormous energy.

As a rule, supernovae are observed after the fact, that is, when the event has already occurred and its radiation has reached the Earth. Therefore, the nature of supernovae was unclear for a long time. But now quite a lot of scenarios are proposed that lead to outbreaks of this kind, although the main provisions are already quite clear.

The explosion is accompanied by the ejection of a significant mass of matter from the outer shell of the star into interstellar space, and from the remaining part of the matter from the core of the exploded star, as a rule, a compact object is formed - a neutron star, if the mass of the star before the explosion was more than 8 solar masses (M ☉), or a black star a hole with a star mass over 20 M ☉ (the mass of the core remaining after the explosion is over 5 M ☉). Together they form a supernova remnant.

A comprehensive study of previously obtained spectra and light curves in combination with the study of remnants and possible progenitor stars makes it possible to build more detailed models and study the conditions that existed at the time of the outburst.

Among other things, the material ejected during the flare largely contains products of thermonuclear fusion that occurred throughout the life of the star. It is thanks to supernovae that the Universe as a whole and each galaxy in particular chemically evolves.

The name reflects historical process studying stars whose brightness changes significantly over time, the so-called novae.

The name is made up of the label SN, followed by the year of opening, followed by a one- or two-letter designation. The first 26 supernovae of the current year receive single-letter designations, at the end of the name, from capital letters from A to Z. The remaining supernovae receive two-letter designations from lowercase letters: aa, ab, and so on. Unconfirmed supernovae are designated by letters PSN(eng. possible supernova) with celestial coordinates in the format: Jhhmmssss+ddmmsss.

The big picture

Light curves

The light curves for type I are highly similar: there is a sharp increase for 2-3 days, then it is replaced by a significant drop (by 3 magnitudes) for 25-40 days, followed by a slow weakening, almost linear on the magnitude scale. The average absolute magnitude of the maximum for Ia flares is M B = − 19.5 m (\textstyle M_(B)=-19.5^(m)), for Ib\c - .

But the light curves of type II are quite varied. For some, the curves resembled those for type I, only with a slower and longer decline in brightness until the linear stage began. Others, having reached a peak, stayed at it for up to 100 days, and then the brightness dropped sharply and reached a linear “tail.” The absolute magnitude of the maximum varies widely from − 20 m (\textstyle -20^(m)) to − 13 m (\textstyle -13^(m)). Average value for IIp - M B = − 18 m (\textstyle M_(B)=-18^(m)), for II-L M B = − 17 m (\textstyle M_(B)=-17^(m)).

Spectra

The above classification already contains some basic features of the spectra of supernovae of various types; let us dwell on what is not included. The first and very important feature, which for a long time prevented the decoding of the obtained spectra - the main lines are very broad.

The spectra of type II and Ib\c supernovae are characterized by:

• The presence of narrow absorption features near the brightness maximum and narrow undisplaced emission components.
• Lines , , , observed in ultraviolet radiation.

Observations outside the optical range

Flash rate

The frequency of flares depends on the number of stars in the galaxy or, which is the same for ordinary galaxies, luminosity. A generally accepted quantity characterizing the frequency of flares in different types of galaxies is SNu:

1 S N u = 1 S N 10 10 L ⊙ (B) ∗ 100 y e a r (\displaystyle 1SNu=(\frac (1SN)(10^(10)L_(\odot )(B)*100year))),

Where L ⊙ (B) (\textstyle L_(\odot )(B))- luminosity of the Sun in filter B. For different types of flares its value is:

In this case, supernovae Ib/c and II gravitate toward spiral arms.

Observing supernova remnants

The canonical scheme of the young remainder is as follows:

1. Possible compact remainder; usually a pulsar, but possibly a black hole
2. External shock wave propagating in interstellar matter.
3. A return wave propagating in the supernova ejecta material.
4. Secondary, spreading in clots interstellar medium and in dense supernova emissions.

Together they form the following picture: behind the front of the external shock wave, the gas is heated to temperatures T S ≥ 10 7 K and emits in the X-ray range with a photon energy of 0.1-20 keV; similarly, the gas behind the front of the return wave forms a second region of X-ray radiation. Lines of highly ionized Fe, Si, S, etc. indicate the thermal nature of the radiation from both layers.

Optical radiation from the young remnant creates gas in clumps behind the front of the secondary wave. Since the propagation speed in them is higher, which means the gas cools faster and the radiation passes from the X-ray range to the optical range. The impact origin of the optical radiation is confirmed by the relative intensity of the lines.

Theoretical description

Decomposition of observations

The nature of supernovae Ia is different from the nature of other outbreaks. This is clearly evidenced by the absence of type Ib\c and type II flares in elliptical galaxies. From general information it is known about the latter that there is little gas and blue stars there, and star formation ended 10 10 years ago. This means that all massive stars have already completed their evolution, and only stars with a mass less than solar mass remain, and no more. From the theory of stellar evolution it is known that stars of this type cannot be exploded, and therefore a life extension mechanism is needed for stars with masses of 1-2M ⊙.

The absence of hydrogen lines in the Ia\Iax spectra indicates that there is extremely little hydrogen in the atmosphere of the original star. The mass of the ejected substance is quite large - 1M ⊙, mainly containing carbon, oxygen and other heavy elements. And the shifted Si II lines indicate that nuclear reactions are actively occurring during the ejection. All this convinces that the predecessor star is a white dwarf, most likely carbon-oxygen.

The attraction to the spiral arms of type Ib\c and type II supernovae indicates that the progenitor star is short-lived O-stars with a mass of 8-10M ⊙ .

Thermonuclear explosion

One of the ways to release the required amount of energy is a sharp increase in the mass of the substance involved in thermonuclear combustion, that is, a thermonuclear explosion. However, the physics of single stars does not allow this. Processes in stars located on the main sequence are in equilibrium. Therefore, all models consider the final stage stellar evolution- white dwarfs. However, the latter itself is a stable star, and everything can change only when approaching the Chandrasekhar limit. This leads to the unambiguous conclusion that a thermonuclear explosion is possible only in multiple star systems, most likely in the so-called double stars.

In this scheme, there are two variables that affect the state, chemical composition and final mass of the substance involved in the explosion.

• The second companion is an ordinary star, from which matter flows to the first.
• The second companion is the same white dwarf. This scenario is called double degeneracy.

• An explosion occurs when the Chandrasekhar limit is exceeded.
• The explosion occurs before him.

What all supernova Ia scenarios have in common is that the exploding dwarf is most likely carbon-oxygen. In the explosive combustion wave traveling from the center to the surface, the following reactions occur:

The mass of the reacting substance determines the energy of the explosion and, accordingly, the maximum brightness. If we assume that the entire mass of the white dwarf reacts, then the energy of the explosion will be 2.2 10 51 erg.

The further behavior of the light curve is mainly determined by the decay chain:

The isotope 56 Ni is unstable and has a half-life of 6.1 days. Next e-capture leads to the formation of a 56 Co nucleus predominantly in an excited state with an energy of 1.72 MeV. This level is unstable, and the transition of the electron to the ground state is accompanied by the emission of a cascade of γ quanta with energies from 0.163 MeV to 1.56 MeV. These quanta experience Compton scattering, and their energy quickly decreases to ~100 keV. Such quanta are already effectively absorbed by the photoelectric effect, and, as a result, heat the substance. As the star expands, the density of matter in the star decreases, the number of photon collisions decreases, and the material on the star's surface becomes transparent to radiation. As theoretical calculations show, this situation occurs approximately 20-30 days after the star reaches its maximum luminosity.

60 days after the onset, the substance becomes transparent to γ-radiation. The light curve begins to decay exponentially. By this time, the 56 Ni isotope has already decayed, and the energy release is due to the β-decay of 56 Co to 56 Fe (T 1/2 = 77 days) with excitation energies up to 4.2 MeV.

Gravitational core collapse

The second scenario for the release of the necessary energy is the collapse of the star's core. Its mass should be exactly equal to the mass of its remnant - a neutron star, substituting typical values ​​we get:

where M = 0, and R = 10 km, G is the gravitational constant. The characteristic time for this is:

where ρ 12 is the density of the star, normalized to 10 12 g/cm 3 .

The obtained value is two orders of magnitude greater than kinetic energy shells. A carrier is needed that, on the one hand, must carry away the released energy, and on the other, not interact with the substance. Neutrinos are suitable for the role of such a carrier.

Several processes are responsible for their formation. The first and most important for the destabilization of a star and the beginning of contraction is the process of neutronization:

3 H e + e − → 3 H + ν e (\displaystyle ()^(3)He+e^(-)\to ()^(3)H+\nu _(e))

4 H e + e − → 3 H + n + ν e (\displaystyle ()^(4)He+e^(-)\to ()^(3)H+n+\nu _(e))

56 F e + e − → 56 M n + ν e (\displaystyle ()^(56)Fe+e^(-)\to ()^(56)Mn+\nu _(e))

Neutrinos from these reactions carry away 10%. The main role in cooling is played by URKA processes (neutrino cooling):

E + + n → ν ~ e + p (\displaystyle e^(+)+n\to (\tilde (\nu ))_(e)+p)

E − + p → ν e + n (\displaystyle e^(-)+p\to \nu _(e)+n)

Instead of protons and neutrons, atomic nuclei can also act, forming unstable isotope, which undergoes beta decay:

E − + (A , Z) → (A , Z − 1) + ν e , (\displaystyle e^(-)+(A,Z)\to (A,Z-1)+\nu _(e) ,)

(A , Z − 1) → (A , Z) + e − + ν ~ e . (\displaystyle (A,Z-1)\to (A,Z)+e^(-)+(\tilde (\nu ))_(e).)

The intensity of these processes increases with compression, thereby accelerating it. This process is stopped by the scattering of neutrinos on degenerate electrons, during which they are thermolyzed and locked inside the substance. A sufficient concentration of degenerate electrons is achieved at densities ρ n u c = 2, 8 ⋅ 10 14 (\textstyle \rho _(nuc)=2,8\cdot 10^(14)) g/cm 3 .

Note that neutronization processes occur only at densities of 10 11 /cm 3, achievable only in the stellar core. This means that hydrodynamic equilibrium is disturbed only in it. The outer layers are in local hydrodynamic equilibrium, and the collapse begins only after the central core contracts and forms hard surface. The rebound from this surface ensures the release of the shell.

Model of a young supernova remnant

Supernova remnant evolution theory

There are three stages in the evolution of the supernova remnant:

The expansion of the shell stops at the moment when the pressure of the gas in the remnant equals the pressure of the gas in the interstellar medium. After this, the residue begins to dissipate, colliding with chaotically moving clouds. Resorption time reaches:

T m a x = 7 E 51 0.32 n 0 0.34 P ~ 0 , 4 − 0.7 (\displaystyle t_(max)=7E_(51)^(0.32)n_(0)^(0.34)(\tilde (P))_( 0.4)^(-0.7)) years

Theory of the occurrence of synchrotron radiation

Construction of a detailed description

Search for supernova remnants

Search for precursor stars

Supernova Ia theory

In addition to the uncertainties in the supernova Ia theories described above, the mechanism of the explosion itself has been a source of much controversy. Most often, models can be divided into the following groups:

• Instant detonation
• Delayed detonation
• Pulsating delayed detonation
• Turbulent fast combustion

At least for every combination initial conditions The listed mechanisms can be found in one variation or another. But the range of proposed models is not limited to this. An example is a model where two white dwarfs detonate at once. Naturally, this is only possible in scenarios where both components have evolved.

Chemical evolution and impact on the interstellar medium

Chemical evolution of the Universe. Origin of elements with atomic number higher than iron

Supernova explosions are the main source of replenishment of the interstellar medium with elements with atomic numbers greater (or as they say heavier) He . However, the processes that gave rise to them for various groups elements and even their own isotopes.

R process

r-process is the process of the formation of heavier nuclei from lighter ones through the sequential capture of neutrons during ( n,γ) reactions and continues until the rate of neutron capture is higher than the rate of β− decay of the isotope. In other words, the average time of capture of n neutrons τ(n,γ) should be:

where τ β is the average time of β-decay of nuclei forming a chain of the r-process. This condition imposes a limitation on the neutron density, because:

Where (σ n γ , v n) ¯ (\displaystyle (\overline ((\sigma _(n\gamma),v_(n)))))- product of the reaction cross section ( n,γ) on the neutron velocity relative to the target nucleus, averaged over the Maxwellian spectrum of the velocity distribution. Considering that the r-process occurs in heavy and medium nuclei, 0.1 s< τ β < 100 с, то для n ~ 10 и температуры среды T = 10 9 , получим характерную плотность

Such conditions are achieved in:

ν-process

Main article: ν-process

ν-process is a process of nucleosynthesis through the interaction of neutrinos with atomic nuclei. It may be responsible for the appearance of the isotopes 7 Li, 11 B, 19 F, 138 La and 180 Ta

Impact on the large-scale structure of the galaxy's interstellar gas

Observation history

Hipparchus's interest in the fixed stars may have been inspired by the observation of a supernova (according to Pliny). Earliest record identified as supernova SN 185 (English), was made by Chinese astronomers in 185 AD. The brightest known supernova, SN 1006, has been described in detail by Chinese and Arab astronomers. The supernova SN 1054, which gave birth to the Crab Nebula, was well observed. Supernovae SN 1572 and SN 1604 were visible naked eye and had great value in the development of astronomy in Europe, as they were used as an argument against the Aristotelian idea that the world beyond the Moon and the Solar system is unchanged. Johannes Kepler began observing SN 1604 on October 17, 1604. This was the second supernova that was recorded at the stage of increasing brightness (after SN 1572, observed by Tycho Brahe in the constellation Cassiopeia).

With the development of telescopes, it became possible to observe supernovae in other galaxies, starting with observations of the supernova S Andromeda in the Andromeda Nebula in 1885. During the twentieth century, successful models for each type of supernova and understanding of their role in star formation has increased. In 1941, American astronomers Rudolf Minkowski and Fritz Zwicky developed a modern classification scheme for supernovae.

In the 1960s, astronomers discovered that the maximum luminosity of supernova explosions could be used as a standard candle, hence an indicator astronomical distances. Supernovae now provide important information about cosmological distances. The most distant supernovae turned out to be fainter than expected, which, according to modern ideas, shows that the expansion of the Universe is accelerating.

Methods have been developed to reconstruct the history of supernova explosions that have no written observational records. The date of supernova Cassiopeia A was determined from the light echo from the nebula, while the age of supernova remnant RX J0852.0-4622 (English) estimated by measuring temperature and γ emissions from the decay of titanium-44. In 2009 in Antarctic ice nitrates were discovered corresponding to the timing of the supernova explosion.

On February 23, 1987, supernova SN 1987A, the closest to Earth observed since the invention of the telescope, erupted in the Large Magellanic Cloud at a distance of 168 thousand light years from Earth. For the first time, the neutrino flux from the flare was recorded. The flare was intensively studied using astronomical satellites in the ultraviolet, X-ray and gamma-ray ranges. The supernova remnant was studied using ALMA, Hubble and Chandra. Neither a neutron star nor a black hole, which, according to some models, should be located at the site of the flare, have yet been discovered.

January 22, 2014 in the M82 galaxy, located in the constellation Big Dipper, the supernova SN 2014J erupted. Galaxy M82 is located 12 million light-years from our galaxy and has an apparent magnitude of just under 9. This supernova is the closest to Earth since 1987 (SN 1987A).

The most famous supernovae and their remnants

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

Historical supernovae in our Galaxy (observed)

It is quite rare that people can observe such an interesting phenomenon as a supernova. But this is not an ordinary birth of a star, because up to ten stars are born in our galaxy every year. A supernova is a phenomenon that can only be observed once every hundred years. The stars die so brightly and beautifully.

To understand why a supernova explosion occurs, we need to go back to the very birth of the star. Hydrogen flies in space, which gradually gathers into clouds. When the cloud is large enough, condensed hydrogen begins to accumulate in its center, and the temperature gradually rises. Under the influence of gravity, the core of the future star is assembled, where, thanks to increased temperature and increasing gravity, the thermonuclear fusion reaction begins to take place. How much hydrogen a star can attract to itself determines its future size - from a red dwarf to a blue giant. Over time, the balance of the star's work is established, the outer layers put pressure on the core, and the core expands due to the energy of thermonuclear fusion.

The star is unique and, like any reactor, someday it will run out of fuel - hydrogen. But for us to see how a supernova explodes, a little more time must pass, because in the reactor, instead of hydrogen, another fuel (helium) was formed, which the star will begin to burn, turning it into oxygen, and then into carbon. And this will continue until iron is formed in the core of the star, which, when thermonuclear reaction does not release energy, but consumes it. Under such conditions, a supernova explosion can occur.

The core becomes heavier and colder, causing the lighter upper layers to fall onto it. Fusion starts again, but this time faster than usual, as a result of which the star simply explodes, scattering its matter into the surrounding space. Depending on the known ones may also remain after it - (a substance with an incredibly high density, which is very high and can emit light). Such formations remain after very big stars, which were able to produce thermonuclear fusion to very heavy elements. Smaller stars leave behind neutron or iron small stars, which emit almost no light, but also have a high density of matter.

Novas and supernovae are closely related, because the death of one of them can mean the birth of a new one. This process continues endlessly. A supernova carries millions of tons of matter into the surrounding space, which again gathers into clouds, and the formation of a new one begins celestial body. Scientists say that everything heavy elements, which are located in our Solar system, the Sun “stole” during its birth from a star that once exploded. Nature is amazing, and the death of one thing always means the birth of something new. IN outer space matter decays and is formed in stars, creating the great balance of the Universe.