About seven thousand years ago in a remote corner of outer space suddenly exploded star, throwing off the outer layers of matter. Relatively large and massive star is suddenly faced with a serious energy problem - its physical integrity was under threat. When was passed stability boundary, broke into a fascinating, highly powerful, one of the most disastrous in the Universe explosions that produced a supernova. Six thousand years raced on the expanses of space light from this star in the constellation of Taurus and finally reached the Earth.

It happened in g. In Europe science was then immersed in slumber, and the Arabs she experienced a period of stagnation, but in another part of the Earth observers noted object, magnificent, glittering in the sky before sunrise. Fourth of July g. Chinese astronomers, gazing into heaven, and saw the glowing object in the sky, which was a lot brighter than Venus. It was observed in Beijing and Kaifeng and was called"the star-guest". It was the most powerful after the Sun object in the sky. For 23 days, until July 27 g., it was visible even during the day. Gradually, the object has become weaker, but still visible to the naked eye even 627 days and finally disappeared on 17 April g. It was the brightest of all registered supernova - it shone as 500 million Suns. If she found us at a distance, as our nearest star, alpha Centauri, the darkest of nights by its light we could freely read the newspaper - Shine much brighter than the full Moon.

In the European Chronicles of those years there is no mention this event, but we should not forget that those were the years of the middle ages, when on the European continent almost extinguished the light of science. One interesting point in the history of the discovery of this star. In 1955. William Miller and Helmut ABT from observatories mount Wilson and mount Palomar discovered prehistoric icons on the wall of one of the cave in the cliff of the canyon, Navajo nation in Arizona. In the canyon of the image was carved in stone, and in the cave drawn piece of hematite - red iron. Both figures show the circle and the Crescent. Miller interpret these figures as images of the moon sickle and the stars; in his opinion, they may indicate the emergence of a supernova in g. To such conclusion there are two reasons: first, in g., when erupted supernova, phase of the moon and its location relative to the supernova were exactly as shown. Secondly, found in those places clay shards found that about a thousand years ago in this area was inhabited by Indians. Thus, drawings, apparently, is an artistic image of a supernova, made by the ancient Indians.

After shooting and thorough research of the sky, where there was a supernova, it was found that the remains of the supernova form a complex chaotic expanding gaseous envelope containing several stars. The whole complex of gas and stars was named the crab nebula. The source of the substance of the nebula is one of the Central star, the one that exploded seven thousand years ago. It is a neutron star. It has a temperature of 6-7 million To extremely small diameter. Photographs and the spectrograms, you can determine the physical characteristics of stars. The study revealed that the crab nebula are two types of radiating fields. First, it fibrous grid consisting of a gas heated to tens of thousands of degrees and ionized by intense ultraviolet radiation from the Central star; gas includes hydrogen, helium, oxygen, neon, sulphur. And secondly, the large luminous amorphous region, against which we see gas fiber. The photographs, made about twelve years ago, I found that some of the fibers of the nebula are moving from its center to the outside. Knowing the angular size, and also about the distance and the speed of expansion, scientists have determined that about nine years ago on the place of the nebula was a point source. Thus was able to establish a direct link between the crab nebula, the supernova explosion, which is almost a thousand years ago was observed by Chinese and Japanese astronomers.

The question about the reasons of explosions of supernovas is still a matter of debate and is the cause for the nomination of contradictory hypotheses. A star with a mass exceeding that of the sun by about 20%, may eventually become unsustainable. It showed in his brilliant theoretical study, done at the end of 30-ies of our century, the astronomer the Chandrasekhar. He found that such stars on the side of life sometimes catastrophically changes, which results in a certain state of equilibrium, allowing the star adequately complete their way of life. Many astronomers studied the latter stages of stellar evolution and investigate the dependence of the evolution of stars from its mass. They all come to the same conclusion: if the mass of the star exceeds the Chandrasekhar limit, its expect incredible changes. As we have seen, the stability of a star is determined by the ratio between the forces of gravity, seeking to squeeze the star, and by pressure, extending it from the inside. We also know that in the last stages of stellar evolution, when are depleted nuclear fuel, this ratio is maintained due to the effect of degeneration, which can lead star to stage a white dwarf and allow her to spend my life in this condition. Becoming a white dwarf star gradually cools down and ends his life, becoming cold, lifeless, invisible star slag.

If the mass of the star exceeds the Chandrasekhar limit, the effect of the degeneration is already unable to provide the required ratio of pressures. Before the star remains only one way for balance - maintain a high temperature. But this requires an internal source of energy. In the ordinary course of evolution of the star gradually uses of nuclear fuel. But how can a star to produce energy in the final stages of stellar evolution, when nuclear fuel, regularly supplying energy at the end ? Of course it is not the energy "bankrupt", it's big, massive object, a significant portion of the mass of which is at a great distance from the center, and she still have a gravitational energy. It is like a rock sitting on the top of a high mountain, and due to its location with potential energy. The energy contained in the outer layers of the star, as found in huge pantry, from which at the right time it can be retrieved. So, in order to maintain the pressure, the star now begins to shrink, thus adding to the stock of his inner energy.

How long does this compression? Fred Hoyle and his colleagues examined carefully the situation and came to the conclusion that in fact is a catastrophic contraction followed by a catastrophic explosion. The impetus explosion, relieving the star from excess weight, is the density, created under compression. Getting rid of excess weight, the star returns immediately on the way to the ordinary extinction. The greatest interest for scientists is the process in which step by step is a gradual fading of nuclear fuel. For calculation of this process uses the information obtained from laboratory experiments; great is the role of modern fast computing machines. Hoyle and Fowler modeled by computer, the process of energy release in the star and followed its course. As an example, they took the star, whose weight three times exceeds the sun, that is, a star, far beyond the Chandrasekhar limit. Star with such weighing must have the luminosity, 60 times the luminosity of the Sun, and the lifetime of about 600 million years.

We already know that in the normal course of thermonuclear reactions in the interior of stars almost throughout her life, hydrogen is converted into helium. After a considerable part of the substance of the star turns into helium temperature in the center increases. If temperatures rise to around $ 200 million To the nuclear fuel becomes helium, which is then converted into oxygen and neon. Thus, helium nucleus begins to produce heavier nucleus consisting of two chemical elements. Now, the star becomes a multilayer energoproektami system. In the thin shell, on one side of which is hydrogen, but on the other helium, is the conversion of hydrogen into helium; this reaction is emitting energy. Therefore, until the reaction is carried out, the core temperature of the star is steadily growing. Compression stars leads to seal its nucleus and a rise in temperature in the center of 200-300 million To. But even with such high temperatures, oxygen and neon quite stable and not become a nuclear reaction. However, after some time the kernel gets even tighter temperature doubles, she is now is equal to 600 million K. And then nuclear fuel becomes neon, which during the reaction is transformed and magnesium and silicon. Education magnesium accompanied by the release of free neutrons. When a star is born of the matriarchs, she already had some metals of the iron group. Free neutrons, reacting with these metals, create more atoms of heavy metals - up to uranium, the heaviest natural elements. But spent the whole neon in the kernel.

The core begins to shrink, and again compression accompanied by a rise in temperature. The next step, when every two atoms of oxygen, when combined, produce silicon atom and helium atom. Atoms creamtion, connecting pairs to form atoms of Nickel that soon become the iron atoms. In a nuclear reaction, accompanied by the emergence of new chemical elements, will come not only neutrons, but also protons and helium atoms. Appear elements such as sulfur, aluminum, calcium, argon, phosphorus, chlorine, potassium. The core temperature rises up to half a billion degrees. She is still in the formation of heavier elements with the use of free neutrons, but at this stage because of the large temperature happen some new phenomena. Hoyle believes that at temperatures of about a billion degrees occurs powerful gamma radiation that can destroy the nuclei of atoms. Neutrons and protons are detached from the nuclei, but the process is reversible as particle again unite, creating a stable combination. When the temperature exceeds 1.5 billion To more than likely become the processes of decay of nuclei. Curious and unexpected was the following: at the further increase of temperature and the strengthening of processes of destruction and connections kernel eventually attach more and more particles and, as a consequence, there heavier chemical elements. So, at the temperature of 2-5 billion To be born titanium, vanadium, chrome, iron, cobalt, zinc, etc. But all of these elements presents the most iron. As before, when the transformation of light elements in heavy produce energy holding a star from collapsing. Its internal structure of a star now reminds onion, each layer of which is filled mainly to any one item.

According to Hoyle, with the formation of a group of iron star is on the eve of the dramatic explosion. Nuclear reactions occurring in the iron core of the star, lead to the conversion of protons into neutrons. Thus emitted flows neutrinos, carrying away with him into space considerable amount of energy star. If the temperature in the core of a star great, these energy losses can have serious consequences, as they lead to an easing of pressures radiation required to maintain the sustainability of the stars. As a consequence, the action again come gravitational forces, designed to deliver the necessary energy star. The gravity is faster squeeze the star to replenish the energy that is carried away neutrinos. As before compression stars accompanied by a rise in temperature, which eventually reaches 4-5 billion OK, Now things are a bit different. The core consisting of elements of the iron group undergoes serious changes: members of this group are not already come into reaction with the formation of heavier elements, and begin again to turn into helium, emitting thus enormous flow of neutrons. Most of these neutrons captured the substance of the outer layers of the star and participates in the creation of heavy elements. At this stage, as indicated by Hoyle, the star reaches a critical state. When was created the heavy chemical elements, the energy released by the merger of light nuclei. Thus, a huge number of star allocated for hundreds of millions of years. Now the final products of nuclear reactions again decay generating helium: the star may be forced to replace lost earlier energy. Remains of the last of its asset - gravity. But the star could use this provision, the density of its core should grow very quickly, that is, the kernel has sharply shrunk; is "explosion inside", separating the core of a star from its outer layers. It should happen within a few seconds. This is the beginning of the end of a massive star.

Implosion or explosion inside, eliminates the pressure that supported the outer layers of the star, its shell, and from that moment the shell, compressed, begins to fall into the nucleus. The decline is accompanied by release enormous amounts of energy - so once again manifests itself gravity. The release of energy in turn leads to a sharp increase of temperature (approximately 3 billion To ), and falling shell of the star is in the unusual temperature conditions. For stars with the core temperature is equal to 2.5 billion To light shell elements provide a potential nuclear fuel. But to ensure the glow during the explosion, the temperature should rise above this value to 3 billion K. during the second kinetic energy star is converted into heat, and the substance of the shell is heated. At such high temperatures lighter elements - mostly oxygen - exhibit explosive instability and begin to interact. It is estimated that over time is less than seconds during these nuclear reactions is the energy equal to the energy that the Sun radiates over a billion years !

Suddenly the liberated energy tears from the star, its outer layers and throws them into space with the speed of up to several thousand kilometers per second. These layers form a significant part of the mass of the star. Gas shell is removed from a star-forming nebula, which stretches for many millions of millions of kilometers. Gas inertia continues moving from the stars up until, perhaps 100,000 years, the substance of the nebula is so sparse and diffuse that no longer will be able to get excited by short-wave radiation of very hot parent star, then we will cease to see him. But the most important thing: how exploded in substance and in neizvestnom gas is present magnetic field. The compression of gas behind the shock wave front is caused by reduction of power lines and increase of tension of the interstellar magnetic field, which in turn leads to an increase in electron energy, and their acceleration. The result is a superhot star, the weight of which reduced it so that it could adequately to fade and die. In all probability, it will become a neutron star with a mass of 1.2-2 the mass of the Sun. If its mass is more than twice the mass of the Sun, it eventually may turn into a black hole. A supernova is a very rare objects. The history has witnessed only a few cases of occurrence of a supernova. The first is, of course, the crab nebula, the second Supernova Tycho Brahe found in g..and the third Kepler's Supernova, open them in 1604 Recently became aware of a supernova in the constellation Lupus. Astronomers have calculated that each star system, the galaxy, on average, once in a hundred or three hundred years gives birth of a supernova. Currently, astronomers have discovered about 150 supernova.

Only three of them were in our Galaxy, although there are many objects, such as a Loop in Swan and Cassiopeia A, which, as you suggest, may be the remnants of supernova explosions of the milky Way.

The exact time of the explosion in Cygnus Loop is almost impossible to install, but I believe that if this is indeed the remains of a supernova explosion, a Loop in Swan began its expansion of about 60 thousand years ago. Cassiopeia a is the youngest supernova in the sky, as its expansion began in 1700. Why nature creates such strange objects ? How do they arise ? What is the mechanism of outbreaks, which by their brightness can compete with the brilliance of tens of billions of stars ? What is the end product of a stellar explosion ? This is only part of the issues that arise in an astronomer, watching the greatest explosions in a particular area of the sky. To answer at least some of them, it is necessary to investigate the history of the life of a star. Professor John A. Wheeler said: "it is One thing to study almost stationary star, such as the Sun, and another thing - when we predict bizarre dynamics of a supernova. We know in detail to predict and running of nuclear reactions going on in the bowels of the Sun and other stars, and the energy output radiation from the surface of the star. However, can we with the same confidence to speak about the stars, which is experiencing strong internal movement ?" Recently, scientists have attempted to apply mathematical coiriu nuclear explosion for describing the hydrodynamics of a supernova. This allowed to carefully examine the hydrodynamics of a supernova with the help of the theory, which is certainly not too far from the truth. Some astronomers distinguish between five types of supernovae; two of them main is a supernova of type 1 and supernovae of type 2. They differ from each other by the luminosity, the nature of the change luminosities, spectra, and also the number and location of a particular galaxy or in various types of galaxies. The nature of changes in luminosity over time supernova both basic types are almost the same.