If the mass of the star in two times more than the sun, by the end of his life, the star may explode as a supernova, but if the mass of the matter remained after the explosion, still exceeds two sun, the star should be compressed into a tiny tight body, since the gravitational force is entirely suppress any internal resistance to compression. Scientists believe it is at this point catastrophic gravitational collapse leads to the emergence of a black hole. They believe that with the end of thermonuclear reactions star can no longer be in stable condition. Then for a massive star remains one of the inevitable path is the path of universal and full compression (collapse), turning it into the invisible black hole.

In the year 1939. R. Oppenheimer and his graduate student Snyder at the University of California (Berkeley) was in the final clarification of the fate of a large mass of cold matter. One of the most striking consequence of the General theory of relativity was the following: when a large mass begins to collapsibility, this process cannot be stopped and weight is compressed into a black hole. If, for example, non-symmetric star begins to collapse to a critical size, known as the gravitational radius, or the Schwarzschild radius (named after Karl Schwarzschild, which was the first to point to its existence). If the star reaches this radius, then nothing can stop her from complete collapse, that is, to withdraw into themselves. What is equal to a gravitational radius ? Simple mathematical equation shows that the body mass of the Sun's gravitational radius is equal to almost 3 km, while for a system that includes a billion stars, galaxies - this radius is equal to the distance from the Sun to the orbit of the planet Uranus, that is 3 billion km

What are the physical properties "black holes" and as scientists expect to detect these objects ? Many scientists were thinking on these issues; received some of the answers that can help in the search for such objects.

The name itself - black holes shows that this class of objects that cannot be seen. The gravitational field is so strong that if some way managed to be near a black hole and send away from the surface of the beam of the most powerful projector to see the spotlight would be impossible even from a distance not greater than the distance from the earth to the Sun. Indeed, even if we were able to concentrate all the light of the Sun in this powerful spotlight, we would not have seen him as the light would not be able to overcome the influence of the gravitational field of a black hole and leave its surface. That is why this surface is called the absolute event horizon. It represents the boundary of the black hole.

Scientists note that these unusual objects is not easy to understand, while remaining within the law of gravitation of Newton. Near the black hole surface gravity is so strong that the usual Newtonian laws are no longer here to act. They should be replaced by the laws of the General theory of relativity. According to one of the three consequences of Einstein's theory, leaving massive body, the light must have red shift, as it ought to experience red shift, as it loses energy to overcome the gravitational field of the star. The radiation that comes from a dense star, like a white dwarf companion of Sirius a, is only slightly offset in the red region of the spectrum. The denser the star, the more this shift, so from a superdense stars absolutely will not come radiation in the visible region of the spectrum. But if the gravitational action of the star increases in the result of compression, the gravitational forces are so great that no light can leave a star. Thus, for any observer opportunity to see a black hole is completely eliminated ! But then the question naturally arises: if it's invisible, how are we able to see it ? To answer this question, researchers have resorted to skillful tricks. Ruffini and Wheeler thoroughly studied this issue and suggested several ways that may not be seen, but at least discover a black hole. Let's start with the fact that when a black hole is born in the process of gravitational collapse, it must radiate gravitational waves, which could traverse space at the speed of light, and for a short time to distort the geometry of space near the Earth. This distortion was manifested in the form of gravitational waves, operating simultaneously on the same tools that are installed on the earth's surface at significant distances from each other. Gravitational radiation could come from the stars, experiencing gravitational collapse. If in the course of ordinary life, the star rotates, then, shrinking and becoming less and less, it will be faster keeping their moment of momentum. Finally it can reach a stage where the speed at its equator will approach the speed of light, that is, to the maximum possible speed. In this case, the star would have been greatly strained and could dispose of the substance. When such a strain energy could get away from the star in the form of gravitational waves with a frequency of about one thousand vibrations per second (1000 Hz).

J.. Weber has set the trap of gravitational waves in the Argonne national laboratory near Chicago and the University of Maryland. They consisted of a massive aluminum cylinders, which were to fluctuate, when gravitational waves will reach the Ground. Used Weber detectors of gravitational radiation react to high (1660 Hz)and very low (1 cycle per hour) frequency. To detect the last frequency, it is sensitive gravimeter, and the detector is the Earth itself. The natural frequency quadrupole oscillations of the Earth is equal to one cycle per 54 min

All these devices were to occur simultaneously at the time when the gravitational wave reached the Earth. Indeed they worked at the same time. But unfortunately, the traps were included too often, about once a month, that looked very strange. Some scientists believe that although the experiments Weber and received the results are interesting, but they are not reliable. For this reason, many are skeptical about the idea of detection of gravitational waves (experimental detection of gravitational waves, similar experiments Weber, were later tested in several other laboratories and not confirmed results Weber. Currently it is considered that experiments Weber wrong).

Roger Penrose, a Professor of mathematics Birkbeck College, University of London, examined the curious case of collapse and the formation of a black hole. He also admits that the black hole disappears, and then manifests itself in different time in some other universe. In addition, he argues that the birth of a black hole during gravitational collapse is an important indication that the geometry of space-time is something unusual. Research Penrose show that the collapse ends with the formation of a singularity, that is, he must go to zero dimensions and infinite density of the object. The latter condition allows another universe to approach our singularity, and it is possible that the singularity will go into this new universe. It may even appear in any other place of our own Universe.

Some scientists consider the formation of a black hole as a small model of what, according to the predictions of the General theory of relativity, in the end can happen with the Universe. It is generally accepted that we live in an ever-expanding Universe, and one of the most important and pressing issues of science concerns the nature of the Universe, its past and future. No doubt, all modern observations point to the expansion of the Universe. however, today one of the most tricky questions is: is slowed down if the speed of this expansion, and if so, will not be compressed if the universe through tens of billions of years, forming a singularity. Apparently, someday we will be able to figure out which way should the universe, but, perhaps, earlier, studying the information that seeps at birth of black holes, and the physical laws that govern their fate, we can predict the final fate of the Universe.

Almost all his life star keeps the temperature and size is almost constant. The value of the main sequence is that most ordinary stars are normal, that is devoid of any special features. We can expect that these stars are subordinated to certain dependencies, such, for example, mentioned the main sequence. Most stars appear on this slanting line - main sequence, because the star could come on this line only for a few hundred thousand years, and after leaving it, to live another few hundred million years, most of the stars obviously still on the main sequence for billions of years. Birth and death are infinitesimally small moments in the life of a star. Our Sun, which is the normal star, is this sequence within 5-6 billion years and, apparently, will it still the same amount of time as the stars with such weight and therefore the chemical composition of the Sun, live 10-12 billion years. The stars are much smaller masses are on the main sequence about 50 billion years. If the mass of the stars in 30 times the sun, the time of its stay on the main sequence will be only about 1 million years.

Let us return to the consideration of the processes, aboutoutgoing birth of a star: she continues to compress, compression is accompanied by increasing temperature. The temperatures creeping up, and that's a huge ball of gas begins to glow, it can already be seen against the dark night sky as dull reddish disc. A significant proportion of its energy radiation continues to have the infrared spectrum. But this is not a star. As a matter of protostar is sealed, it quickly falls to the center, warming up the core of stars up to more higher temperatures. Finally the temperature reaches 10 million To, and then begin to leak thermonuclear reaction - the energy source of all stars in the Universe. As soon as the thermonuclear processes involved in the action, space body turns into a full-fledged star.

Shrinking, dust and gas to form the protostar; its substance is a typical sample of matter surrounding us part of outer space. Speaking about the sample of the substance of the Universe, we mean that this piece mezhzvezdnoi environment 89% consists of hydrogen and 10%helium; elements such as oxygen, nitrogen, carbon, neon, etc., make it less than 1%, and all metals, taken together, does not exceed 0.25%. Thus, the star consists mostly of those elements that are most often found in the Universe. And richer because everything in the Universe presents hydrogen, then, of course, any thermonuclear reactions should proceed with its participation.

Some places there are corners of space with high content of heavy elements, but this is only local anomalies - the remains of the old stellar explosions, razbrosana and russiawhich in the vicinity of heavy elements. We will not dwell on such abnormal areas with high concentrations of heavy elements, and will focus on stars, consisting mainly of hydrogen.

When the temperature in Central protostar reaches 10 million To begin a complex (but studied in detail) of thermonuclear reactions in which course of hydrogen nuclei (protons) form a helium nucleus; every four proton, together, create the helium atom. First, when are connected to each other two protons, there is a heavy atom of hydrogen or deuterium. Then last faced with the third proton, and the reaction is born lighter isotope of helium containing two protons and one neutron.

In the confusion that reigns in the core of a star, fast-moving light helium atoms sometimes collide, resulting receive an ordinary atom of helium, consisting of two protons and two neutrons. Two extra proton back to the hot mixture to ever again to react generating helium. In this process, about 0.7% of the mass is converted into energy. Described the chain of reactions is one of the most important fusion cycles occurring in the cores of stars at a temperature of about 10 million To. Some astronomers believe that at lower temperatures can occur other reactions involving lithium, beryllium and boron. But they immediately make a reservation, that if such reactions and are, their relative contribution to the generation of energy is negligible.

When the temperature in the interior of a star grows again, the action comes another important reaction in which as a catalyst participates carbon. Beginning with hydrogen and carbon-12, this reaction results in the formation of nitrogen-13, which spontaneously decomposes to carbon-13 - isotope of carbon, more severe than the one from which the reaction nachinaushsih-13 picks another proton, turning into nitrogen-14. The last similar way becomes oxygen-15. This element also unstable, and as a result of spontaneous decay is converted into nitrogen-15. And finally nitrogen-15, attaching to itself fourth proton, breaks down into carbon-12 and helium.

Thus, a by-product of these thermonuclear reactions is carbon-12, which can again begin reactions of this type. The Association of four protons leads to the formation of a single atom of helium, and the difference in the mass of four protons and one atom of helium, representing about 0.7% of the original mass, expressed in the form of energy star. In the Sun every second 564 million tons of hydrogen turns into 560 million tons of helium, and the difference is 4 million tons of matter is converted into energy and is radiated to space. It is important that the mechanism of generation of energy in the star depends on temperature.

It is the core temperature of a star determines the speed of the processes. Astronomers believe that at a temperature of about 13 million To the carbon cycle is relatively insignificant. Therefore, at this temperature prevails proton-proton cycle. Temperature increase to 16 million To probably both cycles give equal contribution to the process of generation of energy. When the core temperature rises above 20 million To the prevailing becomes the carbon cycle.

Once the energy star begins to be supported by nuclear reactions, gravitational compression, which started the whole process is terminated. Now self-sustaining reaction may last over time, the duration of which depends on the initial mass of the star and is about 1 million years to 100 billion years or more. During this period the star reaches the main sequence and starts his long life, flowing almost without changes. Eternity holds star in this stage. Nothing special with it does not, it doesn't attract attention. Now it's just a full member of star colony, lost among many brethren.

However, the processes taking place in the core of a star, carry the germs of its coming destruction. When wood or coal burn in the fireplace, heat, and as a by-product of waste generated smoke and ash. In "the fireplace" stellar core hydrogen is a carbon, and helium ash. If from the fireplace from time to time not remove ashes, she could beat him and the fire goes out.

If the kernel stars substance not stirred, in thermonuclear reactions begin to participate layers adjacent to a helium nucleus, which ensures the star energy. Over time, however, the stocks of hydrogen in these layers are drying up and the kernel grows more and more. Finally reached the state when the kernel is not hydrogen. The usual reaction of hydrogen-to-helium cease ; the star left the main sequence and becomes relatively short (but interesting) period of their life, marked by an unusually violent reactions.

When hydrogen becomes a little and he can no longer participate in the reactions, the energy source is increasing. But, as we already know, the star is a finely balanced mechanism, in which the pressure is promoting a star from the inside, fully balanced by gravitational attraction. Consequently, when the generation of energy is waning, radiation pressure drops sharply, and gravitational forces start to compress star. Again there is a drop of a substance to its centre, much like that began with the birth of a protostar. Energy arising during gravitational compression, much more energy now in nuclear reactions, and the star begins to contract. In the upper layers of the star is heated, it expands again and grows in size as long as the outer layers is quite sparse, it is better to let the light from the star. I believe that the star of the type of the Sun may grow so that will fill the orbit of mercury. After the star begins to expand, it would leave the main sequence and, as we have seen, her days are now numbered. From this moment the life of a star starts to fall apart.

When the star shrinks due to the work of gravity forces allocated huge energy, which inflates the star. It would seem that this should lead to a drop in temperature in the kernel. But it is not. Against expectations, the temperature in the core of the star increases dramatically. In a relatively thin layer around the nucleus is still conventional nuclear burn hydrogen, which leads to an increase in the content of helium in the core. When the kernel is concentrated about half the mass of the star, the last expanded to its maximum size and color from white to yellow, then red, because the surface temperature of the star is reduced. Now the star is entering a new phase. The core temperature is rising up until will not exceed 200 million K. At this temperature begins to fade helium, resulting in carbon. Three helium nuclei fuse to become a carbon nucleus, which turns out to be easier than the original three helium nuclei, so this reaction also comes with the release of energy. Again the pressure of radiation, which played such an important role, when the star was on the main sequence begins to counteract gravity, and the core of the star again withheld from further compression. Star returns to the normal size ; as it happens, its surface temperature increases and it becomes red white.

At this point, for some mysterious reason the star becomes unstable. Astronomers believe that variable stars, i.e. stars, periodically changing its luminosity, arise at this stage of stellar evolution, because the compression process is not smooth, and at some stages occur rhythmic fluctuations stars. At this stage, the star can go through a new phase, during which she suddenly throws in interstellar space for a significant amount of matter ; it is, taking the form of an expanding shell can contain a significant part of the mass of the star. Flash some new are repeated many times, and this means that a single flash unit is not enough that the star has reached stability. But with time it gets stability, oscillations disappear, the star begins its a long way to the star cemetery. Even at this stage, the star is still able to activity. It can become a supernova. The reason that the star is capable of this activity, due to the amount of material left it to this stage.

When we discussed the processes in the depths of the star, we said that the main product of nuclear reactions is helium. As processed more and more of hydrogen, is growing helium nucleus of the star. Hydrogen disappears, therefore, the energy release due to this source shall be cancelled. But at a temperature of about 200 million To offer another Avenue by which produces helium into heavier elements, and in the process, energy is released. Two helium atom connected to form atoms of beryllium, which is usually once again breaks into helium atoms. However, temperature and reaction speed is so high that before decay of beryllium, and is joined by a third helium atom and form a carbon atom.

But the process does not stop, because the helium atoms, bombarding carbon, generate oxygen, bombarding the oxygen, give neon, and bombarding neon, produce magnesium. At this stage, the core temperature is still too low for the formation of heavier elements. The core shrinks again, and this continues until then, until the temperature reaches the value of about a billion degrees and will not start the synthesis of heavier elements. If as a result of further compression of the core temperature rises to 3 billion By, heavy nuclei interact with each other until, until it forms iron. The process stops. If the helium atoms will bombard iron nuclei, instead of education, the heavier items will decay of nuclei of iron.

At this stage life of a star to its core is made of iron, is surrounded by layers of nuclei of lighter elements up to helium, and thin outer layer is formed by hydrogen, which still provides some energy. Finally there comes a time when hydrogen is completely consumed and this source of energy is increasing. Cease to act and other mechanisms of generation of energy ; star deprived of all means for the reproduction of its energy reserves. This means that she must die. Now, having exhausted the reserves of nuclear energy, the star can only be compressed and use of the gravitational energy to support their glow. The star will be compressed and glow brightly. When this energy runs out, the star begins to change color from white to yellow and then to red ; finally she stops and starts to radiate a continuous journey into the vast cosmic space in a small dark lifeless object. But on the way to extinction ordinary star undergoes the stage of the white dwarf.