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Evolution of stars

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Among set of stars by which the sky is covered, huge clouds of a dust and gases, basically hydrogen are scattered. In such interstellar clouds, or fogs, stars are born.

Life expectancy of stars is so great (to tens billions years) that astronomers cannot track a life at least one of them from beginning to end. But they can observe of the stars which are at different stages of development. Having united the obtained data, scientific have tracked the basic stages of a life of typical stars.

a star Birth

a star Birth star Occurrence begins with consolidation of substance in a fog. The formed consolidation gradually decreases in sizes, being compressed under the influence of gravitation. During this compression, or a collapse, the energy warming up gas and a dust and causing their luminescence is allocated. There is a so-called protostar. In its center, or a kernel, density and substance temperature maximum. Having reached temperatures nearby 10 000 000°С, in gas thermonuclear reactions start to proceed. Kernels of atoms of hydrogen incorporate, turning to kernels of atoms of helium. At such synthesis the energy large quantity is allocated. In process konvektsii this energy is transferred to a blanket, and then radiated in space in the form of light and heat. Thus, the protostar turns to the present star.

The Radiation which is starting with a kernel, warms up the gas environment, creating the pressure directed outside, and, thus, interfering with a gravitational collapse of a star. As a result, it finds balance, that is has the constant sizes, constant superficial temperature and constant quantity of allocated energy. A star at this stage of development astronomers name a star of the main sequence, specifying, thus, in a place taken by it on the diagramme of Gertsshprunga-Ressella. This diagramme expresses communication between luminosity and star temperature. Protostars with small weight are never warmed up to the temperatures necessary to start thermonuclear reactions. As a result of compression these stars turn in dim red and even more dim brown dwarfs. The first brown star-dwarf has been opened only in 1987


Giants and dwarfs

Giants and dwarfs Diameter of the Sun is equal approximately 1 400 000 km, surface temperature - nearby 6000°С. The sun radiates yellowish light. Throughout 5 billion years it enters into the main sequence of stars.

Approximately for 10 billion years hydrogen "=юяыштю" on such star it is settled, and in its kernel there is mainly a helium. When "уюЁх=і" there is nothing more, intensity of the radiation directed from a kernel is already insufficient for an equilibration of a gravitational collapse of a kernel. But it is enough to energy allocated thus to warm up surrounding substance. In this cover synthesis of kernels of hydrogen begins, is allocated more energy. The star is shone more brightly, but already by reddish light. Simultaneously it extends, increasing in tens times. Now it is called as the red giant.

The Kernel of the red giant is compressed, and its temperature increases to 100 000 000°С and more. Here there are reactions of synthesis of kernels of helium, transforming it into carbon. Thanks to energy allocated thus the star is shone still any 100 million years. When helium comes to an end, and reactions fade, all star under the influence of gravitation is gradually compressed almost till the sizes of the Earth. Energy allocated thus has enough, that the star (already the white dwarf) continued to be shone brightly some time. Degree of compression of substance in the white dwarf is very high and, hence, its density very big - weight of one table spoon can reach thousand tons.

Life cycle of a star with the weight five times exceeding weight of the Sun, much more shortly, also evolves it a little differently. Such star is much brighter, temperature of its surface 25 000°С and more, the period of stay in the main sequence of stars only about 100 million years. At a stage of the red giant the temperature in a kernel exceeds 600 000 000°С. In it there are reactions of synthesis of kernels of carbon which turns to heavier elements, including iron. Under the influence of allocated energy the star extends till the sizes, in hundreds times exceeding initial. At its this stage name already a supergiant.

Process of manufacture of energy in a kernel suddenly stops, and it is compressed within few seconds. The energy large quantity, forming a catastrophic shock wave is thus allocated. It passes through all star and force of explosion throws out its considerable part in a space, causing the phenomenon known as flash of a supernew star. Similar flash was observed in February, 1987 in the next galaxy - Big by Magellanovom a cloud. During short time this supernew star was shone more brightly the whole billion sun.

The supergiant Kernel is compressed, forming a heavenly body in diameter only 10-20 km and so dense that the teaspoon of its substance can weigh 100 million tons! This heavenly body consists of neutrons and is called as a neutron star. Again formed neutron star differs very strong magnetism and a rotation great speed. The powerful electromagnetic field which is letting out radio-waves and other kinds of radiation is as a result created. They extend from magnetic poles of a star in the form of beams. When they are carried by by our radio telescopes, we perceive them as short flashes, or impulses (English pulse). Therefore we name such stars pulsars.

The First light pulsar has been found out in Krabovidnoj fogs. Its impulses repeat with periodicity of 30 times in a second. Impulses of other pulsars repeat much more often: the FEAST (a pulsing source of a radio emission) 1937 + 21 flashes 642 times a second. Stars with the greatest weight, in tens times exceeding weight of the Sun, too flash, as supernew. But thanks to huge weight their collapse has much more catastrophic character. Destructive compression does not stop even at a stage of formation of a neutron star, creating area in which usual substance stops the existence. There is only one gravitation - so strong that anything, even light, cannot avoid its influence. This area is called as a black hole.