Elaborated the theory of the origin and evolution of galaxies yet. However, the basic idea of this process appear more distinct.

The formation of galaxies seen as a natural step in the evolution of the hot Universe. Apparently, more than 15 billion years ago in the primary substance due to gravitational instability began isolating protocolary with a characteristic mass order mol. In protokolunu during various dynamic processes occurred selecting groups of protogalactic. Further evolution of protogalactic was determined their own gravitational field and gravity of protokolunu. The variety of shapes of galaxies is due to a variety of initial conditions of education of protogalactic. For example, if the galaxy has arisen from a rapidly rotating protogalactic, to be her spiral, the signs of a slowly rotating - elliptic.

Compression protogalactic lasts about 3 billion years. During this period of transformation of the gas clouds in the star system. Further evolution of the galaxy is determined by complex processes: the evolution of stars, chemical evolution, the structural-dynamic evolution of stellar systems. Stars are formed by gravitational compression of gas clouds. When in the centre of compressed clouds are achieved density and temperature, sufficient for the efficient flow of thermonuclear reactions, born star. In the depths of massive stars is fusion of chemical elements heavier than helium. These items fall within the primary hydrogen-helium Wednesday when explosions of stars or a relaxing after a substance from the stars (stellar wind). Elements heavier than iron are formed in the Grand supernova explosions. Thus, the stars of the first generation enrich primary gas chemical elements heavier than helium. These stars are the oldest and composed of hydrogen, helium, and a very small admixtures of heavy elements. The stars of the second generation admixture of heavy elements more visible because they are formed from already enriched with heavy elements primary gas.

The process of birth of stars comes with the continued contraction of protogalactic, therefore, the formation of stars is closer to the center of the system, and the closer to the center, the higher should be the stars of heavy elements. This conclusion agrees well with data on the content of chemical elements in stars in the halo of our Galaxy and elliptical galaxies. In a rotating protogalactic stars of the future halo formed at an earlier stage of compression when rotation is not yet influenced the General shape of protogalactic. Relics of this era in our Galaxy are globular cluster. His position as they would outline the initial almost spherical in shape young Galaxy.

The mass of gas that are not included in the formed stars, and also emitted during the evolution of these stars, had some orbital moment and under the influence of gravity of the system was down to the plane of symmetry, forming disk. Here in the most dense fragments gas was born a new generation of stars.

About 5 billion years ago ceased compression protogalactic: at this time, the kinetic energy generated by the stars of the disk is equal to the energy of the collective gravitational interaction. In that epoch, it seems, the conditions for the formation of spiral structures, and the birth of stars is already in spiral branches, in which gas is rather dense. These are the stars of the third generation, their ages now - from 1 to 5 billion years. These include our Sun.

A significant part of the substance in the process of star formation turns into a long-lived low-mass stars. A star with a mass of one sun becomes a white dwarf, and the more massive - into a neutron star. These objects do not participate in the evolution of galaxies. The interstellar gas reserves gradually depleted, the birth of stars becomes less intense. In a few billion years, when the are exhausted all reserves of gas, spiral galaxy will turn into a lens-shaped, consisting of a small red stars. Elliptical galaxies are already on this stage: all the gas in them spent 10-15 billion years ago.