Molecular clouds, these "factory of stars", produce the stars of various types. The mass range of newborn stars extends from a few hundredths to 100 Solar masses, with little stars formed much more frequently than larger ones. On average in the Galaxy are born annually about a dozen stars with a total mass of about five Solar masses.

About half of the stars are born to single; other form double, triple and more complex systems. The more features, the more rare are such systems. Famous stars, containing up to seven components, more complex, not found yet.

Causes of double and multiple stars are quite clear: the initial rotation of the gas cloud does not allow it to compress into one compact star. The more compressed the cloud, the faster it rotates (known as "the effect of a figure skater", which is a consequence of the law of conservation of angular momentum). Increasing compression centrifugal force at first do the cloud flat as cheesecake, and then pull in the "melon" and torn in half. Each of the halves, to contract further, continues to move in an orbit around a common center of mass. If further compression does not break it into parts, there is a double star, and if the division continues - born more complex multiple of the system.

"The first cry" newborn stars

The emerging and very young stars are often surrounded by a dust shell - residues of a substance that has not yet hit the star. The shell does not issue from the inside starlight and completely recycles it into infrared radiation. Therefore, most young stars are usually manifest themselves only as infrared sources.

At the initial stage of life "behavior" stars very much depends on its mass. Low luminosity of low-mass stars allows them long delays at the stage of slow compression, "eating" gravitational energy only. During this time, the shell has time to partially settle on a star, and also to form a circumstellar dust disk. Evolution as a massive star runs so fast that the star is home to most of my life surrounded by the remains of its protostar shell, often called the cocoon of gas and dust.

An example of the stars of the cocoon is the object beklina - Neugebauer in the Orion nebula. It is in the centre is compact and very dense clusters of protostars. Of them it is the most massive: the star inside the cocoon has a mass about eight solar. Its luminosity is close to 2 thousand Sunny and the temperature of the radiation cocoon around 600 K. Therefore, the object beklina - Neugebauer was opened by two astronomers whose name it bears, in 1966 as a powerful IR source is Now known already more than 250 objects of this type. Their temperature dust cocoons 300-600 To. Some of them the radiation had almost destroyed the cocoons: observations show that the substance is expanding at the rate of 10-15 km/S.

The cloud becomes a star

A star is born lasts millions of years, and is hidden from us in the depths of dark clouds, so the process is virtually inaccessible to direct observation. Astrophysicists are trying to explore it in theory, with the help of computer simulation. Turning a fragment of clouds in the star accompanied by gigantic change in the physical conditions: the temperature of the substance increases by approximately 106 times, and the density - 1020 times. Tremendous changes all the characteristics of the emerging stars are the main difficulty theoretical consideration of its evolution. At the stage of such changes, the original object is not a cloud, but not a star. Therefore, it is called a protostar (from the Greek. "protos" - "first").

In General terms, the evolution of the protostar can be divided into three stages, or phases.

The first stage - separation portion of the cloud and its seal - we have already considered. After him comes the stage of fast compression. At the beginning of the radius of the protostar about a million times more sun. It is completely opaque to visible light, but transparent to infrared radiation with a wavelength greater than 10 microns. Radiation carries away the excess heat produced by compression, so that the temperature does not rise and the pressure of the gas shall not prevent the collapse. There is a fast compression, almost free fall substances to the center of the cloud.

However, as the compression protostar is less transparent, which makes the output radiation and causes a rise in temperature of the gas. At some point protostar is practically transparent for own thermal radiation. The temperature, and with it the gas pressure increase rapidly, the contraction is slowing.

Warmer temperatures cause significant changes of properties of substances. At a temperature of several thousand degrees molecules are split into individual atoms, and at a temperature of about 10 thousand degrees ionised atoms, i.e. destroyed their electron shell. These energy-intensive processes for some time delay the growth of temperature, but then he resumed. Protostar quickly reaches the state where gravity is almost balanced by the internal pressure of the gas. But because the heat is still a little goes outside, and other energy sources, in addition to compression, protostar no, she continues to slowly shrink and the temperature in its depths is increasing.

Finally, the temperature in Central protostar reaches several million degrees, and start the fusion reaction. Heat due to the heat fully offset the cooling protostar from the surface. Compression stops. Protostar becomes a star.