In societies that are happy in relation to culture, astronomy is in great esteem.
A member of this group, in the distant 1897, created the Atlas of the starry sky (“sky Guide”), which was then reprinted many times. Describing double stars, he admired their beauty: one blue and the other pink, or one orange and the other green.
Double star was surprised and later researchers. In such systems rotating around a common center of mass one can estimate the mass of each component. A follow up study of their spectra has shown that many double stars are not subject to firmly established law: the more mass, the faster star. From the single stars the greater the mass, the higher the temperature and pressure in its core, the more fusion reactions occur, the quicker change of its physical features characteristic of the next stages of evolution. But double stars, sometimes Vice versa.
The cause was that between closely spaced components is an exchange of substance. Such pairs are called Close binary stars. Both stars formed at the same time, but the mass of them were different, and at first, each evolved independently, but then, when the exchange of matter, their paths of development have become more complicated. Their evolution is affected by the mass ratio of the components, the extent to which each of them had to be, the periods of their orbital and axial rotation, the magnetic fields, the change of the distance between them, etc.
The flow of mass begins when one of the stars in the freeze reaction of transformation of hydrogen into helium, and as a result of the instability of the atmosphere extends, in an effort to separate from the kernel. Expands, and fills the atmosphere surrounding the star is Roche lobe the equipotential surface containing the inner point.
This is the point at which the forces of attraction of both components are equal. Therefore, the gas flow from one Roche lobe to another, surrounding the second star is easy, no energy costs, as the point touch both cavities Rocha.
The star couple is very diverse, here we will give only examples of close binary stars and their complex and turbulent evolution.
New, Each of the stars was initially developed independently. Stars of larger mass have already happened all of a thermonuclear reaction, flew the atmosphere and it turned into a white dwarf, which “shone” just cooling.
The star of smaller mass has reached this stage, when the core hydrogen became helium, and the red cooler atmosphere have not yet burned hydrogen swollen, filled Roche lobe and began to flow onto the white dwarf.
He has a new growing atmosphere, the brightness grew. The surface of a white dwarf the exposed core of a larger star is very hot, and hydrogen is a wonderful fuel. In the layer where the atmosphere in contact with the core, the temperature rose and pressure so that the involved fusion reaction. The atmosphere quickly began to heat up and expand. The luminosity of the star increased by almost a million times!
Lower adjacent to the core layers of the atmosphere, expanding with more speed, customized external. The atmosphere turned to the ring nebula, and then split into separate clumps and dispersed into interstellar space.
Exploded not the whole star, as it occurs in supernovae, and only layer. A white dwarf is left unharmed. Therefore, this process is repeated again and again. The New between the explosions thousands of years. The more New explosions occur, so they are weaker. There is even a class stars, whose explosions are repeated all through the decades.
All these events learn from studying spectra. Before the high gloss of its New range is the same as the spectrum of the atmosphere of the normal star continuous with absorption lines, but has a strong line shifts in the short wavelength side, which indicates rapid expansion of the atmosphere.