Stellar Black hole

Collapse

One can consider a black hole of an unspecified mass, by basing only on the law of the gravitation as stated by Newton. However, more the mass is low, more the matter must be confined to train a black hole, who is in infinitely dense theory. One knows in fact no capable process natural to generate a black hole lower than approximately 1,5 times the mass of the Sun, which is due to the nature of the various forces intervening in gravitational collapse.

The collapse of a massive star on itself is an quasi-inevitable process. It could be theoretically avoided in the case of very massive stars (120 solar masses initially) which have large a Métallicité, implying a stellar fort Vent which makes lose with star too mass so that it can crumble thereafter. At the end of its nuclear life , the star contracts under the effect of the Gravité of its own matter.

If the mass of star is lower than the Limite of Chandrasekhar (1.44 solar masses), the dying star will become a white Naine. While a star with a higher mass, but nevertheless smaller than the Limit of Oppenheimer-Volkoff (3,2 solar masses), it is a neutron star which will be the finished product. Beyond this limit, gravity is not counterbalanced any more by the Pression of degeneration of the electrons (as for the dwarf white one), nor by that of the protons (for neutron star). In this case, collapse is inescapable, and the object is transformed into Singularité.

A stellar black hole is defined by three properties: its Mass, its electric Charge and its Angular momentum (the spin ). It is thought that the existing black holes have one angular momentum, but the observation which would come to confirm it was not made yet. In the absolute, the angular momentum of a stellar black hole is that of the star which generated it.

Binary system with x-rays

The black holes in tight Binary systems are observable indirectly by the transfer of matter which is carried out since their stellar companions. A disc of Accrétion is formed around the black hole. This disc can sometimes cause the appearance of jet S relativists who can sometimes appear to have a supraluminic Speed (it is in fact an effect of projection]. The energy released by the heating of the matter on the accretion disc (which reaches temperatures of several thousands of million degrees), causes a fort X-radiation. One then speaks about binary with x-rays. The study of the orbital movement of the system as well as the determination of its angle the slope, makes it possible to calculate the masses of the two components, and thus of that of the black hole.

The binary systems with x-rays are also called Microquasar S, in allusion to the Quasar S which are them galaxies with a supermassif Black hole in the center. However, even if the scales of time and temperatures are different, it would seem that the physics of the microquasars and the quasars is the same one. From where interest to include/understand well the microquasars, much more accessible on human time scales of investigation, than their galactic parents. Among the most famous examples of microquasars, one finds GRS 1915+105, and GRO J1655-40.

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