Black holes of stellar masses are formed as the final stage of the star's life: after complete burning out of thermonuclear fuel and termination of the reaction, the star theoretically should start to cool down, which will lead to a decrease in internal pressure and compression of the star under the influence of gravity. Compression can stop at a certain stage, and can go into a rapid gravitational collapse .
Depending on the mass of the star and the torque, the following final states are possible:
- Extinguished very dense star, consisting mainly, depending on the mass, of helium , carbon , oxygen , neon , magnesium , silicon or iron (the main elements are listed in ascending order of mass of the star's rest). Such remains are called white dwarfs , their mass is limited from above by the Chandrasekhar limit .
- Neutron star whose mass is limited by the Oppenheimer-Volkov limit .
- Black hole
As the mass of the remainder of the star increases, the equilibrium configuration moves down through the sequence described. The rotational moment increases the limiting masses at each step, but not qualitatively, but quantitatively (maximum 2-3 times).
The conditions (mainly mass) under which the black hole is the end state of the evolution of a star are not well studied, since for this it is necessary to know the behavior and states of matter at extremely high densities that are inaccessible to experimental study. Additional complexity is the modeling of stars in the later stages of their evolution due to the complexity of the chemical composition that arises and the sharp decrease in the characteristic time of the processes. It suffices to mention that some of the largest cosmic catastrophes, supernova explosions , arise precisely at these stages of the evolution of stars . Different models give a lower estimate of the mass of the black hole resulting from the gravitational collapse, from 2.5 to 5.6 solar masses. The radius of the black hole is very small - several tens of kilometers.
Subsequently, a black hole can grow due to the absorption of matter - as a rule, it is the gas of a neighboring star in binary stellar systems (a black hole colliding with any other astronomical object is very unlikely due to its small diameter). The process of gas falling on any compact astrophysical object, including a black hole, is called accretion . At the same time, due to the rotation of the gas, an accretion disk is formed in which the substance accelerates to relativistic velocities, heats up and as a result strongly emits, including in the X-ray range , which makes it possible in principle to detect such accretion disks (and, therefore, black holes) using ultraviolet and x-ray telescopes . The main problem is the small size and difficulty of detecting differences in the accretion disks of neutron stars and black holes, which leads to uncertainty in the identification of astronomical objects with black holes. The main difference is that gas falling on all objects sooner or later encounters a hard surface, which leads to intense radiation during deceleration, but a cloud of gas falling on a black hole due to an unlimitedly growing gravitational time dilation (red shift) just fading away quickly when approaching the event horizon, as observed by the Hubble telescope in the case of the source Cygnus X-1 [1] .
The collision of black holes with other stars, as well as the collision of neutron stars, causing the formation of a black hole, leads to a powerful gravitational radiation , which is expected to be detected in the coming years with the help of gravitational telescopes . Currently, there are reports of observations of collisions in the X-ray range [2] . On August 25, 2011, it was reported that for the first time in the history of science, a group of Japanese and American experts was able to fix the moment of death of a star that a black hole absorbs in March 2011 [3] [4] .
On February 11, 2016, the LIGO and Virgo collaborations announced the first direct observation of gravitational waves , the discovery was possible due to the discovery of the heaviest black holes of stellar masses ever observed [5] .
Notes
- ↑ 'Death Spiral' Around the Black Hole Yields Tantalizing Evidence of an Event Horizon (Eng.) (Not available link) (January 11, 2001). The appeal date is January 24, 2010. Archived March 16, 2010.
- ↑ Astronomers have proved: black holes really “eat up” stars
- ↑ Vasily Golovnin. Scientists from Japan and the United States for the first time in history managed to fix the moment of death of a star (Inaccessible link) . ITAR-TASS (08/25/2011). The appeal date is August 25, 2011. Archived July 29, 2013.
- ↑ Astronomers weighed a predatory hole in the constellation of the Dragon (Inaccessible link) . Lenta.ru (08/25/2011). The appeal date is August 25, 2011. Archived on October 3, 2011.
- ↑ Igor Ivanov. Gravitational waves - open! Elements of Big Science (02/11/2016). The appeal date is February 14, 2016.