black hole
100000 why - what is a black hole
Mechanical knowledge tells us that gravitation is everywhere. It is directly proportional to the mass of an object and inversely proportional to the square of distance. Then, of course, there is gravitation between the various parts of any star. However, the reason why a star can maintain a large sphere without being "collapsed" by gravity is that there are other forces to compete with gravity. This force is the expansion force generated by the gas heated by the thermonuclear reaction in the star.
Black holes have strong gravitation
The basic process of thermonuclear reaction is to combine lighter hydrogen atoms into heavier helium atoms, which will release a lot of heat. When the nuclear fuel gradually runs out, the stars begin to age and are on the verge of death. At this time, the gas will gradually cool down, and the gas pressure against gravity will be greatly reduced. As a result, the outer part of the star collapses rapidly to the center under the strong gravitational force, and the volume of the star shrinks rapidly. In the process of collapse, a rebound shock wave will be formed inside the star, and the gas in the outer layer of the star will explode under the action of the rebound shock wave, throwing part of the gas into space. Depending on the situation, supernova explosion or gamma ray burst will occur.
Black holes that devour stars
The fate of the next step depends on the mass of the original star. If the original star has a small mass and the collapsed core is less than 1.4 solar masses, when the star shrinks to a certain extent, a force called "electron degeneracy pressure" (see note) can compete with gravity, and the star stops collapsing. The star formed at this time is called "white dwarf". There is still a small amount of combustible material on the surface of this star, but the temperature is very high, so the color is "white". In addition, this shape is very small, that is, "very short", so it is called a white dwarf.
Stars evolve into white dwarfs
If the mass of the star before the explosion is relatively large, and the collapsed core is greater than 1.4 solar masses but less than 3.2 solar masses, the gravity will be stronger. At this time, the electronic degeneracy pressure cannot compete with the gravity, and the star will collapse further. At this time, another force - "neutron degenerate pressure" appears and plays a role, which can balance with gravity. The star then stopped collapsing. The stars formed at this time are called "neutron stars". The mass gap between neutrons and stars is very small, but the mass of neutrons is only 2 times of that between neutrons and stars, so it is very small!
Neutron stars formed by stellar evolution
If the collapse core of an explosive star is higher than 3.2 solar masses, the gravity will be very strong, and even the neutron degeneracy pressure cannot be balanced with it, so the star can only collapse further and become a black hole!
black hole
Effect drawing of supernova explosion
Gamma ray burst
Due to the practical difficulty of black hole observation, those who claim that a star is a black hole usually give only a few fuzzy photos or some data, and all the characteristics of the black hole cannot be fully verified. The general media reports actually have only some information, which can not meet the data requirements of professional celestial physics. Therefore, there is no black hole in the astronomical database, only black hole candidate stars.
Mysterious black hole