In space, many amazing things happen, as a result of which new stars appear, old ones disappear and black holes form. One of the magnificent and mysterious phenomena is the gravitational collapse, which ends the evolution of stars.
Stellar evolution is a cycle of changes that a star has traveled over a period of its existence (millions or billion years). When the hydrogen in it ends and turns into helium, a helium core is formed, and the space object itself begins to turn into a red giant - a star of the late spectral classes, which has high luminosity. Their mass can be 70 times the mass of the sun. Very bright supergiants are called hypergiants. In addition to high brightness, they have a short period of existence.
Essence of collapse
This phenomenon is considered the endpoint of the evolution of stars whose weight is more than three solar masses (the weight of the Sun). This value is used in astronomy and physics to determine the weight of other cosmic bodies. Collapse happens when gravitational forces cause huge cosmic bodies with a large mass to compress very quickly.
In stars weighing more than three solar masses, there is enough material for continuous thermonuclear reactions. When the substance ends, the thermonuclear reaction ceases, and the stars cease to be mechanically stable. This leads to the fact that they begin to compress toward the center with supersonic speed.
Neutron stars
When the stars are compressed, this leads to internal pressure. If it grows with sufficient strength to stop gravitational contraction, a neutron star appears.
Such a cosmic body has a simple structure. A star consists of a core, which is covered by the core, and it, in turn, is formed from electrons and atomic nuclei. Its thickness is approximately 1 km and is relatively thin when compared with other bodies found in space.
The weight of neutron stars is equal to the weight of the Sun. The difference between them is that they have a small radius - no more than 20 km. Inside them, atomic nuclei interact with each other, thus forming nuclear matter. It is the pressure from her side that prevents the neutron star from contracting further. This type of star has a very high rotation speed. They are able to make hundreds of revolutions in one second. The birth process begins from a supernova explosion that occurs during the star’s gravitational collapse.
Supernovae
A supernova flash is a phenomenon of a sharp change in the brightness of a star. Further, the star begins to slowly and gradually fade away. So ends the last stage of gravitational collapse. The whole cataclysm is accompanied by the release of a large amount of energy.
It should be noted that the inhabitants of the Earth can see this phenomenon only after the fact. Light reaches our planet long after the outbreak. This has caused difficulties in determining the nature of supernovae.
Neutron star cooling
After the end of gravitational compression, as a result of which a neutron star was formed, its temperature is very high (much higher than the temperature of the Sun). The star cools down thanks to neutrino cooling.
Within a couple of minutes, their temperature may drop 100 times. Over the next hundred years - another 10 times. After the luminosity of a star decreases, the process of its cooling slows down significantly.
Oppenheimer-Volkov limit
On the one hand, this indicator reflects the maximum possible weight of a neutron star, at which gravity is compensated by a neutron gas. This does not allow the gravitational collapse to end with the appearance of a black hole. On the other hand, the so-called Oppenheimer-Volkov limit is at the same time the lower threshold of the black hole weight, which were formed during stellar evolution.
Due to a number of inaccuracies, it is difficult to determine the exact value of this parameter. However, it is assumed that it is in the range from 2.5 to 3 solar masses. At the moment, scientists claim that the heaviest neutron star is J0348 + 0432. Its weight is more than two masses of the sun. The weight of the lightest black hole is 5-10 solar masses. Astrophysicists claim that these data are experimental and concern only currently known neutron stars and black holes and suggest the possibility of the existence of more massive ones.
Black holes
A black hole is one of the most amazing phenomena that occur in space. It is a region of space-time where gravitational attraction does not allow any objects to get out of it. Even bodies that can move at the speed of light (including quanta of light itself) are not capable of leaving it. Until 1967, black holes were called “frozen stars,” “collapsars,” and “collapsed stars.”
The black hole has the opposite. It is called a white hole. As you know, it is impossible to get out of a black hole. As for the whites, they cannot be penetrated.
In addition to gravitational collapse, the cause of the formation of a black hole can be a collapse in the center of the galaxy or protogalactic eye. There is also a theory that black holes appeared as a result of the Big Bang, like our planet. Scientists call them primary.
There is one black hole in our Galaxy, which, according to astrophysicists, was formed due to the gravitational collapse of supermassive objects. Scientists claim that such holes form the nuclei of many galaxies.
Astronomers from the United States suggest that the size of large black holes can be significantly underestimated. Their assumptions are based on the fact that for the stars to reach the speed with which they move along the M87 galaxy, located 50 million light-years from our planet, the mass of the black hole in the center of the M87 galaxy should be at least 6.5 billion solar masses. At the moment, it is generally accepted that the weight of the largest black hole is 3 billion solar masses, that is, more than two times less.
Black hole synthesis
There is a theory that these objects can appear as a result of nuclear reactions. Scientists gave them the name quantum black gifts. Their minimum diameter is 10 -18 m, and the smallest mass is 10 -5 g.
For the synthesis of microscopic black holes, the Large Hadron Collider was built. It was assumed that with its help it will be possible not only to synthesize a black hole, but also to simulate the Big Bang, which would recreate the process of formation of many space objects, including planet Earth. However, the experiment failed because there was not enough energy to create black holes.