Gravitational collapse. Neutron stars. Black holes

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 the stars.

Star evolution is a cycle of changes that the star travels during its existence (millions or billion years). When the hydrogen in it ends and turns into helium, a helium core is formed, and the cosmic object begins to turn into a red giant - a star of late spectral classes, which has a high luminosity. Their mass can be 70 times the mass of the Sun. Very bright supergiants are called hypergigants. In addition to high brightness, they are characterized by a short period of existence.

The essence of the collapse

This phenomenon is considered the final point of 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 in the case when gravitational forces cause huge cosmic bodies with a large mass to contract very quickly.

In stars with a mass of more than three solar masses, there is enough material for long-term thermonuclear reactions. When the substance ends, the thermonuclear reaction stops, and the stars cease to be mechanically stable. This leads to the fact that they begin to shrink to the center with supersonic speed.

Neutron stars

When the stars contract, this leads to internal pressure. If it grows with sufficient force to stop the gravitational contraction, then a neutron star appears.

Such a cosmic body has a simple structure. The star consists of the core that the core covers, and it, in turn, is formed from electrons and atomic nuclei. Its thickness is approximately 1 km and is relatively thin, if compared with other bodies encountered 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. Within them, atomic nuclei interact, forming nuclear matter. It is the pressure on her part that does not allow the neutron star to shrink further. This type of stars has a very high speed of rotation. They are capable of making hundreds of revolutions in one second. The process of birth begins with a supernova explosion that occurs during the gravitational collapse of a star.

Supernovas

The supernova outburst is a phenomenon of a sharp change in the brightness of a star. Then the star begins to slowly and gradually fade. Thus ends the last stage of gravitational collapse. The whole cataclysm is accompanied by the allocation 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 a long time after the outbreak. This caused the difficulties in determining the nature of supernovae.

Cooling of the neutron star

After the end of gravitational compression, which resulted in the formation of a neutron star, its temperature is very high (much higher than the temperature of the Sun). The star cools down due to neutrino cooling.

Within a couple of minutes their temperature can drop 100 times. For the next hundred years - another 10 times. After the luminosity of the star decreases, the process of cooling it slows down considerably.

The Oppenheimer-Volkov limit

On the one hand, this indicator reflects the maximum possible weight of a neutron star, in 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 also the lower threshold of the weight of the black hole that were formed during the 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 of 2.5 to 3 solar masses. At the moment, scientists say that the heaviest neutron star is J0348 + 0432. Its weight is more than two solar masses. The weight of the lightest black hole is 5-10 solar masses. Astrophysicists state that these data are experimental and relate only to the 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 leave it. Even bodies that can move at the speed of light (including the quanta of light itself) can not leave 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 whites, they can not be penetrated.

In addition to the 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, just like our planet. Scientists call them primary.

In our Galaxy there is one black hole, which, according to astrophysicists, was formed because of the gravitational collapse of supermassive objects. Scientists say that such holes form the nuclei of many galaxies.

Astronomers of the United States of America suggest that the size of large black holes can be significantly underestimated. Their assumptions are based on the fact that to reach the stars with the speed with which they move through the M87 galaxy, which is 50 million light-years from our planet, the mass of a black hole in the center of the M87 galaxy should be at least 6.5 billion solar masses. At the moment it is considered that the weight of the largest black hole is 3 billion solar masses, that is, more than half the size.

Synthesis of black holes

There is a theory that these objects can appear as a result of nuclear reactions. Scientists gave them the name of quantum black gifts. Their minimum diameter is 10 ^-18 m, and the smallest mass is 10 ^-5 m In

To synthesize microscopic black holes, the Large Hadron Collider was built. It was supposed that with its help it will be possible not only to synthesize the black hole, but also to simulate the Big Bang, which would allow to recreate the process of formation of many cosmic objects, including the planet Earth. However, the experiment failed, since there was not enough energy to create black holes.