What is a black hole? Detailed answer

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What is a black hole? Detailed answer

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What is a black hole?

Black holes, so named in 1967 by American astrophysicist John Wheeler, are nothing more than the result of the gravitational collapse of stars whose mass is more than 2,5 times that of the Sun. In this case, the internal pressure of the star is not able to stop its gravitational collapse. A star rapidly compressed by gravitational forces shrinks to the size of a Schwarzschild sphere, after which no signals from the surface of the star can go outside.

According to general relativity, an observer at a great distance from a collapsed star will never know what is happening inside the Schwarzschild sphere. He will not even see the moment when the surface of the star crosses the Schwarzschild sphere: due to the relativistic time dilation, the star for the observer will approach the gravitational radius for an infinitely long time and "freeze" at sizes close to the gravitational radius.

The size of a black hole, or rather, the radius of the Schwarzschild sphere, is proportional to its mass. For a black hole with a mass of about 10 solar masses, the radius of the Schwarzschild sphere is approximately 30 kilometers.

Astrophysics does not impose any restrictions on the size of a star, and therefore a black hole can be arbitrarily large. If, for example, it has a mass of about 10 million solar (it arose due to the merger of hundreds of thousands, or even millions of relatively small stars), its radius will be about 300 million kilometers, that is, twice the earth's orbit.

Apparently, it is precisely such black holes that are found in the centers of galaxies. In any case, astronomers today count about 50 galaxies, in the center of which, judging by indirect evidence, there are black holes with a mass of about a billion solar masses. In our Galaxy, too, apparently, there is a black hole - its mass is estimated at about 2,4 million solar.

The theory suggests that, along with such supergiants, black mini-holes with a mass of about 100 million tons (the mass of an asteroid with a diameter of only about 200 meters) and a radius comparable to the size of an atomic nucleus should have arisen. They could appear in the first moments of the existence of the Universe as a manifestation of a very strong inhomogeneity of space-time with a colossal energy density.

Author: Kondrashov A.P.

Random interesting fact from the Great Encyclopedia:

What colors of blood, other than red, are common in the animal kingdom?

The blood of vertebrates is red due to the protein hemoglobin, which, when combined with oxygen, becomes red. The only exception are green-blooded skink lizards, which have green blood due to an abnormally high concentration of the bile pigment biliverdin. It is of the same color in some annelids and polychaete worms, but for a different reason - they use the protein chlorocruorin to bind oxygen. Other blood colors in the animal kingdom are also formed due to other proteins: hemocyanin stains the blood of mollusks blue, hemerythrin - the blood of some marine invertebrates purple, and gemovanadin - the blood of ascidians mustard yellow.

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