How are black dwarf, White Dwarf, Red Dwarf and Black Hole formed?

Black dwarf is an evolving product of a white dwarf star similar to the size of the sun. At its surface temperature, black dwarf drops, and it stops emitting light and heating. Because the life cycle from star formation to black dwarf evolution is longer than the age of the universe, there is no black dwarf in the present universe. If there are black dwarf in the present universe, it is extremely difficult to detect them. Because they have stopped emitting radiation, if any, they are very small, and most of them are covered by cosmic microwave background radiation. Therefore, the only detection method is gravity detection, but this method is not effective for stars with small mass. Unlike black dwarf, brown dwarfs are too small in mass to generate nuclear fusion of hydrogen atoms. Black dwarf has enough mass to shine in its main sequence star era. Brown Dwarf Brown Dwarf is a star-like celestial body with a mass of about 5 to 90 times that of Jupiter. Unlike ordinary stars, brown dwarfs can't become main sequence stars because of their lack of mass, and their cores will not fuse with hydrogen atoms to emit light and heat. Brown dwarf, but its interior and surface are in convection state, and different chemicals do not exist in the inner layer. At present, people are still studying whether brown dwarfs have had nuclear fusion in a certain position in the past. It is known that brown dwarfs with a mass greater than 13 Jupiter can fuse deuterium. Brown dwarfs, formerly known as "black dwarf", represent stellar objects floating in the universe or objects with insufficient mass for nuclear reactions. But the word "black dwarf" now refers to some white dwarfs that have stopped emitting light and died. The early star model pointed out that a celestial body must have a mass of more than 80 Jupiter to produce a nuclear reaction if it wants to become a real star. The theory of "brown dwarfs" was first put forward in the early 1960 s, which means that brown dwarfs may be more than real stars, because they can't shine, so it is quite difficult to find them. They emit infrared rays, which can be detected by infrared detectors on the ground, but it took decades from their introduction to their confirmation. White Dwarf White Dwarf is a star with low luminosity, high density and high temperature. Because it is white in color and relatively small in size, it is named white dwarf. White dwarfs belong to stars that have evolved into their later years. In the later stage of evolution, a star throws a lot of matter. After a lot of mass loss, if the mass of the remaining core is less than 1.44 solar masses, then the star may evolve into a white dwarf. Some people think that the predecessor of a white dwarf star may be a planetary nebula (a ring-shaped or disk-shaped substance composed of high-temperature gas and a small amount of dust in the universe, and there is usually a very hot star in its center-the central star). Its nuclear energy has been basically exhausted, and the whole star began to slowly cool and crystallize until it finally "died". Brown Dwarf Brown Dwarf is a gaseous celestial body similar to a star, but its mass is not enough to ignite the core fusion reaction. Its mass is between stars and planets. Brown dwarf is a celestial body, which is between the smallest star and the largest planet. Because of this, brown dwarfs are very dim, and it is very complicated to find them, and it is even more complicated to determine their size. Recently, however, astronomers have successfully discovered two brown dwarfs, which form a binary system. After determining their orbital parameters around the same center of gravity, the weight and size of these two brown dwarfs are calculated. It took astronomers 65,438+02 years to discover these two brown dwarfs. They observed more than 300 nights and made 65,438+0,600 measurements. As a result, they calculated all the necessary parameters of two rather young brown dwarfs (less than 1 10,000 years). They are located in Orion, 0/500 light-years away from the Earth. In the binary system, the larger brown dwarf is 50 times larger than Jupiter, while the smaller brown dwarf is 30 times larger than Jupiter, that is, their diameters are 70% and 50% of the diameter of the sun, respectively. Although they are not short at first glance, their mass is only 5.5% and 3.5% of the mass of the sun respectively. Brown dwarfs are called "failed stars". Because of their lack of mass, they can't become burning stars, but their mass is still much larger than Jupiter, the largest planet in the solar system. Astronomers have found huge planetary storms on these strange planets, comparable to the Great Red Spot Storm on Jupiter. Because brown dwarfs will cool over time, gaseous iron molecules on the planet will condense into liquid iron clouds and rain. With further cooling, huge storms will sweep these clouds, causing bright infrared rays to escape into the universe. According to Herodotus diagram, among many stars in the main sequence stage, the size and temperature of red dwarfs are relatively small and low, and they belong to K or M type in spectral classification. They are abundant in stars. Most red dwarfs are less than one-third the diameter and mass of the red dwarf sun, and their surface temperature is lower than 3,500K K. The light emitted is much weaker than that of the sun, and sometimes it can be less than one-tenth of the luminosity of the sun. Because the nuclear fusion of internal hydrogen is slow, they also have a long life. The internal gravity of a red dwarf is not enough to aggregate helium, so it is impossible for the red dwarf to expand into a red giant and gradually contract until the hydrogen is exhausted. Because a red dwarf can live for tens of billions of years, which is longer than the age of the universe, there are no dying red dwarfs at present. People can infer the approximate age of a cluster from the longevity of red dwarfs. Because the stars in the same cluster are formed at the same time, more stars in an older cluster are out of the main sequence star stage, and the rest of the main sequence stars are of low mass, but people can't find any red dwarf star out of the main sequence star stage, which indirectly proves the existence of the age of the universe. At present, the main sequence star stage of the sun has gone through about 4.57 billion years through the computer simulation of star evolution and the cosmic chronology model. According to research, the rapid collapse of a group of hydrogen molecules 4.59 billion years ago formed the third generation of Taurus T star and the first star group, namely the sun. The newborn star is in a nearly circular orbit about 27,000 light-years from the center of the Milky Way. The sun has reached middle age in its main sequence star stage, during which the nuclear synthesis reaction of the stars inside its core fuses hydrogen into helium. At the core of the sun, more than 4 million tons of matter can be converted into energy every second, producing neutrinos and solar radiation. At this speed, the sun has so far converted about 100 mass of matter into energy. The sun as the main sequence star lasts about 654.38+0 billion years. The mass of the sun is not enough to explode into a supernova After 5 billion to 6 billion years, the hydrogen in the sun will be exhausted, and the core is mainly helium atoms, and the sun will become a red giant. When the hydrogen in its core is exhausted, the core will shrink, the temperature will rise and the outer layer of the sun will expand. When its core temperature rises to100,000,000 k, helium will fuse to produce carbon and enter the asymptotic giant branch. When all the helium in the sun is converted into carbon, the sun will no longer shine and become a black dwarf. The ultimate fate of the earth is still unclear. When the sun becomes a red giant, its radius can exceed 1 astronomical unit, which exceeds the current orbit of the earth and is 260 times the current radius of the sun. But at that time, the sun, as an asymptotic giant branch star, will lose about 30% of its current mass due to stellar wind, so it will extrapolate the planetary orbit. At this point alone, the earth may be spared from being swallowed up by the sun. However, new research shows that the earth will still be swallowed up by the sun due to the influence of tides. Even if the earth can escape the fate of being melted by the sun, the water on the earth will be evaporated and the atmosphere will escape. In fact, even when the sun is still the main sequence star, it will gradually become brighter and the surface temperature will slowly rise. The rising temperature of the sun will lead to the rising temperature of the earth's surface after 900 million years, making it impossible for life as we know it at present. In the next 65.438 billion years, the water on the earth's surface will disappear completely. After the red giant stage, the intense pulse generated by heat will break away from the sun's shell and form a planetary nebula. After losing the shell, only the extremely hot star core will become a white dwarf, which will slowly cool and darken for a long time. This is a typical evolution process of low-mass stars [3].