neutron star is the densest star except black hole. At the end of its evolution, a star may become one of the few destinations after a supernova explosion due to gravity collapse. The star whose mass does not reach the level that can form a black hole collapses at the end of its life to form a star between a white dwarf and a black hole, and its density is quite many times higher than that of any matter on earth.

the vast majority of pulsars are neutron stars, but neutron stars are not necessarily pulsars, only pulsars can be considered if they have pulses. Name of celestial body: neutron star nickname: Neutron star area: about 3 square kilometers Meaning: The escape velocity of the star with the highest density outside the black hole (observed) is between 1, and 15. km/s surface temperature: more than 1 million degrees Celsius internal temperature: more than 6 billion degrees Celsius radius: 1-3 kilometers origin, discovery, predecessor, evolution state, nature, size, density, temperature, pressure, magnetic field, energy radiation, structure, area, characteristics, astronomical information, research value, The origin neutron star is the densest star except the black hole (according to the latest hypothesis, a theoretical star, Quark Star, is added between the neutron star and the black hole). Like the black hole, it is an exciting and important discovery in the 2th century, which has opened up a new field for human beings to explore nature, and has had a far-reaching impact on the development of modern physics, becoming one of the four major discoveries in astronomy in the 196s. The density of neutron stars is 8.14 ~ 1.15g per cubic centimeter, which is equivalent to more than 1 million tons per cubic centimeter. This density, that is, the density of the nucleus, is one hundred trillion times that of water. Compared with the dozens of tons/cubic centimeter of white dwarfs, the latter seems to be nothing to mention. If the earth is compressed like this, the diameter of the earth will be only 22 meters! In fact, the density of neutron stars is so great that the mass of neutron stars with a radius of 1 kilometers is equivalent to that of the sun. Like white dwarfs, neutron stars are stars in the late stage of evolution, and they are also formed in the center of old stars. It's just that stars that can form neutron stars are more massive. According to scientists' calculations, when the mass of an elderly star is about 8-2 or 3 times that of the sun, it may eventually become a neutron star, while a star with a mass less than 8 suns can only become a white dwarf. However, the difference between neutron stars and white dwarfs is not just the quality of the stars that generate them. Their material existence state is completely different. Simply put, although the density of white dwarfs is large, it is still within the maximum density range that normal material structure can reach: electrons or electrons, nuclei or nuclei, and the atomic structure is complete. In the neutron star, the pressure is so great that the electron degeneracy pressure in the white dwarf can no longer bear it: the electron is compressed into the nucleus, and the homones are neutralized into neutrons, which makes the atom only composed of neutrons, and the neutron degeneracy pressure supports the neutron star and prevents it from further compression. And the whole neutron star is formed by such nuclei close together. It can be said that a neutron star is a huge nucleus. The density of a neutron star is the density of the nucleus. The mass of neutron stars is so great that the huge gravity makes the light break free in a parabola. Neutron stars are very similar to white dwarfs in the process of formation. When the outer shell of a star expands outward, its core shrinks by reaction. A series of complex physical changes took place in the nucleus under great pressure and the resulting high temperature, and finally a neutron star core was formed. And the whole star will end up with a spectacular explosion. This is the famous "supernova explosion" in astronomy. Neutron star is one of the few destinations that a star may become after its supernova explosion due to gravitational collapse at the end of its evolution. The elements such as hydrogen, helium and carbon in the core of the star are exhausted in the nuclear fusion reaction, and when they are finally transformed into iron, they cannot obtain energy from nuclear fusion. The peripheral materials without the support of thermal radiation pressure will fall rapidly to the core under the traction of gravity, which may lead to the conversion of kinetic energy of the outer shell into heat energy and the explosion of supernova, or the internal region of the star will be compressed into white dwarfs, neutron stars and even black holes according to the different mass of the star. When a white dwarf is compressed into a neutron star, the star is severely compressed, so that the electrons in its constituent materials are merged into protons and converted into neutrons. The diameter is only about ten kilometers, but the material in the top cubic centimeter can weigh one billion tons, and the rotation speed is extremely fast. Because its magnetic axis and rotation axis are not coincident, various radiations such as radio waves generated by the rotation of the magnetic field may be transmitted to the earth in a way of blinking, so it is also called a pulsar. A typical neutron star has a mass of 1.35 to 2.1 times that of the sun, and a radius of 1 to 2 kilometers (the larger the mass, the larger the radius shrinks), that is, 3, to 7, times the radius of the sun. Therefore, the density of neutron stars is between grams and grams per cubic centimeter, which is about the density of atomic nuclei. A dense star whose mass is less than 1.44 times that of the sun may be a white dwarf, but a neutron star whose mass is greater than the Oppenheimer-Volkoff limit (1.5-3. times that of the sun) will continue to collapse by gravity, which will inevitably produce a black hole. Because the neutron star retains most of the angular momentum of the parent star, but the radius is only a tiny amount of the parent star, the reduction of the moment of inertia leads to a rapid increase in the rotation speed, resulting in a very high rotation rate, with a period ranging from 7th of a second to 3 seconds of a millisecond pulsar. The high density of neutron star also makes it have strong surface gravity, which is twice as strong as that of the earth. Escape velocity is the speed required to move an object from gravity field to infinite distance, and it is an index to measure gravity. The escape speed of a neutron star is about 1, to 15, km/s, which means it can reach half the speed of light. In other words, the maximum speed of an object falling to the surface of a neutron star will reach 15, km/s. More specifically, if a person with an average weight (7kg) meets a neutron star, the energy he hits the surface of the neutron star will be equivalent to the power of 2 million tons of nuclear explosion (four times the power of the world's largest nuclear bomb czar). Of course, this is only a hypothesis. If so, this person will be torn to pieces by the powerful tidal force as he gets closer and closer to the neutron star. Discovery In 1932, shortly after the neutron was discovered by chadwick, the Soviet physicist Landau proposed that a class of stars could all be composed of neutrons, so Landau became the first scholar to put forward the concept of neutron star. In 1934, Budd and Zwicky published an article in Physical Review, arguing that supernova explosions can transform an ordinary star into a neutron star, and pointed out that this process can accelerate particles and produce cosmic rays. In 1939, Oppenheimer and volkov established the first quantitative neutron star model by calculation, but their equation of state was an ideal degenerate neutron gas model. Neutron stars are stars in the late stage of evolution, and they are also formed in the center of old stars. It's just that stars that can form neutron stars are more massive. According to scientists' calculations, when the mass of an elderly star is greater than that of ten suns, it may eventually become a neutron star, while a star with a mass less than eight suns can only become a white dwarf. Although the neutron star was put forward as a hypothesis as early as 193s, it has never been confirmed, and the existence of neutron stars has never been observed. Moreover, because the density of neutron stars predicted by theory exceeded people's imagination, at that time, people were generally skeptical about this hypothesis. It was not until 1967 that the pulsar was first discovered by Jocelyn Bell, a student of British scientist hewish. After calculation, its pulse intensity and frequency can only be achieved by a star with small volume, high density and large mass like a neutron star. In this way, the neutron star really becomes a fact from a hypothesis. This is really a great event in astronomy in this century. Therefore, the discovery of pulsars is called one of the four major astronomical discoveries in the 196s. In 1967, astronomers accidentally received a strange radio wave. This kind of electric wave is emitted every 1-2 seconds, just like a person's pulse. People once regarded it as the call of cosmic people, which caused a sensation. Later, hewish, a British scientist, finally figured out that this strange electric wave originally came from a special star that was unknown before, namely a pulsar. This new discovery won hewish the Nobel Prize in 1974. So far, more than 3 pulsars have been discovered, all of which are in the Milky Way. There is a pulsar in the center of the crab nebula. In 27, astronomers discovered the fastest rotating neutron star with the help of the Gamma-ray Telescope (Integral) of the European Aviation Agency (ESA). This neutron star, numbered XTE J1739-285, can rotate 1122 times per second along its axis. According to the concept of the earth, if you turn around for one day, one second on this neutron star can pass more than three years. This discovery overthrew the original limit of 7 revolutions per second. This neutron star is about 1 kilometers in diameter, but its mass is similar to that of the sun, and its density is staggering, reaching 1 million tons per cubic centimeter. Its great gravity constantly captures a large number of hot gases from nearby stars and constantly induces thermonuclear explosions. On October 27th, 21, the British Daily Telegraph reported that astronomers have discovered the largest neutron star in the universe, with almost twice the mass of the sun. This neutron star named PSR J1614-223 is about the size of a small city. Relatively speaking, it is not a big planet, but its density is surprisingly high. The mass of a little substance on it is as high as 5 million tons! The predecessor of a neutron star is generally a star with a mass of 1-29 times that of the sun. The great pressure produced in the process of explosion and collapse has greatly changed its material structure. In this case, not only the shell of the atom is crushed, but also the nucleus is crushed. Protons and neutrons in the nucleus are squeezed out, and protons and electrons are squeezed together and combined into neutrons. Finally, all the neutrons crowded together to form a neutron star. Obviously, the density of neutron stars, even white dwarfs composed of nuclei, cannot be compared with it. On a neutron star, every cubic centimeter of matter weighs 1 million tons or even reaches 1 billion tons. When a star shrinks into a neutron star, its rotation will accelerate, reaching several to dozens of turns per second. At the same time, the contraction makes the neutron star a very strong "magnet", and this "magnet" emits electric waves in a certain part of it. When it rotates rapidly, it regularly and constantly shoots electric waves at the earth like a searchlight on a lighthouse. When the part that emits radio waves is facing the earth, we receive radio waves; When this part deflects with the rotation of the star, we can't receive the radio waves. Therefore, the radio waves we receive are intermittent. This phenomenon is also called "lighthouse effect". The evolution state neutron star is not the final state of the star, it has to evolve further. Because of its high temperature and rapid energy consumption, it maintains luminosity by slowing down its rotation to consume angular momentum. When its angular momentum is exhausted, the neutron star will become a black dwarf without light. Properties As a neutron star, a neutron star has many very unique properties, which have opened our eyes. Because they can never be achieved in the earth laboratory, so that we can understand some of the essence of stars more deeply. To sum up, these properties are: the radius of a typical neutron star is only about 1 kilometers. Outside the neutron star is a solid iron shell with a thickness of about 1 km and a density of 1.11 ~ 1.14 g/cm3. The interior is almost entirely a fluid composed of neutrons, with a density of 1.14 ~ 1.15g/cm3. The density is very high. Density is generally expressed in grams per cubic centimeter. The density of water is 1 gram per cubic centimeter, iron is 7.9 grams, and mercury is 13.6 grams. If we take a cubic centimeter of matter from the pulsar, it can weigh more than 1 million tons, or even reach 1 billion tons. Assuming that the density of our earth has reached this unprecedented alarming level, its average radius is not 6371 kilometers, but only 22 meters! The temperature is extremely high. It is estimated that the center temperature of the newborn neutron star is about to Kelvin. When we compare the sun, we can have a slightly specific concept: the surface temperature of the sun is less than 6℃, and the deeper it goes, the higher the temperature is, and the central temperature is about 15 million degrees. At the initial stage of neutron star formation, its cooling is through the so-called URCA process. When the internal temperature drops to 1 million K, the Urca process stops, and other neutrino processes continue to dominate the cooling. After 1 years, the cooling is dominated by optical radiation. Since then, the surface temperature has been maintained at about k for about 1 thousand years. The pressure is amazing. The pressure in the center of our earth is about 3 million atmospheres, which is more than 3 million times of what we usually call a standard atmosphere. The central pressure of pulsars is thought to reach 1 atmospheres, which is twice as strong as the geocentric pressure and twice as strong as the center of the sun. A particularly strong magnetic field. On the earth, the magnetic field intensity of the earth's magnetic pole is the largest, but it is only ．7Gs (Gauss is the unit of magnetic field intensity, 1Gs= T). The magnetic field of sunspots is extremely strong, about 1～4Gs. However, the magnetic field intensity in the polar region of most pulsars is as high as 1 billion Gs, or even 2 trillion Gs. Scientists have found that neutron stars erupt from the poles. Pulsars are celestial bodies in our Milky Way galaxy, usually thousands of light years away, and the farthest is about 55, light years. According to some scholars' estimates, the total number of neutron stars in the Milky Way should be at least 2,. By the end of 198s, less than five thousandths of the estimated number had been discovered. The task of observation and research in the future is still very arduous. Neutron star has only been discovered for twenty or thirty years. Nevertheless, it has provided scientists with very rich and rare observation data and made contributions in promoting the study of celestial evolution and the study of the physical process and changing law of matter under extreme conditions. At the same time, it also puts forward a series of questions and difficult mysteries to people in this newly developed field. Energy radiation The energy radiation of neutron stars is 1 million times that of the sun, which is about watts. According to the situation of electricity consumption in the world, if all the energy it radiates in one second is converted into electric energy, it will last for billions of years for our earth. From the surface of neutron star to the center, the density of iron crystal increases rapidly from the usual density to g/. There is a plasma outside the neutron star and a solid shell inside the surface, which is mainly composed of lattice lattice lattice of Fe nucleus and degenerate free electron gas with a density of. The density gradually increases from the outside to the inside, so high that electrons are forced to combine with protons in the nucleus to form a series of neutron-rich nuclei, such as Ni, Ge, Zn, Mo and Kr, and then transition to the core, and free neutrons begin to appear.