Bright Sword starts with the grenade flat.

Chapter 485 Electron Degenerate Star
In fact, if it weren't for the electron degenerate state, there would be no white dwarfs, and all the stars in the universe would become neutron stars or quark stars, or black holes, so white dwarfs are also called electron degenerate stars.

You should know that in the main sequence stage of medium and low mass stars, after the hydrogen fusion reaction ends, helium fusion will occur in the core, that is, every three helium nuclei will fuse into a carbon nucleus, and the carbon nucleus will then capture other helium nuclei to form an oxygen nucleus, and expand into a red giant.

Of course, unlike hydrogen fusion, the reaction of helium fusion is very fast, so it will form a helium flash, which is the case with the sun. In fact, if helium fusion was not too fast, if it was as slow as hydrogen fusion, then the blue planet where Liu Xiu was would not have to be equipped with a planetary engine to run away.

This is like igniting TNT with a match, which is fuel for heating and cooking, but if it is ignited with a detonator, it becomes a deadly explosive.

Although hydrogen fusion and helium fusion both produce energy through fusion, their fusion speeds are completely different.

Then, when the radiation pressure of the red giant star cannot balance the gravity, the exterior expands outward and continues to cool, while the internal helium core shrinks and collapses under the influence of gravity. The compressed matter continues to heat up, and eventually the core temperature will exceed 100 million degrees, so the helium begins to fuse into carbon.

After millions of years, the helium core burns out and the structure of the star is no longer so simple: the outer shell is still a mixture mainly composed of hydrogen, and there is a helium layer underneath it, and there is a carbon ball buried inside the helium layer.

The nuclear reaction process becomes more complicated, and the temperature near the center continues to rise, eventually converting carbon into other elements. At the same time, unstable pulsation oscillations begin to occur outside the red giant: the star radius sometimes increases, sometimes decreases, and the stable main sequence star becomes an extremely unstable giant fireball. The nuclear reaction inside the fireball also becomes increasingly unstable, sometimes strong, sometimes weak.

At this time, the density of the core of the star has actually increased to about ten tons per cubic centimeter. At this time, a white dwarf has been born inside the red giant.

When the instability of a star reaches its limit, the red giant will explode, throwing all the matter outside the core away from the star body, and the matter will spread outward to form a nebula. The remaining core is the white dwarf we can see. Therefore, white dwarfs are usually composed of carbon and oxygen. But it is also possible that the temperature of the core can reach the temperature that burns carbon but is still not enough to burn neon. At this time, a white dwarf with a core composed of oxygen, neon and magnesium can be formed. Occasionally, there are some white dwarfs composed of helium, but this is caused by the mass loss of the binary star.

There is no more matter in the interior of a white dwarf for nuclear fusion reactions, so the star no longer produces energy. At this time, it is no longer supported by the heat of nuclear fusion to resist gravitational collapse, but by the electron degeneracy pressure generated by extremely high-density matter. In physics, for a non-rotating white dwarf, the maximum mass that can be supported by electron degeneracy pressure is 1.4 times the mass of the sun, which is the Chandrasekhar limit.

Many carbon-oxygen white dwarfs approach this mass limit, and sometimes, through mass transfer from a companion star, the white dwarf may explode as a supernova via a carbon detonation process.

The temperature of a white dwarf is very high when it is formed, but because it has no energy source, it will gradually release its heat and gradually cool down, which means that its radiation will gradually decrease from the initial high color temperature over time and turn red. After a long time, the temperature of the white dwarf will cool to a brightness that can no longer be seen, and it will become a cold black dwarf.

The electron degeneracy pressure that maintains the existence of white dwarfs is generated by the Pauli exclusion principle. In stellar physics, it causes the existence of white dwarfs.

However, electron degeneracy pressure is not the force we understand. It is an exchange interaction, which is completely different from the interaction of the four fundamental forces. It does not require the exchange of medium particles. The exchange interaction only occurs between identical particles. It is essentially an interference effect of wave functions and does not involve any "force".

It is similar to molecular thermal motion. When the temperature rises, the molecular thermal motion intensifies and the volume of the object increases. At this time, we cannot think that a certain force causes the volume of the object to increase. So we can imagine the electron degeneracy pressure as the electron gas pressure generated by "electron thermal motion".

In fact, electron degeneracy pressure is ubiquitous, but under normal circumstances, this pressure is so small that it can be ignored. But when the electron density is high enough and the temperature is low enough, it will dominate. For example, in a white dwarf, the electromagnetic force between atoms cannot withstand the violent compression of gravity, and the electron shell of the atom is crushed, forming a state where free electrons travel in the lattice, or the atomic nucleus floats in the electron ocean.

At this point, we can imagine the situation as all the atomic nuclei and electrons together forming a super large molecule. According to the Pauli exclusion principle, an atomic orbital in a molecular orbital can only accommodate two electrons with opposite spin directions.

Since the lower the orbital energy level, the closer the electron is to the nucleus. When matter is compressed to a very high density, gravity will try to shorten the distance between the electron and the nucleus, and the low-energy orbit will be filled with electrons. The Pauli exclusion principle does not allow two electrons to be in the same state. Electrons approaching each other will generate a new repulsive force, preventing the volume from further shrinking.

Of course, the force of electron degeneracy at this time can be equal to the gravity, thus maintaining the shape of the white dwarf, but this is also when the mass of the white dwarf is relatively small. Once the mass of the white dwarf increases and is greater than 1.4 times the mass of the sun, then gravity will overcome the electron degeneracy force.

At this time, gravity will squeeze the electrons into the protons in the nucleus, causing the nucleus to no longer exist, so at this time, the white dwarf becomes a neutron star.

Of course, neutrons also have their own electron degeneracy pressure to keep the neutron star from resisting its own gravity and preventing further collapse.

However, when the mass of the neutron star continues to increase to more than 2.1 times that of the sun, the gravity will naturally continue to increase, and then overwhelm the degeneracy pressure of the neutrons, crushing the neutrons that make up the neutron star. Neutrons are composed of quarks.

Therefore, the quark star is the natural next to the neutron star, and then the degeneracy pressure of the quarks continues to resist the gravity to maintain a weak balance and prevent it from continuing to collapse.

In the existing physics of wandering blue stars, quarks are the smallest basic units of matter. Therefore, after quark stars, the matter with the highest density will naturally be considered to be a black hole.

The guy ranked first has a density that reaches an incomprehensible level. This first place is the black hole that we are all very familiar with.

Black holes are also formed by the collapse of massive stars, but the high density of black holes makes their existence form completely different from the previous two.

Scientists at the current location of the Wandering Blue Star do not know exactly what the inside of a black hole is like, but they generally believe that the interior of a black hole is just a singularity, so the matter sucked into the black hole is gathered in this small point with an incomprehensible density.

But the most crucial thing is whether there are other high-density celestial bodies between black holes and quark stars. After all, we cannot assume that there are no smaller basic units just because humans on the wandering blue planet have discovered that quarks are the smallest basic units of matter.

(End of this chapter)