The fixed star theory of evolution
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The fixed star theory of evolution (こうせいしんかろん, English: stellar evolution) is a theory to handle a change of the structure in the fixed star caused by the birth of the fixed star by last moments in astrophysics.
I liken a fixed star to a creature and, in the fixed star theory of evolution, do death from the birth with the life of the fixed star and use a star of the infanthood, the star in a prime of life, a senile star, a term such as the death of the star. Evolution used in the fixed star theory of evolution is the speech that I likened to a creature, but, unlike the evolution of the creature, expresses a change during the life of the fixed star not the change beyond the generation.
Because the fixed star has own gravity, I am going to always shrink. However, potential energy by the gravity turns into heat when I shrink. In addition, a fusion reaction happens if it becomes the elevated temperature and pressure enough, and a temperature occurs. If temperature of the gas rises by these heat, the gas is going to expand. The fixed star is stable in the place where contraction and expansion was balanced in this way. The fixed star greets last moments when I exhaust gravity and energy by the nuclear fusion without keeping the shrinkage.
I show below the life of the fixed star by the current fixed star theory of evolution.
Table of contents
Birth of the protostar
I receive the shock waves of the supernova explosion that a part of the dark nebula happened near and am compressed, and there is a high part of the density. Then gravity becomes strong, and this part comes to draw the material of neighboring nebulas. Then gravity becomes stronger, and density rises at an increasing tempo. In doing so, because potential energy by the gravity turns into heat, temperature rises, and heat radiation begins. This is a protostar.
Main sequence star
The protostar gradually shrinks and changes the potential energy by the gravity to the heat and raises central temperature. The star of this state is observed as a Taurus Model T star doing arrhythmic strange light. The fusion reaction that hydrogen is converted into helium when central temperature is beyond 10 million K begins to happen. The shrinkage is stopped by big energy to occur by a fusion reaction, and the star becomes the main sequence star.
If a fusion reaction becomes intense in the main sequence star, the whole star expands and lowers temperature and weakens a fusion reaction and if a fusion reaction becomes weak, the whole star shrinks and gives temperature and strengthens a fusion reaction. A fusion reaction is regulated automatically in this way and is stable with constant temperature, structure. I follow until leading hydrogen dries up as for this state, and a pit of helium grows.
Red giant-star
Nuclear fusion of hydrogen goes at the nuclear surface of helium, and the nuclear mass of helium increases. When mass increases, the nucleus of helium rather shrinks, and temperature rises. Because the temperature of the center rises as for hydrogen of the outer stratum part, I expand. The surface temperature of the star decreases with the expansion and becomes the red giant-star. The evolution of this fixed star in the back varies according to the mass.
Wolf Reye star
In the vast mass star where mass exceeds 40 times of the sun, I blow off an outer stratum in the middle of the evolution to a red giant-star, and the part of the internal high temperature is exposed. Therefore it does not become the red giant-star and evolves to a blue big star. Such a fixed star is called a wolf Reye star. The inside of the fixed star evolves like a fixed star with less than 40 times of the sun of mass.
White dwarf
Because sincere distance out of one of a fixed star is poor at gravity in the outer stratum of the red giant-star distantly, gas gradually begins to flow in the neighborhood, and the fixed star loses an outer stratum.
Because mass is the fixed star of less than 50% of sun, and nuclear fusion of helium happens, and the temperature of the central nucleus does not rise, I finish the, by the way, life when I just use up hydrogen, and a fusion reaction stopped. The nucleus of helium which lost an outer stratum becomes the size of the earth degree by the shrinkage. This is a white dwarf. The white dwarf takes long time by heat radiation and cools off slowly.
In addition, mass is equal in the star of less than 50% of sun more than 100 billion years for the life. Because this is longer than age (approximately 13,700 million years) of the current space, so far the star who finished life in this way does not exist.
Cepheid
At the fixed star which mass has a bigger than solar 50%, the nuclear shrinkage of helium goes, and temperature is at a point in time beyond 100 million K, and leading, fusion reactions from helium to carbon and oxygen begin. Then the whole star shrinks and comes back to the state that a main sequence star is near because a fusion reaction regulated in the same way as time of the main sequence star by stability takes place. At this time, the outer stratum of the fixed star is in an unstable condition, and the whole star becomes pulsating Cepheid.
Mira type variable star
When leading helium dries up, in the same way as time when hydrogen dried up, a nucleus of carbon in the center and oxygen begins to shrink, and a fusion reaction of helium begins to happen at the outskirts. And the expansion begins again, and the fixed star becomes the red giant-star. The outer stratum of the fixed star is in an unstable condition when I advance than degree with the expansion, and it is the Mira type variable star where the whole star pulsates. The Mira type variable star releases the gas of the outer stratum with pulsation in the neighboring space.
Because carbon causes nuclear fusion, and the temperature of the central nucleus does not rise at the fixed star with less than 8 times of the sun of mass, it is in the white dwarf which is a nucleus of carbon and oxygen which lost an outer stratum in the same way as the case of the fixed star of less than 50% of the sun, and mass finishes the life. The gas released by people shines as a planetary nebula.
Supernova
At the fixed star with more than 8 times of the sun of mass, the temperature of the central nucleus is beyond 600 million K and a fusion reaction of carbon happens and generates neon and magnesium.
Mass is a fixed star of 8-10 times of the sun, and neon and magnesium begin to cause an electronic capture reaction when temperature rises more. Then the pressure with the central nucleus falls at a stretch, and gravity is not supported, and the fixed star shrinks at a stretch. This is gravitational collapse.
At the fixed star with more than 10 times of the sun of mass, a fusion reaction moves more. When silicon is beyond 2,500 million K by nuclear fusion of oxygen more when the temperature of the central nucleus is beyond 1,500 million K, iron is produced by nuclear fusion such as silicon. Because atomic number is the atomic nucleus that the atomic nucleus of the iron neighborhood is the most stable, the nuclear fusion no longer advances. Furthermore, the reaction that an atomic nucleus of iron is broken down into helium when the temperature of the central nucleus of iron rises and surpasses 10 billion K begins. Because this resolution is endothermal reaction, after all the pressure with the central nucleus falls at a stretch in the same way and has gravitational collapse.
In the case of the gravitational collapse, potential energy by the gravity of the vast quantity is released, and the whole fixed star vanishes. This is a supernova explosion.
Neutron star
A central nucleus of around 10km in diameter that mass was crushed by gravitational collapse in the case of a fixed star to around 10-20 times of the sun is left. It is the neutron star which an electron is absorbed in an atomic nucleus for very strong gravity as for this, and the most of the star become from a neutron. A diameter is around 10km, but the mass is a very high-density star of the degree same as the sun.
Black hole
Gravitational collapse progresses without supporting the gravity in the case of the fixed star which mass has a bigger than 30 times of the sun even if it becomes the neutron star, and it is in the black hole which shrank to the maximum.
Comparison
| The sun | White dwarf | Neutron star | Black hole | |
|---|---|---|---|---|
| Size | 1,390,000㎞ | 10,000㎞ | 10km | 3km |
| Density (1cm3) | 1 g | 500㎏ | 500 million㎏ | 20 billion㎏ |
| Gravity at the surface | 28G | 100,000 G | 100 billion G | 2 trillion G |
| Weight (60 kg) at the surface | 2t | 8,000t | 8,000,000,000t | 90,000,000,000t |
Allied item
This article is taken from the Japanese Wikipedia The fixed star theory of evolution
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