On the origin of "stars" species---John Darwin

Do you know that stars also evolve? It does not means literary "strong star" eat "weak star", or something like that. It means a star's state from begin---born--- of star to end---death--- of star.  State of stars is divided to three:"Birth of star", "Maturity of star" and "Stellar remnants".

Birth of star
Story starts with molecular cloud in the space. A molecular cloud mast have mass and be large: for example 1.2*10^37 kg and 9.5*10^14 km. A dense part of molecular cloud rotates and collapses, and as gas falling gas released gravitational energy as heat and it become like disc. A baby star becomes in the center of disk. The protostar is it. More gases in disk is falling down to protostar, and more the protostar become hotter.
If a protostar's masses less than 0.08 of solarmass, you can't see it in the sky. In this star, nuclear fusion(nuclear fusion of hydrogen and hydrogen) can't begin because it is too low temperature. Stars like this are known "brown dwarfs".Else, protostar can become star that shine in the sky. Anyway, the sun masses "1" solarmass. In the sun, nuclear fusion began about 13.7billion.

Maturity of star
The sequence of hydrogen and hydrogen nuclear fusion is called "main sequence star".
After this sequence, Stars like the sun becomes "Red giant". This stars become bigger and bigger. In these, nuclear fusion---but not hydrogen and hydrogen, they are hydrogen and helium--- is happening. If a star's mass less than 0.5 solarmass, this nuclear fusion doesn't happen. If all of hydrogen was cosumed, the star's core become smaller but a star expansion.
If star's mass is nice to happen nuclear fusion of more massive elements:carbon, neon and so on except for more massive than Ferrum---iron, these are made and these will be part of our world. If there were no such star, there are no planet human can and space is more simple.

Stellar remnants
If a star is more bigger, for example, a star that has over 40 solarmass, this star will be black hall,
or a star has 10~40 solarmass, this will make a neutron star. A neutron star is very massive---370 thousand ton per square meter (37t/m^2).
And a star has 0.8 - 3~4 solarmass will be white dwarf. What is white dwarf? It is dense star, solar mass is pressed in earth volume. A famous white dwarf is "Sirius B". Sirius is most bright star in the sky except for the sun. Sirius B is companion star of Sirius. You can't see this with naked eye. Main star of Sirius is too bright.