Friday, May 29, 2009

Death of a star.

A star is a nuclear plant: its hydrogen is burned on its core, and turns into helium, by great temperature and pressure. When the hydrogen ends, the star begins to fall over itself, because there's no more hydrogen to burn. So, depending of its mass, it could turn into a supernova, a nova, a neutrons star, a black hole, a pulsar. The most important fact is to know that there's an amount of fuel available, and when it ends, the star begins its final life phase.

There are two nuclear processes in physics, fission (which is generally used in atomic reactors and atomic bombs), and fusion which is used in stars and hydrogen bombs (which are fueled by fission bombs). Both processes drive the production of matter towards iron -- which is approximately in the middle of the periodic table. Fusion works towards creating heaver elements, fission breaks heavier elements down into lighter ones. Iron is the "lowest common denominator". Stars fuse hydrogen until it is converted into helium, then they burn helium into heavier elements (oxygen, carbon, etc.). The reach a breaking point when they cannot fuse these heavier elements into an element with a greater mass than iron. (This involves a relatively complex understanding of the physics of energy production in the procesesses of nuclear fission and fusiion -- both can produce energy according to E=mc^2 but you have to do the a fair amount of math to understand the yields and what is driving the reactions forward). At that point the gravitational mass of the star will cause it to collapse (because the push of the outward energy generation can no longer support the contraction forces of the mass of gravity of the star), which depending upon the mass of the star can result in a nova, a super-nova, a neutron star, or even a black hole

What I know about life cycle of a small star is this:

2nd-a protostar
3rd-It turns to a main sequence star
4th-Red giant(Increase in size)
5th-outer layers of the stars are released
6th-A white dwarf forms
7th-White dwarf further cools
8th-A black dwarf forms

I am not sure whether it is acceptable or wrong, but please tell me what mistake I have made.
Please explain me something about black dwarf.

Thanks to all once again!

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