10th Week: Supernovae and Nucleosynthesis: Difference between revisions
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=Supernovae= | =Supernovae= | ||
At the end stage of their evolution stars with masses <math>0.07 M_{\odot} < M < 8 M_{\odot}</math> run out of fuel in their core and form a so called ''white dwarf'' star. Depending on the masses of the stars, the newly formed white dwarf could be made of helium in the core (<math>M<M_{\odot}</math>) and known as a helium white dwarf. And if the mass of main sequence is in the range of <math>0.5 M_{\odot}<M<8M_{\odot}</math>, then the carbon oxygen white dwarf will be formed. For star masses of <math>8 M_{\odot}<M<10M_{\odot}</math> no white dwarf is formed, since the core fuses neon to iron and the star is no more supported by the electron degeneracy pressure due to high mass of the iron core that exceeds the so called Chandrasekhar limit, a limit that gives the stability of white dwarf star against gravitational collapse. These stars further contract and eventually the gravity is balanced out with the neutron degeneracy pressure and the stars formed are called neutron stars. For more massive main sequence stars the gravitational binding energy becomes sufficient to overcome the neutron degeneracy pressure and star is eventually formed into a black hole. | At the end stage of their evolution stars with masses <math>0.07 M_{\odot} < M < 8 M_{\odot}</math> run out of fuel in their core and form a so called ''white dwarf'' star. Depending on the masses of the stars, the newly formed white dwarf could be made of helium in the core (<math>M<M_{\odot}</math>) and known as a helium white dwarf. And if the mass of main sequence is in the range of <math>0.5 M_{\odot}<M<8M_{\odot}</math>, then the carbon oxygen white dwarf will be formed. For star masses of <math>8 M_{\odot}<M<10M_{\odot}</math> no white dwarf is formed, since the core fuses neon to iron and the star is no more supported by the electron degeneracy pressure due to high mass of the iron core that exceeds the so called Chandrasekhar limit, a limit that gives the stability of white dwarf star against gravitational collapse. These stars further contract and eventually the gravity is balanced out with the neutron degeneracy pressure and the stars formed are called neutron stars. For more massive main sequence stars the gravitational binding energy becomes sufficient to overcome the neutron degeneracy pressure and star is eventually formed into a black hole. | ||
The supernovae explosion occurs at the end of a star's lifetime, when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy. If star is not very massive the explosion is due to white dwarf binary system and if the star is very massive, then its core will collapse and in so doing will release a huge amount of energy. This will cause a blast wave that ejects the star's envelope into interstellar space. | |||
==Supernovae Type 1a== | ==Supernovae Type 1a== | ||
Revision as of 09:34, 16 April 2009
Supernovae
At the end stage of their evolution stars with masses run out of fuel in their core and form a so called white dwarf star. Depending on the masses of the stars, the newly formed white dwarf could be made of helium in the core () and known as a helium white dwarf. And if the mass of main sequence is in the range of , then the carbon oxygen white dwarf will be formed. For star masses of no white dwarf is formed, since the core fuses neon to iron and the star is no more supported by the electron degeneracy pressure due to high mass of the iron core that exceeds the so called Chandrasekhar limit, a limit that gives the stability of white dwarf star against gravitational collapse. These stars further contract and eventually the gravity is balanced out with the neutron degeneracy pressure and the stars formed are called neutron stars. For more massive main sequence stars the gravitational binding energy becomes sufficient to overcome the neutron degeneracy pressure and star is eventually formed into a black hole.
The supernovae explosion occurs at the end of a star's lifetime, when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy. If star is not very massive the explosion is due to white dwarf binary system and if the star is very massive, then its core will collapse and in so doing will release a huge amount of energy. This will cause a blast wave that ejects the star's envelope into interstellar space.