10th Week: Supernovae and Nucleosynthesis

Supernovae

At the end stage of their evolution stars with masses $0.07M_{\odot }<M<8M_{\odot }$ 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 ($M<M_{\odot }$) and known as a helium white dwarf. And if the mass of main sequence is in the range of $0.5M_{\odot }<M<8M_{\odot }$, then the carbon oxygen white dwarf will be formed. For star masses of $8M_{\odot }<M<10M_{\odot }$ 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.