silicon burning process

In astrophysics, silicon burning is a nuclear fusion reaction which occurs in massive stars. It requires temperatures of 2.7×10⁹ K and densities of 3×10¹⁰ kg/m³.

²⁸Si + ²⁸Si	→	⁵⁶Ni + γ
⁵⁶Ni	→	⁵⁶Co + e⁺ + ν_e
⁵⁶Co	→	⁵⁶Fe + e⁺ + ν_e

The silicon burning process is extremely short-lived: a star on average burns its accumulated silicon in one day. It is also the last step in a star's live, since the final product, iron-56, is one of the most stable isotopes in the Universe. Fusion cannot proceed any further except by endothermic processes (such as neutron capture, see r-process, s-process). The star core cannot produce energy anymore and cools down. Then, gravitational contraction is not compensated anymore with energy production, and the star collapse is unavoidable. This ends with a supernova explosion and the formation of a neutron star (or even a black hole, if it is massive enough). The supernova releases a huge amount of energy that makes possible the formation of nuclei beyond iron through rapid capture of neutrons (the r-process).

Silicon Burning Process

See also