Silicon burning process
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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+ + νe | |
| 56Co | → | 56Fe + e+ + νe |
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 life, 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).
See also
- stellar evolution
- Supernova nucleosynthesis
- endothermic nucleosynthesis: