When does stellar nucleosynthesis occur?
1 Answer
Stellar nucleosynthesis occurs when the temperatures and pressures are high enough in a star's core to support fusion reactions.
Explanation:
When the core temperature of a star is higher that 10,000,000K, the proton-proton chain reaction can take place which fuses Hydrogen into Helium.
The process starts by the strong force overcoming the electromagnetic force to fuse two Hydrogen nuclei (protons) into Helium-2.
Helium-2 is highly unstable and most nuclei disintegrate back into two protons. Sometimes the weak force is able to convert one of the protons into a neutron a positron and an electron neutrino to form deuterium. This releases energy.
The positron immediately annihilates with an electron releasing energy.
A proton then fuses with deuterium for form Helium-3 and a gamma ray, also releasing energy.
Finally two Helium-3 nuclei fuse to form Helium-4, Hydrogen and releases more energy.
Hotter stars use the CNO fusion process which fuses Hydrogen into Helium-4 using Carbon as a catalyst.
Even hotter stars are able to fuse Helium into Carbon.
