* Nuclear Fission: This process involves splitting a heavy atomic nucleus (like Uranium) into lighter nuclei. This releases a tremendous amount of energy.
* Nuclear Fusion: This process involves combining two light nuclei (like hydrogen isotopes) to form a heavier nucleus (like helium). This process also releases a tremendous amount of energy.
How hydrogen fuses into helium:
The most common fusion reaction in stars is the proton-proton chain reaction:
1. Two protons collide: Two hydrogen nuclei (protons) collide with enough energy to overcome their electrostatic repulsion.
2. Weak interaction: One proton transforms into a neutron, releasing a positron (anti-electron) and a neutrino.
3. Deuterium formation: The proton and neutron combine to form a deuterium nucleus (one proton, one neutron).
4. Further fusion: Deuterium then fuses with another proton to form helium-3 (two protons, one neutron).
5. Helium-4 formation: Two helium-3 nuclei then fuse to form helium-4 (two protons, two neutrons), releasing two protons in the process.
This chain reaction releases a significant amount of energy, which is what makes stars shine. It's also the source of most of the helium in the universe.
