The nuclear reactions that occur in the core of the Sun are responsible for its energy production, and they primarily involve the fusion of hydrogen nuclei (protons) into helium nuclei. The primary nuclear reaction in the Sun is called the "proton-proton chain" or "pp-chain," which consists of several steps:
Proton-Proton Chain Step 1: Two protons (hydrogen nuclei) come together and fuse to form a deuterium nucleus (one proton and one neutron) through the weak nuclear force. This step is relatively slow because it relies on the weak interaction.
H + H -> D + e+ + νe
Where:
H represents a hydrogen nucleus (proton).
D represents a deuterium nucleus.
e+ represents a positron.
νe represents an electron neutrino.
Proton-Proton Chain Step 2: The deuterium nucleus produced in the first step combines with another proton to form a helium-3 nucleus.
D + H -> He-3 + γ
Where:
He-3 represents a helium-3 nucleus.
γ represents a gamma-ray photon.
Proton-Proton Chain Step 3: Two helium-3 nuclei collide and fuse to create a helium-4 nucleus (two protons and two neutrons) and two protons. This is the final step in the process, and it releases a significant amount of energy in the form of gamma-ray photons.
He-3 + He-3 -> He-4 + 2H
Where:
He-4 represents a helium-4 nucleus.
2H represents two protons.
These nuclear reactions release a tremendous amount of energy in the form of gamma-ray photons, which then undergo multiple scattering and absorption processes, eventually emerging from the core of the Sun as visible light and other forms of electromagnetic radiation. This continuous fusion of hydrogen into helium in the Sun's core provides the energy that powers the Sun and makes it shine. This energy sustains life on Earth by providing heat and light.