Which happens on the sun fission or fusion?

Answer 1

The nuclear reaction within the Sun is fusion. Four hydrogen nuclei (four protons) are forced together under the intense pressure present to form a helium nucleus (two protons and two neutrons). The neutrons are formed from protons by the weak interaction. The resulting loss of mass is accompanied with a release in binding energy, which drives the cycle and emits tremendous radiation energy.

Answer 2

The sun undergoes nuclear fusion, where hydrogen atoms combine to form helium and release a tremendous amount of energy in the process. This fusion process powers the sun and is responsible for the continuous release of light and heat.