The fusion of hydrogen nuclei in the Sun produces helium, energy, and neutrinos.

Here's a breakdown of the process:

* Hydrogen Fusion: The Sun's core is incredibly hot and dense, allowing hydrogen nuclei (protons) to overcome their electrostatic repulsion and fuse together.

* Deuterium Formation: Two protons fuse to form deuterium, a heavier isotope of hydrogen, releasing a positron (antimatter electron) and a neutrino.

* Helium Formation: Deuterium then fuses with another proton to form helium-3, releasing gamma rays (high-energy photons). Two helium-3 nuclei then fuse to create helium-4, releasing two protons.

Overall reaction: 4 protons → 1 helium-4 nucleus + 2 positrons + 2 neutrinos + energy (in the form of gamma rays and kinetic energy)

This process is called the proton-proton chain reaction. It releases a tremendous amount of energy, which powers the Sun and provides light and warmth to Earth.