The Sun is powered by nuclear fusion. This is a process where hydrogen atoms are fused together to create helium, releasing a tremendous amount of energy in the process.

Here's how it works:

1. Extreme pressure and heat: The Sun's immense gravity creates incredible pressure and heat in its core.

2. Hydrogen nuclei collide: The intense heat causes the hydrogen nuclei (protons) to move extremely fast, overcoming their electrical repulsion and colliding with each other.

3. Fusion: Occasionally, two hydrogen nuclei collide with enough force to overcome their natural repulsion and fuse together, forming a deuterium nucleus (one proton and one neutron).

4. Energy release: This fusion process releases a massive amount of energy in the form of gamma rays and neutrinos.

5. Chain reaction: The deuterium then fuses with another proton to form a helium-3 nucleus, releasing more energy. Finally, two helium-3 nuclei fuse to create a helium-4 nucleus, releasing even more energy.

This continuous cycle of fusion reactions is what powers the Sun, providing the light and heat that sustains life on Earth.