The sun doesn't burn — it fuses, and one physicist worked out exactly how

Stars generate their energy not by combustion but by fusing lighter atomic nuclei into heavier ones, releasing energy from the tiny loss of mass in the process. In 1939, physicist Hans Bethe published the specific chain reactions, the proton-proton chain and the CNO cycle, that explain how different stars sustain this fusion for billions of years. Bethe won the 1967 Nobel Prize in Physics for working out exactly how the sun keeps itself lit.

— Hans Bethe, Energy Production in Stars — Physical Review, 1939