What nuclear reaction occurs in stars?

In stars, the primary nuclear reaction is nuclear fusion, where lighter atomic nuclei combine to form heavier nuclei, releasing vast amounts of energy. The most common fusion process in stars like the Sun is the conversion of hydrogen into helium through a series of reactions known as the proton-proton chain. This reaction releases energy in the form of light and heat, which powers the star and contributes to the processes that sustain life on Earth. In more massive stars, other fusion processes can occur, including the fusion of helium into heavier elements.