oxygen burning

Oxygen burning is fusion of two oxygen nuclei, along with some subsequent reactions, which takes place in early stars, and produces silicon, phosphorus, sulfur, and magnesium. An oxygen-burning shell appears in a sufficiently-massive star during a phase while in the asymptotic giant branch (AGB). According to one common model, it forms after the neon-burning shell and before the silicon-burning shell (if the latter forms). Oxygen burns after neon because it requires a higher temperature (on the order of 10⁹ K): an oxygen nucleus is more stable and more kinetic energy is required to bring the nuclei together.