Synthesis of carbon in a burning star. Two alpha particles react to form beryllium-. Beryllium- and an alpha particle react to form carbon-, proceeding via the Hoyle state. This state in carbon- is a “resonance” in the beryllium- plus alpha-particle system. Once the resonant state is formed, it tends to decay by breaking up into beryllium- and an alpha particle. However, approximately four out of ten thousand decays bring the excited carbon- nucleus to its stable ground state.