An Etymological Dictionary of Astronomy and Astrophysics
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A class of → nuclear fusion reactions by which stars convert → helium into → heavy elements. Once carbon has been created, through → triple alpha process, in a star's interior, it can then continue to fuse with further → alpha particles to produce progressively heavier elements called → alpha particles. The first stage produces oxygen, followed by neon, magnesium, silicon, sulfur, argon, calcium, titanium, chromium and iron. This is known as the → alpha ladder, with energy released as a photon at each stage.

→ alpha;→ process.

A chain of nuclear fusion reactions by which three helium nuclei (→ alpha particles) are transformed into → carbon. First two nuclei of helium collide, fuse, and form a nucleus of → beryllium: ⁴He + ⁴He ↔ ⁸Be, which is unstable and will decay back into two helium nuclei within a few 10^-17 seconds. However, due to sufficiently high density and temperature in the stellar core, during a third collision between beryllium and helium, carbon is formed: ⁸Be + ⁴He → ¹²C + γ. The triple-alpha process is possible owing to the existence of the → Hoyle state. It is the main source of energy production in → red giants and → red supergiants in which the core temperature has reached at least 100 million K. Also called → Salpeter process.

→ triple; → alpha particle; → process.