Heliumkerne

Heliumkerne is used in astrophysics to denote the helium core of a star, formed after hydrogen burning in the core has ceased. In low- and intermediate-mass stars, the core contracts and heats until helium ignition occurs, often via the helium flash when the core is electron-degenerate; in more massive stars, helium ignites under non-degenerate conditions. The helium core mass at ignition in Sun-like stars is about 0.45–0.5 solar masses. Following ignition, helium burning proceeds mainly through the triple-alpha process, producing carbon and oxygen and releasing energy that alters the star’s structure. The presence and growth of the helium core drives the ascent of the red giant branch, and later evolutionary phases such as the horizontal branch or asymptotic giant branch, depending on the star’s mass and composition. The properties of the helium core influence luminosity, temperature, and the duration of subsequent evolutionary stages.

Heliumkerne also denotes the helium nucleus, or alpha particle, in nuclear physics. An alpha particle consists of two protons and two neutrons, bound together with a binding energy of about 28.3 MeV and a net electric charge of +2e. It is a primary product of radioactive decay and a key participant in stellar nucleosynthesis, notably in the triple-alpha process that builds carbon from helium. The helium nucleus behaves as a compact cluster within nuclei and is a standard probe in scattering experiments. In many contexts, the term Heliumkerne can refer to either the stellar helium core or the helium nucleus, with the intended meaning determined by the scientific setting.