nickel56

Nickel-56 is a radioactive isotope of nickel with 28 protons and 28 neutrons. It has a mass of about 55.95 atomic mass units and a half-life of 6.075 days. Nickel-56 decays to cobalt-56 by beta-plus decay or electron capture, and cobalt-56 subsequently decays to iron-56 with a half-life of about 77.2 days. The decay chain releases gamma rays that are observable in astrophysical contexts.

In stellar environments, nickel-56 is produced during explosive silicon burning in both core-collapse and thermonuclear Type Ia supernovae. The synthesized Ni-56 then decays to Co-56 and Fe-56, providing a substantial source of energy that powers the early light curves of many supernovae. Observations of gamma-ray lines from Co-56 decay, notably at 847 keV and 1,238 keV, support the presence of Ni-56 in supernova ejecta.

The yield of Ni-56 varies by event; Type Ia supernovae typically produce around 0.5 solar masses of Ni-56, while core-collapse explosions generate smaller amounts, commonly in the range of about 0.01 to 0.15 solar masses. Because of its role in powering supernova luminosity, Ni-56 abundance is a key constraint in models of stellar explosions and galactic chemical evolution.

Natural nickel-56 is short-lived on astronomical timescales and is not found in significant amounts outside stellar environments; it is produced and destroyed in the interiors of stars and in supernovae.