Hans Albrecht Bethe
1906–2005, Strasbourg, German Empire (now France), Ithaca, New York, USA
German-American physicist who explained how stars produce energy through nuclear fusion — the proton-proton chain and the CNO cycle — and led theory at Los Alamos.
A student of Sommerfeld, Bethe wrote the encyclopedic 'Bethe bible' reviews of nuclear physics before fleeing Nazi Germany for Cornell in 1935. In 1938 he solved the long-standing problem of stellar energy, and during the war he headed the Theoretical Division at Los Alamos; afterward he made the first estimate of the Lamb shift, helping launch renormalized QED.
Nobel-winning work
Bethe's 1967 Nobel Prize honored 'his contributions to the theory of nuclear reactions, especially his discoveries concerning the energy production in stars'. In 1938–39 he showed that stars like the Sun fuse hydrogen into helium via the proton-proton chain, while heavier stars burn hydrogen through the CNO catalytic cycle, in which carbon, nitrogen and oxygen nuclei serve as catalysts.
The rates Bethe computed reproduced stellar luminosities and explained the solar neutrino flux, founding nuclear astrophysics: element abundances, stellar lifetimes and evolution all follow from these reaction networks.
Workplaces: Cornell University, Los Alamos National Laboratory
United States, Germany