The German-American physicist who explained how stars produce energy through nuclear fusion — winning the 1967 Nobel Prize for discovering the proton–proton chain and CNO cycle.
Hans Albrecht Bethe (2 July 1906 – 6 March 2005) was born in Strasbourg, Alsace-Lorraine (then Germany). He earned his doctorate from the University of Munich in 1928 under Arnold Sommerfeld. Dismissed from his post at Tübingen in 1933 under Nazi racial laws, he emigrated to the United States and joined Cornell University in 1935, where he remained for the rest of his career.[1]
In 1938, with Charles Critchfield, Bethe described the proton–proton chain — the process by which hydrogen fuses into helium in stars like the Sun. In 1939, he independently worked out the carbon–nitrogen–oxygen (CNO) catalytic cycle that dominates in more massive stars.[2]
Bethe’s three comprehensive 1936–1937 review articles on nuclear physics in Reviews of Modern Physics, known as “Bethe’s Bible,” became the standard reference for a generation. During World War II he headed the Theoretical Division at Los Alamos.[3]
After the war, Bethe became a prominent advocate for nuclear arms control and test-ban treaties. He publicly opposed the hydrogen bomb program and later advocated for the Comprehensive Nuclear-Test-Ban Treaty. He died in Ithaca, New York, on 6 March 2005, at age 98.[4]