Zwicky, Fritz (tsvĭkˈē) [key], 1898–1974, Swiss-American astrophysicist, b. Bulgaria, educated at Zürich. Associated with the California Institute of Technology after his arrival in the United States in 1925, he became professor of astrophysics in 1942 and emeritus professor in 1972. He discovered more than 120 supernovas and with Rudolf Minkowski and Walter Baade he developed several models to explain their occurrence. Decades before the observational discovery of neutron stars, Zwicky suggested that the Crab Nebula in Taurus originated in a supernova. He is also known for his study of jet propulsion, cosmic rays, crystals, and slow electrons and ions in gases.