© AIP Emilio Segrè Visual Archives, Physics Today Collection.
Fritz Zwicky discovered more of the exploding stars known as "supernovae" than all his predecessors combined. Zwicky's observations of supernovae in distant galaxies laid the foundation of his theoretical work. As he detected supernovae in ever-more distant galaxies, he realized that most galaxies combined in clusters. Careful measurements of the light from clusters led him to suggest the existence of dark matter. That may represent his greatest legacy, but he made other key contributions to astrophysics. He predicted the transition of ordinary stars into neutron stars and that galaxies could act as gravitational lenses. (Unit: 10)