Jack Steinberger, a Nobel Prize–winning scientist with a distinguished career in experimental physics, died December 12. He was 99.

Steinberger was most famous for his co-discovery of a new type of ghostlike particle called the muon neutrino—a breakthrough that earned him, Leon Lederman, and Melvin Schwartz the Nobel Prize in Physics in 1988. Steinberger studied the basic particles that make up the universe, and the elemental forces that govern their interactions, over a long scientific career that was jump-started by Enrico Fermi at the University of Chicago.