A 2002 Nobel Prize in physics for work that revolutionized our understanding of how the sun generates energy will be awarded to Raymond Davis Jr., 87.

Davis, research professor of physics at Penn and research collaborator at Brookhaven National Laboratory, was the first to detect neutrinos, ghostlike particles produced in solar nuclear reactions. His work, which found only one-third the number of predicted neutrinos, sent astrophysicists into a mad search for the missing particles.

“This experiment started a whole new field of science,” said Kenneth Lande, a Penn professor of physics.

Subsequent experiments, which involved Penn collaboration, solved the mystery. Lande, who started working with Davis in the 1970s, said the recent discovery that some electron neutrinos produced in solar fusion reactions were being converted into other neutrino species was “totally unexpected.”

This is the Physics Department’s fourth Nobel Prize.

Davis shares his Nobel Prize with Masatoshi Koshiba of the University of Tokyo and Riccardo Giacconi of Associated Universities Inc. in Washington.