Masatoshi Koshiba, professor emeritus at the University of Tokyo and doctoral graduate of the University of Rochester, won a share of the Nobel Prize in physics "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos." Two of this year's three Nobel Laureates in physics worked with neutrinos, some of the smallest and most elusive components of the universe, to expand our understanding of the very largest: the Sun, stars, galaxies and supernovae. The knowledge has changed the way we understand the cosmos.

"All I can say is I'm so happy," Koshiba told reporters after the announcement. "This wonderful outcome was only possible because of my young assistants' hard work."

He shares one half of the prize with another neutrino scientist, Raymond Davis Jr., of the University of Pennsylvania. (A third scientist, Riccardo Giacconi, of the Associated Universities Inc., won the other half of the prize in physics.)

Koshiba, who returned to Rochester in 2000 to receive a Distinguished Scholar Award, is the fifth Rochester alumnus to win a Nobel, and he is the eighth laureate with ties to the University. After receiving his doctorate in 1955, he became a professor of physics at the University of Tokyo until he retired in 1987. He is perhaps best known for masterminding the Kamiokande detector-a giant underground facility filled with water to catch the elusive neutrinos emitted from the sun, confirming our understanding of the nuclear reactions that power stars. His work helped launch a new field of research, neutrino-astronomy.

Koshiba has won international recognition in the form of the Wolf Prize from the president of Israel; Der grosse Verdienstkreutz from the president of West Germany; and the Order of Cultural Merit from the emperor of Japan. He is a member of the American Physical Society, Physical Society of Japan and Japanese Astronomical Society.

The Nobel Prizes, which are announced in a series each fall, are officially presented Dec. 10, in Stockholm, Sweden.