Born on this day in 1926 in Toyohashi, Japan, Masatoshi Koshiba is an astrophysicist who shared the 2002 Nobel Prize in Physics for pioneering the field of neutrino astronomy. Koshiba earned a PhD in physics at the University of Rochester in 1955. He returned to Japan in 1958. Around 1980 Koshiba and other particle physicists became interested in detecting the exceedingly rare decay of a proton into a neutral pion and a positron. Koshiba led the design of a massive underground detector, Kamiokande, that could detect the Cherenkov radiation produced by the decay products. Koshiba realized that his detector could also detect solar neutrinos, whose flux was puzzlingly lower than predicted. He and his team modified their experiment. When, in February 1987, a nearby supernova burst in the sky, Kamiokande II was up and running. The 12 neutrinos it detected from the supernova were the first ever detected on Earth from outside the solar system. (Photo credit: AIP Emilio Segrè Visual Archives)