Neutrinos may oscillate, or change from one kind to another, according to Bruno Pontecorvo’s theory. As more flavors of neutrinos were discovered over time, he continued to develop his theory (there was only one known type of neutrino when he first proposed the theory). Pontecorvo also predicted that supernovae, the massive explosions that occur when a star dies, would unleash a massive quantity of energy in the form of neutrinos.