STOCKHOLM — Takaaki Kajita of Japan and Arthur McDonald of Canada won the Nobel Prize in physics today for the discovery of neutrino oscillations.

The Royal Swedish Academy of Sciences said the two researchers had made key contributions to experiments showing neutrinos change identities.

Neutrinos are particles that whiz through the universe at nearly the speed of light. They are created in nuclear reactions, such as in the sun and the stars, or in nuclear power plants.

“The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe,” the academy said.

Kajita, 56, is director of the Institute for Cosmic Ray Research and professor at the University of Tokyo. McDonald, 72, is a professor emeritus at Queen’s University in Kingston, Canada.

The winners will split the about $960,000 prize money. Each winner also gets a diploma and a gold medal.