What accelerates cosmic rays to nearly the speed of light? Astronomer have pondered that question for nearly 100 years, and now new evidence supports a theory held for two decades that cosmic rays likely are powered by exploding stars and stellar winds. "This discovery has been predicted for almost 20 years, but until now no instrument was sensitive enough to see it," said Wystan Benbow, an astrophysicist at the Smithsonian Astrophysical Observatory who coordinated this project for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) collaboration.
(...)
Read the rest of Solving the Mystery of Cosmic Rays' Origins (624 words)