New results from an Italian space-based experiment have astronomers puzzled about the origins of cosmic rays. Cosmic rays are charged particles — protons and other atomic nuclei — that are accelerated to near-light speeds and continue on through the universe. The Earth is awash in them, with dozens of cosmic rays passing through your body every second of every day. Until now, the prevailing explanation for their origin was that they are accelerated by the remnants of supernovae, the spectacular final moments of dying high-mass stars. However, evidence gathered by the exquisitely sensitive Italian space-based instrument, called PAMELA, suggests this is not the case. It seems that different types of particles are accelerated in different ways, contrary to what is expected if they are accelerated by the same source.
It’s another entry in the “We didn’t expect that” file, which is part of what science is all about. And theorists always like the extra business.