Origin of cosmic rays is 'exploded stars'

Scientists have conclusive proof that many cosmic rays raining down on Earth come from distant exploded stars.

Cosmic rays - mostly ultra-fast proton particles - would threaten life if not for the shielding of our planet's atmosphere and magnetic field.

Nasa's Fermi telescope was used to study the very distinctive light that is produced when these protons crash into other particles in space.

This allowed researchers to trace their source directly to ancient supernovas.

The study was led by Dr Stefan Funk from Stanford University and the SLAC National Accelerator Laboratory.