Scientists have solved the mystery of cosmic rays, a stream of highly-energetic sub-atomic particles that pervades the Universe and is responsible for much of the extra radiation dose received by airline passengers.

Detailed observations of massive explosions in deep space have confirmed that cosmic rays emanate from exploding stars called supernovae which send out shock waves that accelerate the protons of cosmic rays to near the speed of light.

“The energies of these protons are far beyond what the most powerful particle colliders on Earth can produce,” said Stefan Funk, an astrophysicist with the Kavli Institute and Stanford University in California, who led the study

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“In the last century we've learned a lot about cosmic rays as they arrive here. We've even had strong suspicions about the source of their acceleration, but we haven't had unambiguous evidence to back them up until recently,” he said.

Using instrument on board the Fermi space telescope, the scientist observed the remnant of two supernovae explosions, one 5,000 light years away in the Gemini constellation, and one 10,000 light years away in the Aquila constellation.

They observed the characteristic signatures of the gamma radiation associated with cosmic rays, which they believe unambiguously confirms their origin in these exploding stars.

“Cosmic rays do influence the evolution of our galaxy - their combined total energy is similar to the energy in starlight in our galaxy - and we know where the star light originates - namely in stars,” Dr Funk said.

“We don't know, or have not known up to now, where the cosmic rays originate and this was one of the large unsolved puzzles about our Galaxy and our Universe,” he added.