Cosmic Ray Source Traced to Supernova Leftovers


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A new study has found that the leftover material from supernovas could be the source of mysterious cosmic rays.

The paper, to be published tomorrow in the journal Science, used data from NASA's Fermi Gamma-ray Space Telescope to examine the fast-moving particles and determine their origins.

"Scientists have been trying to find the sources of high-energy cosmic rays since their discovery a century ago," said Elizabeth Hays, a member of the research team and Fermi deputy project scientist at NASA's Goddard Space Flight Center. "Now we have conclusive proof supernova remnants, long the prime suspects, really do accelerate cosmic rays to incredible speeds."

Cosmic Rays are some of the fastest-moving particles ever detected. They are made up of subatomic particles such as electrons and atomic nuclei, though around 90% of them are protons. They travel at very close to light speed and are easily deflected by magnetic fields.

The Fermi Telescope was used to observe the IC443 (the Jellyfish Nebula) and W44 supernova remnants, where gamma rays are emitted by high-speed particles as they leave the remnants. Fermi researchers looked at four years of Fermi data and found that the gamma rays are a result of neutral pion particles, which are formed when cosmic rays (specifically the protons) hit non-cosmic ray protons.

"The discovery is the smoking gun that these two supernova remnants are producing accelerated protons," said Stefan Funk, the research team leader and an astrophysicist with the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University. "Now we can work to better understand how they manage this feat and determine if the process is common to all remnants where we see gamma-ray emission."