Fermi Gamma-ray Observatory

Fermi’s Large Area Telescope (LAT) mapped billion-electron-volt (GeV)
gamma rays from three middle-aged supernova remnants -- known as W51C,
W44, and IC 443 -- that were never before resolved at these energies.
(The energy of visible light is between 2 and 3 electron volts.) Each
remnant is the expanding debris of a massive star that blew up between
4,000 and 30,000 years ago.

In 1949, the Fermi telescope’s namesake, physicist Enrico Fermi,
suggested that the highest-energy cosmic rays were accelerated in the
magnetic fields of gas clouds. In the decades that followed,
astronomers showed that supernova remnants are the galaxy’s best
candidate sites for this process.

http://svs.gsfc.nasa.gov/vis/a010000/a010500/a010566/index.html