Supernova Remnant Observations The sources of the cosmic rays that bombard Earth have been mysterious, but more recent explanations invoke high-energy acceleration of protons by the remnants of stellar explosions. Using the Fermi Large Area Telescope, Abdo et al. (p. 1103 , published online 5 January) obtained an image of the supernova remnant W44, which shows associated gamma-ray emissions in the order of gigaelectronvolts, conforming with models indicating local proton and nuclei acceleration