... Credit: NASA , DOE , International Fermi LAT Collaboration Explanation: What shines in the gamma-ray sky? The most complete answer yet to that question is offered by the Fermi Gamma-ray Space Telescope's first all-sky catalog . Fermi's sources of cosmic gamma-rays feature nature's most energetic particle accelerators , ultimately producing 100 MeV to 100 GeV photons, photons with more than 50 million to 50 billion times the energy of visible light . ... NASA Official: Jay Norris. ...