The Third EGRET Catalog -- the positions of all known gamma ray sources in the Universe at energies greater than 100 MeV. (MeV is one million electron volts; the energy of a photon of visible light is about 2-3 electron volts.) Green dots show a concentration of unknown gamma-ray sources in the Milky Way and above the galactic plane. Red diamonds show active galactic nuclei scattered throughout the Universe. The blue dot at -180 degrees represents the great 1991 solar flare, and thus shows the location of our Solar System on the all-sky map.
CREDIT: The EGRET team, NASA/GSFC, using the Energetic Gamma Ray Experiment Telescope on the Compton Gamma Ray Observatory. Compiled from data from 1991-1995.
