Every three hours, NASA’s Fermi Gamma-ray Space Telescope scans the entire sky, finding new types of gamma-ray-emitting objects including active galaxies, supernova remnants, globular star clusters, pulsars, and blazars. Each year, the Fermi team releases its second catalog of sources detected by the satellite’s Large Area Telescope (LAT), producing an inventory of close to 2,000 objects shining with the highest-energy form of light in the Universe.
“More than half of these sources are active galaxies, whose massive black holes are responsible for the gamma-ray emissions that the LAT detects,” said Gino Tosti, an astrophysicist at the University of Perugia in Italy and currently a visiting scientist at SLAC National Accelerator Laboratory in Menlo Park, Calif.
The Fermi Team discovered, for example, that that the Andromeda Galaxy [image below] “has fewer cosmic rays than our own Milky Way, probably because M31 forms stars — including those that die as supernovae, which help produce cosmic rays — more slowly than our galaxy,” according to Juergen Knoedlseder at the Research Institute for Astrophysics and Planetology in Toulouse, France. Currently a visiting scientist at the SLAC National Accelerator Laboratory.
The top five energy sources within our Milky Way are: