Very-High-Energy Gamma Rays from a Distant Quasar: How Transparent Is the Universe?
Journal - Science
The atmospheric Cherenkov gamma-ray telescope MAGIC, designedfor a low-energy threshold, has detected very-high-energy gammarays from a giant flare of the distant Quasi-Stellar Radio Source(in short: radio quasar) 3C 279, at a distance of more than5 billion light-years (a redshift of 0.536). No quasar has beenobserved previously in very-high-energy gamma radiation, andthis is also the most distant object detected emitting gammarays above 50 gigaelectron volts. Because high-energy gammarays may be stopped by interacting with the diffuse backgroundlight in the universe, the observations by MAGIC imply a lowamount for such light, consistent with that known from galaxycounts.* The complete list of authors and their affiliations appearsat the end of this paper. Present address: Santa Cruz Institute for Particle Physics,University of California, Santa Cruz, CA 95064, USA. Deceased.