Very-High-Energy Gamma Rays from a Distant Quasar: How Transparent Is the Universe?

TL;DR

The MAGIC telescope detected very-high-energy gamma rays from a distant quasar, providing insights into the universe's transparency and the density of diffuse background light.

Contribution

First detection of very-high-energy gamma rays from a distant quasar, challenging previous assumptions about universe transparency at these energies.

Findings

Gamma rays from 3C 279 detected at >50 GeV

Universe's background light density is low enough to allow such gamma rays

Supports existing galaxy count estimates of diffuse background light

Abstract

The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Since high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.