extragalactic background light

An international group of researchers has developed a new way to measure accurately the extragalactic background light (EBL) that fills the universe. The technique involves measuring the attenuation of high-energy gamma rays from distant blazars and it could improve our understanding of how galaxies form and evolve, as well as how the universe has expanded since the Big Bang

2013 March 27, Tushna Commissariat, “Blazars help measure extragalactic background light”, in PhysicsWorld

Ground-based observatories have been collecting 0.2 - 20 TeV gamma rays from blazars for about twenty years. These gamma rays can experience absorption along the line of sight due to interactions with the extragalactic background light (EBL). In this paper, we show that the gamma-ray optical depth can be reduced to the convolution product of an EBL kernel with the EBL intensity, assuming a particular form for the EBL evolution

2015, Jonathan Biteau, David A. Williams, "The extragalactic background light, the Hubble constant, and anomalies: conclusions from 20 years of TeV gamma-ray observations", arXiv; (1502.04166) [14 February 2015]