In today’s astrobite, we discuss the opacity of the Universe to high energy photons. The cosmic gamma-ray horizon, constrained by the authors of this paper, is a measure of this opacity, a cosmological probe and means of estimating blazar redshifts.
We think that blazars and gamma-ray bursts are both powered by extremely relativistic jets — but how is the kinetic energy of these jets transformed into the staggering amounts of radiation we observe?
What happens when a normally-dormant black hole at the center of a galaxy tears apart a passing star and burps it back out again in the form of a jet? The authors of this paper think that the Swift satellite has recently witnessed exactly this!