Big Picture: High-energy eye to the sky

A new eye on the high-energy cosmos opened on Thursday 26 July. With a total area of 614 sq m, the Hess facility is the largest "Cherenkov telescope" ever made. It catches the light made when high-energy gamma rays hit the atmosphere, creating cascades of particles which briefly exceed the speed of light in air, giving hints about the rays' sources: supermassive black holes, pulsars and supernovae. Here, the gamma-ray sky over Namibia is superimposed on an image of one of Hess' dishes.