The H.E.S.S. array of telescopes, located in Namibia and inaugurated in 2003, explores the upper end of the electromagnetic spectrum, by looking at very high energy gamma-rays coming from the cosmos. When very high energy photons produced in the Universe reach the Earth after a long journey, they interact in the upper atmosphere and generate a shower of very energetic particles. These particles, traveling faster than light in the atmosphere, emit faint and extremely brief flashes of blue light, called "Cherenkov radiation", which is captured by the very fast camera equipping the telescopes.
In the last 15 years, so called "Atmospheric Cherenkov Telescopes" have opened a new astronomical window, and discovered a unexpected rich zoo of both galactic and extra galactic very high energy gamma-ray emitters, belonging to the mysterious classes of pulsar wind nebulae, supernova remnants, active galactic nuclei, γ ray binaries and even more exotic ones.
H.E.S.S. was awarded the Descartes Prize for 2006 and Rossi Prize in 2010 in recognition of its numerous discoveries, and took an important part in the current emergence of multi-messenger, multi-wavelength astronomy that is currently revolutionizing our view on the High Energy Universe.
After a description of the Atmospheric Cherenkov technique and the H.E.S.S. instruments, I will take you on a journey through the Very High Energy Universe, presenting some of the most emblematic H.E.S.S. results and their physical interpretation.
Mathieu de Nauroi