New eye sweeps the gamma sky

End of July, the four 12 meter-telescopes of the H.E.S.S. observatory (High Energy Stereoscopic System), dedicated to investigating cosmic gamma-rays in Namibia, received reinforcement: The new telescope H.E.S.S. II has a 28-meter-sized mirror and is therefore the largest Cherenkov telescope ever built. With such telescopes, researchers observe the most violent and extreme phenomena of the Universe in very high energy gamma-rays. The University of Tübingen is part of the international H.E.S.S. collaboration, which builds and runs the telescopes, through the High Energy Astrophysics Section of the Institute for Astronomy and Astrophysics Tübingen (IAAT), financially supported by the Federal Ministry for Education and Research.

Today, scientists know well over one hundred cosmic sources of very high-energy gamma rays. With the new instrument near the Gamsberg in Namibia, the astrophysicists not only want to investigate these objects in superior detail, but also detect many new sources. The researchers hope for a deeper understanding of known high-energy cosmic sources such as supermassive black holes, pulsars and supernovae, but also to detect new classes of high-energy cosmic sources.

The new telescope has a mass of almost 600 tons, and its 28-meter mirror corresponds to the area of two tennis courts. It saw its first light at 0:43 a.m. (German time zone) on 26 July 2012, detecting its very first images of atmospheric particle cascades generated by cosmic gamma rays and by cosmic rays. "The new telescope resolves the cascade images at unprecedented detail, with four times more pixels per sky area compared to the smaller telescopes" states Dr. Pascal Vincent from the French team responsible for the photo sensor package (camera) at the focus of the mirror.

The astrophysicists from Tübingen collaborated with the Max-Planck-Institute for Nuclear Physics Heidelberg and Polish groups to provide the machinery that supports and aligns all 875 individual mirror facets. Those finally form the telescope's reflecting surface. "The sheer amount of individual parts was a challenge for the institute" states Gerd Pühlhofer who is coordinating the institute's high energy gamma-ray activities. "Not only did we design and produce the electronics and software for the mirror alignment system. We also equipped all 1750 actuators, that is the mirror alignment units, with our electronics, tested them, shipped them to Namibia and mounted them at the telescope. In addition, also all glass mirror facets went through our institute, for quality tests in our 70m testing ground in the basement of our institute, amongst other things."

"A lot of our workshop people, students, and scientists worked hard and tirelessly to get this done" says Prof. Dr. Andrea Santangelo, leader of the High Energy Astrophysics Section at IAAT. "Also at the preparation of the next generation of telescopes, the Cherenkov Telescope Array CTA, the University of Tübingen is strongly involved in the development of this exciting branch of astroparticle physics."