Largest ever Cherenkov telescope sees first light on 26th July

H.E.S.S. II, the largest Cherenkov telescope ever built, started its operation in Namibia on 26 July 2012.

Updated: Jul 27, 2012, 12:35 PM IST

Washington: H.E.S.S. II, the largest Cherenkov telescope ever built, started its operation in Namibia on 26 July 2012.

With its 28-meter-sized mirror, the telescope is dedicated to observing the most violent and extreme phenomena of the universe in very high energy gamma-rays.

Together with the four smaller (12 meter) telescopes already in operation since 2004, the H.E.S.S. (“High Energy Stereoscopic System”) observatory will continue to define the forefront of ground-based gamma ray astronomy and will allow deeper understanding of known high-energy cosmic sources such as supermassive black holes, pulsars and supernovae, and the search for new classes of high-energy cosmic sources.

With a mass of almost 600 tons and its 28-meter mirror -- the area of two tennis courts -- the new arrival is just huge.

H.E.S.S. II 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, marking the next big step in exploring the southern sky at gamma-ray energies.

“The new telescope not only provides the largest mirror area among instruments of this type worldwide, but also resolves the cascade images at unprecedented detail, with four times more pixels per sky area compared to the smaller telescopes,” stated Pascal Vincent from the French team responsible for the photo sensor package at the focus of the mirror.

Gamma rays are believed to be produced by natural cosmic particle accelerators such as supermassive black holes, supernovae, pulsars, binary stars, and maybe even relics of the Big Bang.

The universe is filled with these natural cosmic accelerators, impelling charged particles such as electrons and ions to energies far beyond what the particle accelerators built by mankind can reach. As high-energy gamma rays are secondary products of these cosmic acceleration processes, gamma ray telescopes allow us to study these high-energy sources.

Today, well over one hundred cosmic sources of very high-energy gamma rays are known. With H.E.S.S. II, processes in these objects can be investigated in superior detail, also anticipating many new sources, as well as new classes of sources. In particular, H.E.S.S. II will explore the gamma ray sky at energies in the range of tens of giga-electron-volts -- the poorly-explored transition regime between space-based instruments and current ground-based telescopes, with a huge discovery potential.

The most extreme gamma ray emitters -- active galactic nuclei -- shine in gamma rays with an apparent energy output which is one hundred times the luminosity of the entire Milky Way, yet the radiation seems to emerge from a volume much smaller than that of our solar system, and turns on and off in a matter of minutes, a strong signature of supermassive black holes. For some of the objects seen with the four H.E.S.S. telescopes in the last years, no counterpart at other wavelengths is known; they may represent a new type of celestial object that H.E.S.S. II will help to characterize.

“The successful commissioning of the new H.E.S.S. II telescope represents a big step forward for the scientists of H.E.S.S., for the astronomical community as a whole, and for Southern Africa as a prime location for this field of astronomy,” said Werner Hofmann, spokesperson of the project.

“H.E.S.S. II also paves the way to the realization of CTA -- the Cherenkov Telescope Array -- the next generation instrument ranked top priority by astroparticle physicists and funding agencies in Europe,” he added.

In a survey in 2006, H.E.S.S. was ranked the 10th most influential observatory worldwide, joining the ranks with the Hubble Space Telescope or the telescopes of the European Southern Observatory ESO in Chile.