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First Light for HESS II

HESS II or the new High Energy Spectrascopic System has started to make observations of very high energy gamma rays from it's base in Namibia.

The telescope uses the Cherenkov technique to detect gamma rays. As the gamma rays enter the upper atmosphere they travel at a speed that is faster than the speed of light in the atmosphere and therefore emit a shower of radiation. This does not violate the laws of physics because it is only the speed of light in a vacuum that cannot be surpassed. The speed of light through an optically dense medium is reduced by a factor equal to the refractive index of the material and it's possible for matter to travel at speeds between this reduced speed and the speed of light in a vacuum.

Together with four 12m dishes the new 28m detector will observe the most violent and extreme phenomena of the Universe from sources such as supermassive black holes, pulsars and supernovae.

The high plateaux of Southern Africa provide dark, clear skies with minimal atmospheric disturbance. Other world class telescopes in the region include the SALT or South African Large Telescope based at Sutherland in South Africa. This telescope is visited on Explorers South African Observatories tour in October 2013.