Stars rotate behind two of the five dishes that make up the High-Energy Stereoscopic Survey telescope (HESS) in Namibia. The dish at right, HESS II, spans about 90 feet, and was dedicated in September. The other is one of the four smaller dishes of HESS I. The telescopes look for brief flashes of blue light created when gamma rays strike particles in the upper atmosphere. These flashes of light can reveal details about the origin of the gamma rays, which are produced by some of the most powerful objects and events in the universe. [HESS Collaboration/Clementina Medina/Irfu-CEA]
Five telescopes rise from the Khomas Highland of Namibia like giant alien bugs. Their red steel structures look like exoskeletons, their multi-faceted mirrors like compound eyes, and their camera masts like sharp snouts. Also like some other-worldly creature, they see wavelengths of light that are invisible to the eyes of any living thing on Earth — wavelengths produced by some of the most powerful objects in the universe.
The telescopes form an array known as HESS — the High Energy Stereoscopic System. Four of the telescopes have main mirrors that span about 40 feet. The fifth, which was dedicated this fall, spans 90 feet.
HESS looks for Cherenkov radiation — flashes of blue light that occur when gamma rays strike particles high in Earth’s atmosphere. Seeing the flashes with more than one of the telescopes allows astronomers to track the gamma rays to their source. HESS is the largest Cherenkov detector in the world.
The gamma rays are byproducts of exploding stars, the black holes at the hearts of galaxies, and other powerful objects. Magnetic fields and shock waves in these environments accelerate particles to close to the speed of light. Interactions with the magnetic fields or with other particles cause them to emit gamma rays. Studying the Cherenkov radiation can help astronomers understand what’s going on around these exotic objects — an understanding made possible by some exotic telescopes.
Script by Damond Benningfield, Copyright 2012
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