Extreme universe uncovered by cosmic rays

A unique observatory in a remote location in Argentina is starting to unravel the mysteries of High Energy Cosmic Rays that shower the Earth at energies 10 million times higher than can be produced on Earth

The particles are still largely unknown to scientists, but the Pierre Auger Observatory is shedding new light on these energetic particles from space and using them as messengers to tell us more about the wider Universe.

"These highest-energy cosmic rays are messengers from the extreme universe," said Nobel Prize winner Jim Cronin, of the University of Chicago, who conceived the Auger experiment together with Alan Watson of the University of Leeds. "They represent a great opportunity for discoveries."

The observatory is constructing an array of 1600 detectors spread over 3000 square kilometres (an area roughly the size of Cambridgeshire) in Argentina's Mendoza Province, just east of the Andes Mountains. Each of these Cherenkov detectors contains 3000 gallons of water and detects the electromagnetic ‘shock waves’ as the particles pass through. Surrounding the array is a set of 24 telescopes which, on clear moonless nights, observe the ultraviolet fluorescence light produced as cosmic ray particles shower through the atmosphere.

One of 24 telescopes which detects fluorescence light produced by cosmic ray shower.

By tracking the ultra high energy particles back to their source the team hope to reach a consensus on the main mystery of the rays – where do they come from? “Once more science stands at the threshold of resolving a fundamental question that has so far eluded mankind - the source of high energy cosmic rays,” the Chief Executive of the UK's Particle Physics and Astronomy Research Council, Professor Keith Mason. “And I look forward with great interest to Auger's quest to unravel one of Nature's most intriguing mysteries."