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Lenses to Observe Dark Energy


July,2008

The Dark Energy Survey collaboration has reached a milestone in the construction of one of the largest ever cameras to detect dark energy by recieving five special lenses. This camera should bring scientists closer to detecting the invisible matter that cosmologists estimate makes up around 75% of our universe.

DES, Dark Energy Survey involves over a hundred scientists from the UK, US, Spain, and Brazil. The goal of DES is to map 300 million galaxies using the Blanco 4-meter telescope; this is a large telescope with new advanced optics, at Chile’s Cerro Tololo Inter-American Observatory. The pieces of glass have been shipped from the US to France, where they will be shaped and polished into their final form. The largest of the five lenses is one meter in diameter, making it one of the largest in the world.

Roughly 4% of the universe is made up from ordinary matter and 22% from dark matter; this leaves 74% unaccounted for – ‘dark energy’ which scientists claim to be the factor which drives the universe's accelerating expansion. The DES galaxy map should enable the astronomers to measure the dark energy far more precisely than current observations. Professor Ofer Lahav, head of the UCL Astrophysics Group, who also leads the UK DES Consortium, said: "Dark energy is one of the biggest puzzles in the whole of physics, going back to a concept proposed by Einstein 90 years ago. The DES observations will tell us if Einstein was right or if we need a major shift in our understanding of the universe.”

The glass for the five lenses was manufactured in the US before being shipped to France, where the lenses will be polished to a smoothness of one millionth of a centimeter. Unlike normal eye glasses, the task of polishing across such large lenses is far more demanding. "The polishing and assembly of the five DES lenses will be a major technological achievement, producing one of the largest cameras on Earth,” said Dr Peter Doel of the Optical Science Laboratory at UCL.

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