Space camera zooms in on dark energy riddle

Astronomers believe they may be on course to crack the mystery of one of the Universe’s dark forces thanks to a powerful new space camera that has just come into operation.

This Dark Energy Camera, which has a mind-boggling 570 million pixels, will begin to survey the sky from Chile in incredible detail in December after taking its first picture on 12 September. Each of its snapshots will be able to capture more than 100,000 distant galaxies up to 8 billion light-years away.

Fitted to the Blanco telescope with its 3.6 metre (13ft) mirror, the camera’s 62 detectors are especially sensitive to faint red light. It will help produce a 3D map of how galaxies are spread across the cosmos, showing their shapes and how they are moving in space.

Scientists hope that will help them learn more about dark energy, a force that is still a complete mystery. In the 1990s it was confirmed that the Universe is not just expanding but that the rate at which it is expanding is speeding up.

The force believed responsible for this acceleration is thought to account for 75 per cent of the energy-mass of the Universe, so it may seem rather surprising that we can know so little about it.

It stands as a riddle alongside dark matter which, despite its similar name, is not thought to be related. Gravitational effects on galaxies show there is up to ten times as much dark matter as normal matter in the Universe, but astronomers are pretty clueless about that too!

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As well as producing a Dark Energy Survey (DES), the camera, which is the size of a phone booth, will study our closer neighbours, the asteroids. But for its main work, it will study galaxy clusters, supernovae, the large-scale clumping of galaxies, and weak gravitational lensing. This will be the first time all four of these methods will be possible in a single experiment.

Led by Fermilab in the USA, the DES is also supported by the UK, Spain, Brazil, Germany, and Switzerland. Professor Will Percival, of Portsmouth University in the UK, will co-coordinate the galaxy clustering project. He said: “This will be the largest galaxy survey of its kind, and the galaxy shapes and positions will tell us a great deal about the nature of the physical process that we call Dark Energy, but do not currently understand.”

Professor Richard McMahon, University of Cambridge, said: “The construction of a 3-dimensional map of the galaxies just based on their positions and optical colours is extremely challenging and will require sophisticated computational and statistical techniques. The addition of galaxy near infrared colours from another UK led sky mapping survey, the VISTA Hemisphere Survey, will greatly improve the accuracy of the map”.