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Tuesday, November 13, 2012

Using Quasars to Map the Impact of Dark Energy

Scientists have used a novel technique to probe the nature of dark energy some 10 billion years into the past.

They hope it will bring them closer to an explanation for the strange force that appears to be driving the Universe apart at an accelerating rate.

The method relies on bright but distant objects known as quasars to map the spread of hydrogen gas clouds in space.

The 3D distribution of these clouds can be used as a tracer for the influence of dark energy through time.

A scholarly paper describing the approach has been submitted to the journal Astronomy & Astrophysics and posted on the arXiv.org preprint site.

It is authored by the BOSS (Baryon Oscillation Spectroscopic Survey) team, which uses the 2.5m Sloan Foundation Telescope in New Mexico, US, to make its observations of the sky.

The international group's new data is said to be a very neat fit with theory, confirming ideas that dark energy did not have a dominant role in the nascent Universe. Back then, gravity actually held sway, decelerating cosmic expansion. Only later did dark energy come to the fore.

"We know very little about dark energy but one of our ideas is that it is a property of space itself - when you have more space, you have more energy," explained Dr Matthew Pieri, a BOSS team-member.

"So, dark energy is something that increases with time. As the Universe expands, it gives us more space and therefore more energy, and at some point dark energy takes over from gravity to end the deceleration and drive an acceleration," the Portsmouth University, UK, researcher told BBC News.

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