A huge effort to map dark matter across the cosmos has released its first data.
Dark matter is the invisible “web” that holds galaxies together; by watching how clumps of it shift over time, scientists hope eventually to quantify dark energy – the even more mysterious force that is pushing the cosmos apart.
The map will eventually span one-eighth of the sky; this first glimpse covers just 0.4%, but in unprecedented detail.
It shows fibres of dark matter, studded with galaxies, and voids in between.
The international collaboration, known as the Dark Energy Survey (DES), will present its preliminary findings on Tuesday at a meeting of the American Physical Society and publish them on the Arxiv preprint server.
The survey involves more than 300 scientists from six countries and uses images taken by one of the best digital cameras in the world: a 570-megapixel gadget mounted on the Victor Blanco telescope at the Cerro Tololo Inter-American Observatory, high in the Chilean Andes.
Incredible detail is required to detect dark matter, based purely on the way it warps the light from very distant galaxies.
Mapping the invisible
“Our goal all this time has been to see the invisible – to see dark matter,” said Sarah Bridle, an astrophysics professor at the University of Manchester and co-chair of the DES weak lensing group, which produced the map.
“To be able to look at a map and say, ‘That part of the sky’s got more dark matter in it, that bit’s empty,’ is the dream that we’ve had all this time,” Prof Bridle told the BBC.
“It’s been a long time coming.”
The survey commenced more than two years ago and will run for another three. This preliminary map was made using data from the camera’s very first test images.
“We were testing out the quality of the camera,” Prof Bridle explained.
“It takes a very, very long time to process all of this data and do the analysis. We’re currently looking at more data and eventually we’re going to have a map 30 times this size.”
Even this preliminary effort is something of a landmark.
“This is the largest contiguous dark matter map that’s been made,” Prof Bridle said.
An earlier series of four images covered a bigger swathe of sky but the images did not overlap and had nowhere near the detail of the DES.
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SOURCE: BBC, Jonathan Webb
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