Scots shed new light on dark matter in a galaxy far, far away

ASTRONOMERS in Scotland have succeeded in mapping mysterious dark matter on the largest scale ever seen, revealing an intricate cosmic web of the invisible substance.

Dr Catherine Heymans from the University of Edinburgh and colleagues studied the way light emitted from distant galaxies bent as it passed massive clumps of dark matter on its way to Earth.

This enabled them to build up a map revealing complex structure made up of dark matter and galaxies spanning more than one billion light years.

Dark matter is believed to make up 90 per cent of the physical universe but cannot be detected directly. Scientists have no idea what it is made of, but know it exists because of its gravitational effect on galaxies.

Dark matter is believed to act as a “glue” that binds galaxies together. Without it, the universe would not exist in its present form.

Until now, most of what is known about dark matter has been based on computer simulations.

The team analysed images of about ten million galaxies in four different regions of the sky to watch how the light from these galaxies bent as it passed dark matter.

Their project, known as the Canada-France-Hawaii Telescope Lensing Survey, uses images collected over five years using a wide field imaging camera known as Megacam.

Galaxies included in the survey were typically six billion light years away.

The light captured by the images was emitted when the universe was six billion years old – roughly half the age it is today. This is the first direct glimpse at dark matter on large scales showing the cosmic web in all directions.

Dr Heymans, a physics and astronomy lecturer, said: “By analysing light from the distant Universe, we can learn about what it has travelled through on its journey to reach us.

“We hope that by mapping more dark matter than has been studied before, we are a step closer to understanding this material and its relationship with the galaxies in our universe.”

The results are being presented today to an American Astronomical Society meeting in Austin, Texas.

Professor Ludovic Van Waerbeke, from the University of British Columbia, who was also involved in the study, said: “It is fascinating to be able to ‘see’ the dark matter using space-time distortion. It gives us privileged access to this mysterious mass in the universe which cannot be observed otherwise.

“Knowing how dark matter is distributed is the very first step towards understanding its nature and how it fits within our current knowledge of physics.”

Images from the research show a network of gigantic dense (white) and empty (dark) regions.

The camera used by the team was a 340 megapixel camera attached to the Canada-France- Hawaii Telescope in Hawaii.

Over the next three years the team plans to image more than ten times the area mapped in this study, in order to better understand dark matter and its role in the universe.