Dark matter's cosmic web revealed
Astronomers have mapped dark matter for the first time on the largest scale ever observed.
Edinburgh astronomers studied the way light emitted from 10 million galaxies was bent as it passed massive clumps of dark matter on its journey to Earth.
They found web-like strands of dark matter stretching in all directions.
Dark matter is believed to make up 90% 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 new study, presented at the annual meeting of the American Astronomical Society in Austin, Texas, provides the first "real" glimpse of dark matter at cosmic scales.
Dr Catherine Heymans, from Edinburgh University, 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."
Light years away
Professor Ludovic Van Waerbeke, of the University of British Columbia in Canada, 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."
The international project involved studying images collected over a period of five years by the Canada-France-Hawaii Telescope (CFHC) on Mauna Kea mountain in Hawaii.
Galaxies included in the survey were typically six billion light years away.
They emitted their light when the universe was six billion years old, roughly half the age it is today.