A 'web' of dark mater underneath the visible universe has been seen by scientists for the first time.
Dark matter is the counter-intuitive substance which makes up most of the mass of the universe, but which we are unable to see directly.
Most models of the universe suggest dark matter is abundant, and theories of its existence date back to the 1970s, when Vera Rubin noticed that stars near the edge of the galaxy move quicker than predicted.
The presence of large amounts of hidden matter across the universe would reconcile those observations with the laws of gravity.
But while astrophysicists have been working on experiments to demonstrate the existence of dark matter ever since, it remains mostly elusive.
Now astronomers say they have been able to take images of a network, or "cosmic web", mostly made up of dark matter, but using quasars as "cosmic flashlights".
A quasar is a pulsating, extremely bright galactic core. The presence of one of these ancient quasars near to a massive gas cloud two million light years wide gave scientists the opportunity to study the cloud in new detail. And by doing so, they were able to see 'filaments' of dark matter underlying the gas.
These filaments are left over from the original structure of the universe after the Big Bang. The theory roughly goes that most dark matter originally formed in 'halos', creating wells into which matter formed into galaxies. But most simulations show that some dark matter would be left over to 'bridge' the gaps between galaxies. This web of left-over dark matter is the filament observed in deep space.
The results were taken by using the 10-metre Keck telescope atop the Mauna Kea volcano in Hawaii, by researchers at the Max Planck Institute and the University of California.
Published in Nature, the study is the successful attempt to take an image of the spidery web-like structure of our universe.
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