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Astronomers have created the largest ever map of dark matter

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The map shows the pattern of dark matter in the universe

N. Jeffrey/Dark Energy Survey collaboration

Researchers have created the largest ever map of dark matter, the invisible material thought to account for 80 per cent of the total matter in the universe.

As matter curves space-time, astronomers are able to map its existence by looking at light travelling to Earth from distant galaxies. If the light has been distorted, this means there is matter in the foreground, bending the light as it comes towards us.

The Dark Energy Survey (DES) team used artificial intelligence to analyse images of 100 million galaxies, looking at their shape to see if they have been stretched. The new map, pictured above, is a representation of all matter detected in the foreground of the observed galaxies and covers a quarter of the southern hemisphere’s sky.

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Niall Jeffrey at University College London, part of the DES team, says: “Most of the matter in the Universe is dark matter. It is a real wonder to get a glimpse of these vast, hidden structures across a large portion of the night sky.”

“In our map, which mainly shows dark matter, we see a similar pattern as we do with visible matter only, a web-like structure with dense clumps of matter separated by large empty voids,” he said. “Observing these cosmic-scale structures can help us to answer fundamental questions about the universe.”

For decades astronomers have suspected there is more material in the universe than we can see. Dark matter, like dark energy, remains mysterious, but its existence is inferred from galaxies behaving in unpredicted ways. For instance, the fact that galaxies stay clustered together, and that galaxies within clusters move faster than expected.

Ofer Lahav at UCL and also part of the DES team says: “Visible galaxies form in the densest regions of dark matter. When we look at the night sky, we see the galaxy’s light but not the surrounding dark matter, like looking at the lights of a city at night. By calculating how gravity distorts light, a technique known as gravitational lensing, we get the whole picture, both visible and invisible matter.”

New analysis of the first three years of the survey by DES scientists suggests matter is distributed throughout the universe in a way that is consistent with predictions in the standard cosmological model, the best current model of the universe. But researchers also found hints, as with previous surveys, the universe may be a few per cent smoother than predicted.

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