Astronomers create largest map of the universe’s dark matter

International team reveal vast cosmic voids over the Earth’s skies that could challenge Einstein

We can’t see it, barely understand it, but know that it exists because of the powerful influence it exerts on space.

Dark matter makes up about 27% of the universe, and its gravitational force is enough to mesh entire galaxies together in a structure known as the cosmic web. Now, scientists have created the largest ever map of this mysterious substance – and it could imply that there’s something wrong with Einstein’s theory of relativity.

They have also mapped the location of vast cosmic voids where the conventional laws of physics may not apply.

Astronomers are able to map the existence of dark matter 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. Using artificial intelligence methods to analyse images of 100m galaxies, members of the international Dark Energy Survey (DES) team – a collaborative effort to reveal the nature of the mysterious dark energy that is driving the expansion of our universe – have created a map that covers a quarter of the sky of the southern hemisphere (an eighth of the total night sky visible from Earth).

Visualised as a pink, purple and black-mottled patch, clustered inside a pale ring (a superimposed image of the Milky Way), the brightest areas of the map show the densest areas of dark matter, corresponding to superclusters of galaxies, while the black patches are cosmic voids (see main image).

Map

Dr Niall Jeffrey, of University College London and École Normale Supérieure, Paris, who co-led the project, said: “It shows us new parts of the universe that we’ve never seen before. We can really see this cosmic web structure, including these enormous structures called cosmic voids, which are very low-density regions of the universe where there are very few galaxies and less matter.”

Scientists are interested in these structures because they suspect that gravity may behave very differently inside them. By identifying their shapes and locations, the map could therefore provide a starting point for further study.

The map, which will be published in the Monthly Notices of the Royal Astronomical Society, also brings us closer to understanding what the universe is made of and how it has evolved.

According to the standard model of cosmology, the universe started with the big bang, and then it expanded and matter evolved according to Einstein’s theory of general relativity, which describes gravity. These gravitational forces are what created the clumps and voids of matter, which constitute the cosmic web.

Although calculations by the DES team suggest that the distribution of this matter is broadly consistent with predictions in the standard model, it is not a perfect fit. “If you look out into the universe, the matter isn’t as clumpy as expected – there are hints that it is smoother,” said Jeffrey.

“It may seem a relatively small thing, but if these hints are true then it may mean there’s something wrong with Einstein’s theory of general relativity, one of the great pillars of physics.”

One possibility is that some of the measurements used to calculate how the universe should look are not quite right, said co-author Prof Ofer Lahav, also at UCL and chair of the DES UK consortium said. Alternatively, it may be a problem with the underlying model. “Some people would even push it to say maybe Einstein was wrong,” he said.

Lahav isn’t prepared to go that far himself, yet: “What I say is: ‘Look, don’t be too relaxed. There’s something there which might indicate a disparity. Work hard, try to understand it by conventional means, but keep your eyes open that it could lead to a revolution in physics.’

Contributor

Linda Geddes Science correspondent

The GuardianTramp

Related Content

Article image
Astronomers detect ‘cosmic bass note’ of gravitational waves
Sound comes from the merging of supermassive black holes across the universe, according to scientists

Hannah Devlin Science correspondent

29, Jun, 2023 @12:00 AM

Article image
Galaxy without any dark matter baffles astronomers
Scientists surprised to find NGC 1052-DF2 devoid of mysterious substance, but say its absence strengthens case for its existence

Hannah Devlin Science correspondent

28, Mar, 2018 @5:21 PM

Article image
Astronomers observe time dilation in early universe
Events appear to unfold five times slower when universe was a tenth of its present age, in effect predicted by Einstein

Ian Sample Science editor

03, Jul, 2023 @3:00 PM

Article image
Astronomers solve mystery of the universe’s missing stars
For more than a decade scientists have been at a loss to explain why there are fewer stars than they predicted

Stuart Clark

03, Dec, 2014 @7:48 PM

Article image
Rare sight for amateur astronomers as five planets align
Mercury, Venus, Mars, Jupiter and Saturn will be visible in order of their distance from the sun from Friday

Ian Sample Science editor

02, Jun, 2022 @6:00 AM

Article image
Euclid telescope prepares for voyage to create largest 3D map of the cosmos
European Space Agency’s €1bn probe will travel 1m miles from Earth to shed light on dark universe

Ian Sample Science editor

30, Jun, 2023 @11:42 AM

Article image
Astronomers find blinking giant star near heart of Milky Way
Huge star, 25,000 light years away, dims by 97% then slowly returns to former brightness

Ian Sample Science editor

11, Jun, 2021 @4:00 AM

Article image
Astronomers measure total starlight emitted over 13.7bn years
Stars have radiated 4x1084 photons since the universe begun with formation peaking 11bn years ago

Hannah Devlin Science correspondent

29, Nov, 2018 @11:27 PM

Article image
Astronomers spot first possible exoplanet outside our galaxy
Saturn-sized planet candidate has been identified in Whirlpool Galaxy 28m light years away

Linda Geddes Science correspondent

26, Oct, 2021 @12:16 PM

Article image
Third gravitational wave detection gives hints on dark matter and black holes
Latest observation by Ligo brings scientists closer to goal of using gravitational waves to see ancient events invisible to optical and radio telescopes

Hannah Devlin Science correspondent

01, Jun, 2017 @3:41 PM