Monday, January 24

Astronomers create the largest map of dark matter in the universe | Astronomy


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

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

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

Astronomers can map the existence of dark matter by observing the light that travels 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 analyze 100 m images of 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 one quarter of the sky in the southern hemisphere (one eighth of the total night sky visible from Earth).

Visualized as a pink, purple and black speckled patch, grouped within a pale ring (an overlay image of the Milky Way), the brightest areas of the map show the densest areas of dark matter, corresponding to superclusters of galaxies, while that the patches are cosmic voids (see main image).

Dr Niall Jeffrey from University College London, who co-led the project, said: “It shows us new parts of the universe that we have never seen before. We can actually see this cosmic lattice structure, including these huge 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 can behave very differently within them. Therefore, by identifying their shapes and locations, the map could provide a starting point for further study.

The map, to be published in the Monthly Notices of the Royal Astronomical Society., it 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 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 network.

Although the DES team’s calculations suggest that the distribution of this issue is broadly consistent with the predictions in the standard model, it is not a perfect fit. “If you look out into the universe, the matter is not as lumpy as expected, there are indications that it is softer,” Jeffrey said.

“It may seem like a relatively small thing, but if these suggestions are true, then it may mean that there is 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 what the universe should look like are not entirely correct, said co-author Professor Ofer Lahav, also from UCL and chairman of the DES UK consortium. Alternatively it may be a problem with the underlying model. “Some people would even pressure him to say that maybe Einstein was wrong,” he said.

Lahav isn’t ready to go that far yet: “What I’m saying is, ‘Look, don’t be too relaxed. There is something there that could indicate a disparity. Work hard, try to understand it through conventional means, but keep your eyes open because it could lead to a revolution in physics. “


www.theguardian.com

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