New map of all the matter in the universe reveals the cosmos is less “clumpy” than we thought

Making a new, more accurate map of all the matter in the universe – including all the visible matter as well as the elusive dark matter – has led astronomers to conclude that the universe is not as “clumpy” as previously thought, adding fuel to the thought that our Standard Model of the universe is incomplete.

Why does this matter?

Scientists believe that mapping out all the stars and galaxies formed by the matter that was flung out by the universe’s birth in the Big Bang about 13.7 billion years ago, can tell us about the forces that continue to shape the evolution of the cosmos.

The new map combines data from two major telescope surveys of the universe. The Dark Energy Survey was conducted over six years from a mountaintop in Chile. The South Pole Telescope is focused on finding faint traces of radiation left over from the first moments of the universe.

“It functions like a cross-check, so it becomes a much more robust measurement than if you just used one or the other,” says Chihway Chang, an assistant professor at the University of Chicago.

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Both surveys utilised gravitational lensing – a phenomenon that sees light bend as it passes by massive objects like galaxies.

Gravitational lensing captures both regular matter and dark matter.

According to the updated map of matter, the stuff in the universe is more spread out, rather than clustered into certain areas.

By overlaying maps of the sky from the Dark Energy Survey telescope (at left) and the South Pole Telescope (at right), the team could assemble a map of how the matter is distributed—crucial to understand the forces that shape the universe. Credit: Yuuki Omori.

That the universe is less “clumpy” than our current models suggest adds weight to the longstanding thought that there are forces at work in the cosmos that we are yet to fully grasp, or even completely unknown phenomena at work.

“It seems like there are slightly less fluctuations in the current universe, than we would predict assuming our standard cosmological model anchored to the early universe,” explains University of Hawaii assistant professor in astrophysics Eric Baxter.

The new map is the first to use information from two very different telescope surveys to peer into the void and glean information about the universe.

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“I think this exercise showed both the challenges and benefits of doing these kinds of analyses,” Chang adds. “There’s a lot of new things you can do when you combine these different angles of looking at the universe.”

If further mapping using other surveys of the night sky shows a similar deviation from what we would expect, then it is a sure sign that there remain great mysteries about how the universe is evolving.

The results are published in Physical Review D.

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