Scientists have drawn up one of the most accurate matter maps of the universe, and it shows that there may be something missing in our best model of the cosmos.
Created by combining data from two telescopes that observe different types of light, the new map has revealed that the universe is less “lumpy” than previous models had predicted – a potential sign that the vast cosmic web that connects galaxies is less understood than scientists thought.
According to our current understanding, the cosmic web is a gigantic network of criss-crossing celestial highways paved with hydrogen gas and black matter. Taking shape in the chaotic aftermath of big Bang, the tendrils of the canvas formed like tufts of the bubbling broth of the young universe; where several strands of the web crossed, galaxies eventually formed. But the new map, released on January 31 as Three (opens in a new tab) separate (opens in a new tab) studies (opens in a new tab) in Physical Review D, shows that in many parts of the universe, matter is less clumped together and more evenly distributed than theory predicts.
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“There seems to be a little less fluctuation in the current universe than we would expect assuming our standard cosmological model is anchored to the early universe,” said co-author Eric Baxter, an astrophysicist at the University of Hawaii. said in a press release (opens in a new tab).
Weaving the cosmic web
According to the standard model of cosmology, the universe began to take shape after the Big Bang, when the young cosmos was teeming with particles of matter and antimatter, which arose to annihilate on contact. Most of the building blocks of the universe cleared out this way, but the rapidly expanding fabric of spacetime, along with some quantum fluctuations, caused some pockets of the primordial plasma to survive here and there.
The force of gravity quickly compressed these pockets of plasma into themselves, heating the matter as it was squeezed together so much that sound waves traveled at half speed. light (called baryonic acoustic oscillations) propagated outward from the plasma clusters. These undulations pushed the material that had not yet been sucked into the center of a tuft, where it came to rest in a halo around it. At that time, most of the matter in the universe was distributed as a series of thin films surrounding countless cosmic voids, like a nest of soap bubbles in a sink.
Once this material, mostly hydrogen and helium, cooled enough, it coagulated to give rise to the first stars, which, in turn, forged heavier and heavier elements through fusion. nuclear.
To map how the cosmic web was woven, the researchers combined observations taken with the Dark Energy Survey in Chile – which scanned the sky in near-ultraviolet, visible and near-infrared frequencies from 2013 to 2019 – and the South Pole Telescope, which is located in Antarctica and studies the microwave emissions that make up the cosmic microwave background – the oldest light in the universe.
Although they look at different wavelengths of light, both telescopes use a technique called gravitational lensing to map the clumping together of matter. Gravitational lensing occurs when a massive object is between our telescopes and its source; the more the light coming from a given pocket of space appears distorted, the more matter there is in that space. This makes gravitational lensing an excellent tool for tracking both normal matter and its mysterious cousin dark matter, which, despite making up 85% of the universe, only interacts with light by distorting it. with gravity.
With this approach, the researchers used data from both telescopes to locate matter and eliminate errors in one telescope’s data set by comparing it to the other.
“It works like a cross-check, so it becomes a much more robust measure than if you just used one or the other,” co-lead author Chihway Chang (opens in a new tab)an astrophysicist from the University of Chicago, said in the statement.
The map of cosmic matter produced by the researchers closely matched our understanding of the evolution of the universe, except for one key discrepancy: it was more evenly distributed and less clumped than the Standard Model of Earth suggested. cosmology.
There are two possibilities to explain this discrepancy. The first is that we are simply looking at the universe too imprecisely and that the apparent deviation from the model will disappear as we have better tools to peer into the cosmos. The second possibility, and the most important, is that our cosmological model lacks very important physics. Finding out which one is true will require more cross-investigation and mapping, as well as a deeper understanding of the cosmological constraints that bind the soap scum of the universe together.
“There is no known physical explanation for this discrepancy,” the researchers wrote in one of the studies. “Cross-correlations between surveys… will allow much more powerful cross-correlation studies that will provide some of the most precise and accurate cosmological constraints, and allow us to continue to stress test [standard cosmological] model.”
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