[unable to retrieve full-text content]
[unable to retrieve full-text content]
A team of scientists, comprising experts from the University of Chicago and Fermi National Accelerator Laboratory, have made a game-changing announcement with their release of one of the most accurate measurements to date of the universe’s matter distribution.
Sometimes to know what the matter is, you have to find it first.
When the universe began, matter was flung outward and gradually formed the planets, stars, and galaxies that we know and love today. By carefully assembling a map of that matter today, scientists can try to understand the forces that shaped the evolution of the universe.
A group of scientists, including several with the University of Chicago and Fermi National Accelerator Laboratory, have released one of the most precise measurements ever made of how matter is distributed across the universe today.
Combining data from two major telescope surveys of the universe, the Dark Energy Survey and the South Pole Telescope, the analysis involved more than 150 researchers and is published as a set of three articles on January 31 in the journal Physical Review D.
Among other findings, the analysis indicates that matter is not as “clumpy” as we would expect based on our current best model of the universe, which adds to a body of evidence that there may be something missing from our existing standard model of the universe.
Scientists have released a new survey of all the matter in the universe, using data taken by the Dark Energy Survey in Chile and the South Pole Telescope. Credit: Photo by Andreas Papadopoulos
After the Big Bang created all the matter in the universe in a very hot, intense few moments about 13 billion years ago, this matter has been spreading outward, cooling and clumping as it goes. Scientists are very interested in tracing the path of this matter; by seeing where all the matter ended up, they can try to recreate what happened and what forces would have had to have been in play.
The first step is collecting enormous amounts of data with telescopes.
In this study, scientists combined data from two very different telescope surveys: The Dark Energy Survey, which surveyed the sky over six years from a mountaintop in Chile, and the South Pole Telescope, which looks for the faint traces of radiation that are still traveling across the sky from the first few moments of the universe.
The South Pole Telescope is part of a collaboration between Argonne and a number of national labs and universities to measure the CMB, considered the oldest light in the universe. The high altitude and extremely dry conditions of the South Pole keep water vapor from absorbing select light wavelengths. Credit: Image by Argonne National Laboratory
Combining two different methods of looking at the sky reduces the chance that the results are thrown off by an error in one of the forms of measurement. “It functions like a cross-check, so it becomes a much more robust measurement than if you just used one or the other,” said UChicago astrophysicist Chihway Chang, one of the lead authors of the studies.
In both cases, the analysis looked at a phenomenon called gravitational lensing. As light travels across the universe, it can be slightly bent as it passes objects with lots of gravity, like galaxies.
This method catches both regular matter and dark matter—the mysterious form of matter that we have only detected due to its effects on regular matter—because both regular and dark matter exert gravity.
By rigorously analyzing these two sets of data, the scientists could infer where all the matter ended up in the universe. It is more precise than previous measurements—that is, it narrows down the possibilities for where this matter wound up—compared to previous analyses, the authors said.
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: Image courtesy of Yuuki Omori
The majority of the results fit perfectly with the currently accepted best theory of the universe.
But there are also signs of a crack—one that has been suggested in the past by other analyses, too.
“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,” said analysis coauthor and University of Hawaii astrophysicist Eric Baxter (UChicago PhD’14).
That is, if you make a model incorporating all the currently accepted physical laws, then take the readings from the beginning of the universe and extrapolate it forward through time, the results look slightly different from what we actually measure around us today.
“There’s a lot of new things you can do when you combine these different angles of looking at the universe.”
— Chihway Chang, UChicago astrophysicist
Specifically, today’s readings find the universe is less “clumpy”—clustering in certain areas rather than evenly spread out—than the model would predict.
If other studies continue to find the same results, scientists say, it may mean there is something missing from our existing model of the universe, but the results are not yet to the statistical level that scientists consider to be ironclad. That will take further study.
However, the analysis is a landmark as it yielded useful information from two very different telescope surveys. This is a much-anticipated strategy for the future of astrophysics, as more large telescopes come online in the next decades, but few had actually been carried out yet.
“I think this exercise showed both the challenges and benefits of doing these kinds of analyses,” Chang said. “There’s a lot of new things you can do when you combine these different angles of looking at the universe.”
University of Chicago Kavli Associate Fellow Yuuki Omori was also a lead co-author for the papers. The full studies and authorships, “Joint analysis of Dark Energy Survey Year 3 data and CMB lensing from SPT and Planck,” can be found in three papers selected as the editor’s suggestion at Physical Review D.
References:
“Joint analysis of Dark Energy Survey Year 3 data and CMB lensing from SPT and Planck. I. Construction of CMB lensing maps and modeling choices” by Y. Omori et al. (DES and SPT Collaborations), 31 January 2023, Physical Review D.
DOI: 10.1103/PhysRevD.107.023529
“Joint analysis of Dark Energy Survey Year 3 data and CMB lensing from SPT and Planck. II. Cross-correlation measurements and cosmological constraints” by C. Chang et al. (DES & SPT Collaborations), 31 January 2023, Physical Review D.
DOI: 10.1103/PhysRevD.107.023530
“Joint analysis of Dark Energy Survey Year 3 data and CMB lensing from SPT and Planck. III. Combined cosmological constraints” by T. M. C. Abbott et al. (DES and SPT Collaborations), 31 January 2023, Physical Review D.
DOI: 10.1103/PhysRevD.107.023531
The South Pole Telescope is primarily funded by the National Science Foundation and the Department of Energy and is operated by a collaboration led by the University of Chicago. The Dark Energy Survey was an international collaboration coordinated through Fermi National Accelerator Laboratory and funded by the Department of Energy, the National Science Foundation, and many institutions around the world.
Article From & Read More ( Cosmic Breakthrough: Accurate New Map of All the Matter in the Universe Released - SciTechDaily )
Scientists have made one of the most precise maps of the universe's matter, and it shows that something may be missing in our best model of the cosmos.
Created by pooling data from two telescopes that observe different types of light, the new map revealed that the universe is less "clumpy" than previous models 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 crisscrossing celestial superhighways paved with hydrogen gas and dark matter. Taking shape in the chaotic aftermath of the Big Bang, the web's tendrils formed as clumps from the roiling broth of the young universe; where multiple strands of the web intersected, galaxies eventually formed. But the new map, published Jan. 31 as three (opens in new tab) separate (opens in new tab) studies (opens in new tab) in the journal Physical Review D, shows that in many parts of the universe, matter is less clumped together and more evenly spread out than theory predicts it should be.
Related: How dark is the cosmic web?
"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," co-author Eric Baxter, an astrophysicist at the University of Hawaii, said in a statement (opens in new tab).
According to the standard model of cosmology, the universe began taking shape after the Big Bang, when the young cosmos swarmed with particles of both matter and antimatter, which popped into existence only to annihilate each other upon contact. Most of the universe's building blocks wiped themselves out this way, but the rapidly expanding fabric of space-time, along with some quantum fluctuations, meant that some pockets of the primordial plasma survived here and there.
The force of gravity soon compressed these plasma pockets in on themselves, heating the matter as it was squeezed closer together to such an extent that sound waves traveling at half the speed of light (called baryon acoustic oscillations) rippled outward from the plasma clumps. These ripples pushed away the matter that hadn't already been drawn into the center of a clump, where it came to rest as a halo around it. At that point, most of the universe's matter was distributed as a series of thin films surrounding countless cosmic voids, like a nest of soap bubbles in a sink.
Once this matter, primarily hydrogen and helium, had sufficiently cooled, it clotted further to birth the first stars, which, in turn, forged heavier and heavier elements through nuclear fusion.
To map out how the cosmic web was spun, the researchers combined observations taken with the Dark Energy Survey in Chile — which scanned the sky in the 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.
Though they look at different wavelengths of light, both telescopes use a technique called gravitational lensing to map the clumping of matter. Gravitational lensing occurs when a massive object sits between our telescopes and its source; the more that light coming from a given pocket of space appears warped, 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, doesn't interact with light except by distorting it with gravity.
With this approach, the researchers used data from both telescopes to pinpoint the location of matter and weed out errors from one telescope's data set by comparing it to the other's.
"It functions like a cross-check, so it becomes a much more robust measurement than if you just used one or the other," co-lead author Chihway Chang (opens in new tab), an astrophysicist at the University of Chicago, said in the statement.
The cosmic matter map the researchers produced closely fitted our understanding of how the universe evolved, except for a key discrepancy: It was more evenly distributed and less clumped than the standard model of cosmology would suggest.
Two possibilities exist to explain this discrepancy. The first is that we're simply looking at the universe too imprecisely, and that the apparent deviation from the model will disappear as we get better tools to peer at the cosmos with. The second, and more significant, possibility is that our cosmological model is missing some seriously big physics. Finding out which one is true will take more cross-surveys and mappings, as well as a deeper understanding of the cosmological constraints that bind the universe's soap suds.
"There is no known physical explanation for this discrepancy," the researchers wrote in one of the studies. "Cross-correlations between surveys … will enable significantly more powerful cross-correlation studies that will deliver some of the most precise and accurate cosmological constraints, and that will allow us to continue stress-testing the [standard cosmological] model."
Article From & Read More ( New map of the universe's matter reveals a possible hole in our understanding of the cosmos - Livescience.com )
