Beyond Einstein: Groundbreaking map of the universe redefines cosmic models

of HOWEVER collaboration is examining the accelerating expansion of the universe through comprehensive mapping from its earliest stages to the present day. Their findings challenge traditional cosmic models and suggest new insights into dark energy, all using innovative and unbiased research methods.

A team of researchers, including an astrophysicist from the University of Texas at Dallas, as part of the Dark Energy Spectroscopic Instrument (DESI) collaboration, is leading a groundbreaking experiment aimed at exploring the expansion and acceleration of the universe.

Dr. Mustapha Ishak-Boushaki, professor of physics in the School of Natural Sciences and Mathematics (NSM) at UT Dallas, is a member of the DESI collaboration, an international group of more than 900 researchers from over 70 institutions worldwide engaged in an experiment perennial to increase understanding of the history and fate of the cosmos.

On April 4, Ishak-Boushaki presented analyzes of the first year of data collected by the DESI experiment at a meeting of the American Physical Society in Sacramento, California, along with two other DESI scientists. Ishak-Boushaki presented the cosmological results derived from the DESI data and their implications for the universe. The researchers also shared results from the first year of data collected in multiple papers posted on the arXiv preprint site.

The role of the DESI Instrument

The DESI instrument, located at the Kitt Peak National Observatory (KPNO) in Arizona, collects light from the most distant parts of the universe, which enables scientists to map the cosmos as it was in its youth and track its evolution with what observed today. Understanding how the universe evolved is tied to how it ends and one of the biggest mysteries in physics: What’s behind the observation that the expansion of the universe is accelerating?

Analysis of DESI’s first year of data collection confirmed the basics of what scientists consider the best model of the universe, but also hints that there is more to learn about the underlying cause or causes of cosmic acceleration, the discovery of which led to the Nobel Prize in Physics in 2011.

Cosmic acceleration is problematic because it contradicts the way gravity, which causes objects with mass to be pulled together, is observed to operate in our solar system and in nearby space.

“Gravity pulls matter together, so when we throw a ball in the air, Earth’s gravity pulls it down toward the planet,” Ishak-Boushaki said. “But on the largest scales, the universe works differently. It’s acting like there’s something repulsive pushing the universe apart and accelerating its expansion. This is a big mystery and we are investigating it on several fronts. Is it an unknown dark energy in the universe, or is it a modification of Albert Einstein’s theory of gravity on a cosmological scale?

Exploring Dark Energy and the Expansion of the Universe

Dark energy is thought by many scientists to play a key role in cosmic acceleration, but it is not well understood. Some theorize that it’s a cosmological constant—an intrinsic property of space that drives acceleration.

To study the effects of dark energy over the past 11 billion years, the DESI group has created the largest 3D map of the cosmos ever built using the most precise measurements to date. This is the first time scientists have measured the expansion history of the young universe with an accuracy of better than 1%.

The leading model of the universe is known as Lambda-CDM. It includes both ordinary matter and a rarely interacting type of matter called cold dark matter (CDM) and dark energy, known as Lambda. Both matter and dark energy shape how the universe expands, but in opposite ways. Through gravitational pull, matter and dark matter slow down the expansion, while dark energy speeds it up. The amount of each affects how the universe evolves. This model is effective in validating results from previous experiments and describing what the universe looks like over time, Ishak-Boushaki said.

This animation shows how the baryon’s acoustic oscillations act as a cosmic ruler for measuring the expansion of the universe. Credit: Claire Lamman/DESI collaboration and Jenny Nuss/Berkeley Lab

When DESI’s first-year results are combined with data from other studies, however, there are some subtle differences from what the Lambda-CDM model would predict.

“Our results show some interesting deviations from the standard model of the universe that may indicate that dark energy is evolving over time,” said Ishak-Boushaki. “The more data we collect, the better equipped we will be to determine whether this finding holds. With more data, we can identify different explanations for the result we observe or confirm it. If it holds, such a result will shed some light on what is causing the cosmic acceleration and provide a major step forward in understanding the evolution of our universe.”

More data will also improve DESI’s other early results, which weigh in on the Hubble constant – a measure of the expansion rate of the universe today – and the mass of particles called neutrinos.

The importance of blind analysis in research

DESI is the first spectroscopic experiment to perform a completely blind analysis, which hides the true result from the scientists to avoid any subconscious confirmation bias. Researchers work “blind” with edited data and write computer code to analyze their findings. Once everything is finalized, they apply their analysis to the original data to discover the actual answer.

“Dr. Ishak-Boushaki’s research and his collaboration with scientists at nearly 70 institutions are revealing important insights about our universe, and the results are fascinating,” said Dr. David Hyndman, dean of NSM and president emeritus of the Francis S. and Maurine G. Johnson University. . “It is inspiring to have such world-class research programs at UT Dallas and to see our scientists play key roles in fundamental discoveries.”

Reference: “Year 1 Cosmology Results” by DESI Collaboration et al., 4 April 2024.

DESI was built and operated with funding from the Department of Energy’s (DOE) Office of Science and sits atop the National Science Foundation’s (NSF) Nicholas U. Mayall 4-meter telescope at KPNO, which is operated by the NSF NOIRLab. DOE’s Lawrence Berkeley National Laboratory manages the DESI experiment.

DESI is also supported by the National Energy Research Center for Scientific Computing, the primary computing facility for the DOE Office of Science. Additional support for DESI is provided by NSF; UK Science and Technology Facilities Council; Gordon and Betty Moore Foundation; Heising-Simons Foundation; French Commission of Alternative Energies and Atomic Energy; National Council of Humanities, Sciences and Technologies of Mexico; Ministry of Science and Innovation of Spain; and DESI member institutions.

The DESI Collaboration is honored to be allowed to conduct scientific research on Iolkam Du’ag (Maja Kitt), a mountain of special significance to the Tohono O’odham Nation.