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Recent research from the DESI community confirms the Standard Model of gravity and hints at the development of dark energy based on detailed analysis of data from millions of galaxies and quasars. These results contribute significantly to the understanding of the accelerated expansion of the universe. A physicist from the University of Texas at Dallas, along with an international team of researchers in the Dark Energy Spectroscopic Instrument (DESI) collaboration, is conducting a multi-year mission to solve one of the biggest mysteries in astrophysics: why is the expansion of the universe accelerating?
Scientists have proposed competing theories to explain this phenomenon. One theory suggests that dark energy, an unknown force, is tearing galaxies apart. Another theory posits that gravity—the force that binds objects in local systems like our solar system—behaves differently on large cosmic scales and may need to be revised to account for accelerated expansion.
Testing the theories of gravity and expansion
The DESI collaboration, which involves more than 900 scientists from more than 70 institutions, has published a new analysis addressing the second theory. Their findings show that the galaxy cluster is consistent with the standard model of gravity: Albert Einstein's general theory of relativity, which also explains how objects fall under the influence of gravity and how planets orbit stars. The analysis provides the most accurate test to date of how gravity behaves on very large scales, tracking how the cosmic structure has grown over the past 11 billion years.
Groundbreaking discoveries in cosmological research
The scientists involved in the collaboration shared their findings in several papers published Nov. 19 in arXiv, an online repository of peer-reviewed scientific articles. Dr. Mustafa Ishak-Boushaki, professor of physics at the University of Dallas' School of Life Sciences and Mathematics, co-led the DESI task force that interpreted the cosmological data, and is lead author of the paper, which presents a detailed analysis of the cosmic-scale gravity test.
“For this round of DESI results, I focused my efforts at UT Dallas on much of the analysis of gravity, which places constraints on how matter in the universe moves and how large-scale structures such as galaxy clusters evolve. ", said Ishak-Bushaki, an astrophysicist whose research career has focused on questions of cosmology. "The DESI results, combined with data sets from other experiments, are consistent with general relativity at work on cosmic scales, although they do not completely rule out other theories of modified gravity."
Reaching Dark Energy and Cosmic Structures
Ishak-Bushaki plans to present the cosmology results with other researchers on behalf of the DESI collaboration in January at a meeting of the American Astronomical Society in National Harbor, Maryland. The new results provide an expanded analysis of the first year of DESI data, which in April helped create the largest 3D map of the universe to date and revealed hints that dark energy may evolve over time.
"The latest analysis is also consistent with our previous findings, which favor the theory that dark energy is dynamic rather than constant, which is a very important result for cosmic acceleration," Ishak-Bushaki said.
The DESI experiment can capture light from 5000 galaxies simultaneously. The latest analysis used data from nearly 6 million galaxies and quasars, allowing researchers to see up to 11 billion years into the past. With only one year of data, DESI has made the most accurate overall measurement of structure growth in the universe, surpassing previous efforts that took decades.
The latest analysis also provided new upper limits on the mass of neutrinos, the only fundamental particles whose masses have not yet been precisely measured. The new analysis expands the possibilities for extracting more information from the data, measuring how galaxies and matter are distributed at different scales in space. As in the previous study, it used a technique to hide the result from the scientists until the end, mitigating any unconscious bias.
The DESI experiment is now in its fourth of five years of studying the sky, and researchers plan to collect data from about 40 million galaxies and quasars by the time the project ends. The collaboration is currently analyzing the first three years of data collected and expects to present updated measurements of dark energy and the history of the universe's expansion in March at a meeting of the American Physical Society.
The Dark Energy Spectroscopic Instrument (DESI) was established and operates with financial support from the Department of Energy's (DOE) Office of Science. It is mounted on the Nicholas W. Mayall 4-meter telescope at Kitt Peak National Observatory, operated by the National Science Foundation's (NSF) NOIRLab. The DESI experiment is overseen by the US Department of Defense's Lawrence Berkeley National Laboratory.
DESI receives additional support from the National Energy Research Computing Center, DOE's Office of Science. Funding also comes from the National Science Foundation, the Council of Science and Technology Institutions of Great Britain, the Gordon and Betty Moore Foundation, the Huizing-Simons Foundation, the Commission on Alternative Energy and Atomic Energy of France, the National Council of Humanities, Sciences, and Technologies of Mexico, the Ministry of of Science and Innovation of Spain and DESI member institutions.
The DESI collaboration recognizes and respects the privilege of conducting research at I'oligam Du'ag (Kitt Peak), a site of deep cultural and spiritual significance to the Tohono O'odham Nation.
