Researchers have utilized the Dark Energy Spectroscopic Instrument (DESI) to examine how close to 6 million galaxies are grouped over an incredible span of 11 billion years in cosmic history. Their findings are consistent with the predictions made by Einstein’s general relativity.
Gravity has played a pivotal role in shaping the universe. It caused minor variations in matter during the early stages of the universe to evolve into the vast networks of galaxies observable today. A recent study leveraging data from the Dark Energy Spectroscopic Instrument (DESI) has meticulously traced the development of this cosmic structure, marking the most accurate assessment of gravity at vast distances to date.
DESI is a global collaborative effort involving over 900 scientists from more than 70 institutions worldwide and is overseen by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). In this latest research, DESI scientists confirmed that gravity operates in accordance with Einstein’s theory of general relativity. This finding supports our current understanding of the universe and restricts alternative theories of modified gravity which have been suggested to account for unexpected phenomena, such as the accelerating expansion of the universe often attributed to dark energy.
“General relativity has been thoroughly examined within the confines of solar systems; however, we needed to ensure this principle holds true on a much larger scale,” remarked Pauline Zarrouk, a cosmologist at the French National Center for Scientific Research (CNRS) at the Laboratory of Nuclear and High-Energy Physics (LPNHE), who co-led this new analysis. “By investigating how galaxies formed over time, we can directly scrutinize our theories, and so far, our findings align with the predictions of general relativity on cosmic scales.”
The research also established new upper boundaries on the mass of neutrinos, the only fundamental particles whose masses remain imprecisely determined. Previous experiments indicated that the combined masses of the three neutrino types must be at least 0.059 eV/c2 (for reference, an electron has a mass of roughly 511,000 eV/c2). The results from DESI suggest that the total must be under 0.071 eV/c2, which leaves a limited range for the masses of neutrinos.
Today, the DESI collaboration released their findings in several papers uploaded to the arXiv online repository. The intricate analysis examined nearly 6 million galaxies and quasars, allowing researchers to look back 11 billion years. In just a single year of data, DESI has achieved the most accurate overall measurement of structural growth, outpacing previous endeavors that spanned decades.
The results announced today extend the analysis of DESI’s data from its first year, which in April unveiled the largest three-dimensional map of the universe thus far and hinted at a potential evolution in dark energy over time. The initial findings focused on a specific aspect of galaxy clustering known as baryon acoustic oscillations (BAO). The newly released analysis, termed a “full-shape analysis,” broadens the investigation to draw more insights from the data, evaluating how galaxies and matter are distributed across various scales in space. This study involved months of further work and validations, utilizing a technique to conceal the results from the scientists until the study’s conclusion to minimize any unconscious bias.
“Both our BAO results and the full-shape analysis are exceptional,” said Dragan Huterer, a professor at the University of Michigan and co-lead of DESI’s team interpreting the cosmological data. “This marks DEI’s inaugural exploration into the growth of cosmic structure. We’re unveiling an extraordinary capability to examine modified gravity and tighten the constraints on dark energy models. And this is merely the beginning.”
DESI is an advanced tool that can simultaneously capture light from 5,000 galaxies. It was built and is operated with funding from the DOE Office of Science. DESI is situated on the Nicholas U. Mayall 4-meter Telescope at the Kitt Peak National Observatory (part of NSF NOIRLab). The project is currently in its fourth year of a five-year sky survey, aiming to gather roughly 40 million galaxies and quasars by the project’s conclusion.
The collaboration is presently analyzing the data collected during the first three years and plans to present updated findings on dark energy and the universe’s expansion history in spring 2025. The expanded results released today align with the prior inclination towards an evolving dark energy, increasing excitement for the forthcoming analysis.
“Dark matter accounts for roughly a quarter of the universe, while dark energy comprises another 70 percent, yet we still have little understanding of either,” stated Mark Maus, a PhD student at Berkeley Lab and UC Berkeley, involved in theorizing and validating modeling processes for the new analysis. “The prospect of capturing images of the universe and addressing these monumental, fundamental questions is truly astounding.”
Support for DESI comes from the DOE Office of Science and the National Energy Research Scientific Computing Center, a facility operated by the DOE Office of Science. Additional backing is provided by the U.S. National Science Foundation, the Science and Technology Facilities Council in the U.K., the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, the French Alternative Energies and Atomic Energy Commission (CEA), the National Council of Humanities, Sciences, and Technologies of Mexico, the Ministry of Science and Innovation of Spain, as well as other member institutions of DESI.
The DESI collaboration is privileged to be allowed to conduct scientific investigations on I’oligam Du’ag (Kitt Peak), a site of significant cultural importance to the Tohono O’odham Nation.
Several related papers: https://data.desi.lbl.gov/doc/papers/
