A team of scientists, including University of Hawaiʻi researchers, has found further observational support for a model originally developed at UH Mānoa that could help solve two of the biggest mysteries in physics: the accelerating growth of the universe and the mass of ghost-like particles called neutrinos.
In a study published in Physical Review Letters on August 21, the researchers used data from the Dark Energy Spectroscopic Instrument (DESI) to test whether dark energy emanating from black holes could be responsible for the mysterious force causing the universe to expand faster throughout time. DESI, located at the Kitt Peak National Observatory on land stewarded by the Tohono O’odham Nation in Arizona, uses 5,000 robotic eyes to map millions of galaxies, helping scientists measure how quickly the universe has grown over billions of years.
This idea, called the cosmologically coupled black hole (CCBH) hypothesis, is based on black holes that convert dead star matter into dark energy. Such dark energy black holes have been studied for over half a century, but their relation to the universe’s growth was not initially appreciated. Duncan Farrah, UH Mānoa associate professor in the Department of Physics and Astronomy and graduate faculty at the Institute for Astronomy; Kevin Croker, affiliate graduate faculty in the UH Mānoa Department of Physics and Astronomy; and Joel Weiner, professor emeritus in the UH Mānoa Department of Mathematics, were the first to explore how such a population of black holes could give rise to the accelerated growth that scientists observe today.
“The upshot of this is that if you convert just a little bit of ordinary matter into dark energy over the history of the universe, then you can go a significant way to solving two big mysteries. You explain the origin of dark energy, and you solve a significant tension in the world of particle physics,” Farrah said. “This doesn’t prove anything, but it does motivate further examination of the idea, and testing it against other possible explanations.”
One of the most puzzling findings from DESI is that the standard explanation for accelerated growth of the universe seemed to leave no room for a type of particle called a neutrino to have mass. DESI used the expansion of the universe itself as a giant set of scales, but found that, in the standard model of cosmology, measured mass of neutrinos had begun to contradict measurements from other experiments.
The CCBH model offers a solution. If black holes are turning star matter into dark energy, then the total amount of non-neutrino matter in the universe would decrease over time. This correction allows the neutrino mass measured in DESI data to match what Earth-based experiments have found, something only one other model has done successfully. And it can do so while also explaining the observed accelerated growth of the universe as a whole.
The research explains the amount of dark energy in the universe, suggesting that it wasn’t set at the beginning of time but built up slowly as stars formed and died. The work shows how creative thinking, combined with powerful telescopes and global cooperation, can bring us all closer to understanding how the universe really works.
More about DESI
DESI is an international experiment that brings together more than 900 researchers from more than 70 institutions. The project is led by Lawrence Berkeley National Laboratory, and the instrument was constructed and is operated with funding from the U.S. Department of Energy (DOE) Office of Science. DESI is mounted on the U.S. National Science Foundation’s (NSF) Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory—a program of NSF NOIRLab—in Arizona.
In addition to its primary support from the DOE Office of Science, DESI is also supported by the National Energy Research Scientific Computing Center, a DOE Office of Science user facility. Additional support for DESI is provided by the NSF; the Science and Technology Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies 2 and Atomic Energy Commission; the National Council of Humanities, Sciences, and Technologies of Mexico; the Ministry of Science and Innovation of Spain; and by the DESI member institutions.