Dark energy, the mysterious force driving the universe’s expansion, may not be the constant we once thought. New data from the Dark Energy Spectroscopic Instrument (DESI) suggests this enigmatic entity could be evolving, potentially reshaping our understanding of the cosmos and its ultimate fate.
DESI, a collaborative project involving over 900 researchers, has been mapping the universe, creating immense sky maps and revealing colossal cosmic structures. This latest data release challenges the prevailing model of the universe, known as Lambda-CDM, which assumes dark energy is a cosmological constant, unchanging over time.
The universe’s composition is a fascinating puzzle. Ordinary matter, everything we can see and touch, accounts for a mere 5%. Dark matter, detectable only through its gravitational influence, comprises about 27%. The remaining 68% is attributed to dark energy, the force seemingly responsible for the accelerating expansion of the universe.
The Lambda-CDM model hinges on the idea of dark energy as a constant, behaving the same way billions of years ago as it does today. However, DESI’s findings suggest otherwise. “Results from the first batch of data hinted at this possibility, but the evidence wasn’t conclusive,” explains Rossana Ruggeri, a physicist at the University of Queensland involved in the DESI analysis. “The second batch of data strengthens this evidence.”
While the new data doesn’t yet meet the rigorous statistical threshold for a definitive discovery, it bolsters the suspicion that dark energy may be dynamic. This could have profound implications. “If dark energy is changing, it could dramatically alter the universe’s ultimate fate,” Ruggeri notes. The universe might continue its accelerating expansion or, conversely, collapse inward in a “Big Crunch.”
Presented at the American Physical Society’s Global Physics Summit, these findings are detailed in several preprints on arXiv. The first data release, a massive 270 terabytes, represents just a fraction of the information DESI will gather over its five-year survey. It already contains data on 18.7 million deep-space objects, including distances to remote galaxies spanning 11 billion years of cosmic history. This data is publicly accessible, and some can be explored through the Legacy Survey Sky Browser.
“DESI consistently produces 3D universe maps ten times larger each decade,” says David Schlegel, a lead scientist at Berkeley Lab for DESI. “This rapid progress is fueled by advancements in instrument design, technology, and the analysis of increasingly faint galaxies.”
Positioned on the Nicholas U. Mayall 4-meter telescope in Arizona, DESI can collect data on over 100,000 objects nightly under optimal conditions. This first release contains more than double the unique extragalactic objects of all previous 3D spectroscopic surveys combined, highlighting the scale of information being gathered.
Currently in its fourth year, DESI aims to record spectra for over 50 million galaxies and quasars before its survey concludes. Extensive data processing and analysis will follow. This work may ultimately lead to a revised understanding of dark energy and its evolving role in the universe’s grand narrative.
