Universe‘s Expansion May Be Slowing, Challenging Dark Energy Theories
New research suggests the universe is not accelerating its expansion as previously thought, potentially overturning the standard model of cosmology and raising questions about the nature of dark energy. A team of astronomers analyzing data from 300 galaxies has found evidence that distant Type Ia supernovas are dimmer than expected, indicating a transition to decelerating expansion may have already occurred.
For decades, scientists have believed the universe’s expansion is accelerating, driven by a mysterious force called dark energy. This understanding is rooted in the Lambda Cold Dark Matter (LCDM) model, the prevailing framework for cosmic evolution. However, the new study, published Wednesday (Nov. 5) in the Monthly Notices of the Royal Astronomical society, challenges this view by accounting for a previously uncorrected bias in supernova observations – the age of the host galaxies.
“By contrast, our analysis – which applies the age-bias correction – shows that the universe has already entered a decelerating phase today,” explained researcher Lucas Lee. Previous analyses,like those from the Dark Energy Spectroscopic Instrument (DESI) project,combined uncorrected supernova data with other measurements,leading to the conclusion that while the universe will decelerate in the future,it is currently still accelerating.
Type Ia supernovas, resulting from the explosion of white dwarf stars, are considered “standard candles” – objects with known intrinsic brightness. By comparing their apparent brightness to their distance, astronomers can measure the expansion rate of the universe. The team’s findings suggest that the dimming of these distant supernovas isn’t solely due to the expansion of space, but also influenced by stellar effects within their host galaxies.
The research team plans to further validate these results with an “evolution-free test” using young Type Ia supernovas from young galaxies at varying distances. The Vera C. Rubin Observatory, recently operational in Chile with the world’s largest digital camera, is expected to provide crucial data for this investigation, potentially discovering over 20,000 new supernova host galaxies within the next five years.
“Within the next five years, with the Vera C. rubin Observatory discovering more than 20,000 new supernova host galaxies, precise age measurements will allow for a far more robust and definitive test of supernova cosmology,” said team member Chul Chung, a researcher at Yonsei University. If confirmed, these findings would necessitate a re-evaluation of our understanding of dark energy and the fundamental forces governing the universe.
