A comprehensive new analysis of Type Ia supernovae refutes the controversial claim from 2025 suggesting that the expansion of the universe is slowing down.
Type Ia supernovae serve as a fundamental aspect of modern cosmology, providing initial evidence for cosmic acceleration as well as opportunities for new dark energy experiments. Image credit: Alex Parker / NASA / SDSS.
In 2025, a study led by Yong-wook Lee from Yonsei University surprised the scientific community by claiming that indications of dark energy had diminished, asserting that the universe’s expansion was no longer accelerating.
The researchers proposed that the methodologies employed in measuring cosmic expansion via supernovae were inherently flawed.
Dr. Phil Wiseman of the University of Southampton, lead author of the latest study, noted, “The debate following last year’s claims stemmed from a scientific misinterpretation rather than an actual flaw in the universe’s behavior.”
He affirmed, “Earlier measurements, which have long been accepted, remain valid, and our current understanding of the universe’s future is intact.”
“Fortunately, we have sidestepped a crisis, but the question of why the universe is still expanding at an accelerated rate persists.”
“By validating our measurements, we can redirect our focus toward unraveling the true nature of dark energy, rather than questioning its existence,” he added.
The initial discovery of the universe’s accelerated expansion received the Nobel Prize in Physics in 2011.
If the assertions made in 2025 were valid, they would reverse nearly three decades of astronomical progress.
Nobel laureate Professor Adam Rees, a co-author of the new investigation, remarked, “Extraordinary claims necessitate thorough scrutiny.”
“Our findings reveal that once we adjust for varying host environments and populations of supernovae, the evidence for cosmic acceleration remains impressively consistent.”
To assess cosmic distances, the authors meticulously analyzed Type Ia supernovae.
The 2025 study posited that as the universe ages, these supernovae exhibit varying peak brightness levels, misleading astronomers into believing that the universe is decelerating.
Contrary to this, the new research indicates that the methodology employed to ascertain the ages of these celestial bodies was flawed.
Researchers demonstrated that previous work incorrectly assumed that the age of the galaxy matched the age of the exploded star.
They further pointed out that the 2025 publication neglected the mass of the host galaxy, a critical correction typically made to ensure precision in contemporary cosmological studies.
Co-author Professor Mark Sullivan of the University of Southampton stated, “Challenging established theories is crucial in the scientific process.”
“While this idea proved incorrect, it has inspired new discussions regarding supernova explosions and the more accurate measurement of dark energy.”
“We have recently intensified our focus on the astrophysics of supernova explosions and their implications for cosmology,” remarked study co-author Dr. Brody Popovich, an astronomer at the University of Southampton.
“This was an excellent chance to reevaluate our underlying assumptions. It turns out that we have indeed understood this and incorporated it into our cosmological assessments.”
Upcoming research will be published in Royal Astronomical Society Monthly Notices.
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Phil Wiseman et al. 2026. Still accelerating: Type Ia supernova cosmology remains robust against galactic age evolution. MNRAS 549 (3): stag797; doi: 10.1093/mnras/stag797
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Source: www.sci.news
