Our understanding of the universe remains solid, say astronomers whose new study has found the expansion of the universe is still accelerating as previously found.
In late 2025, a team of astronomers shocked the space community with claims that the evidence of dark energy – a mysterious force that pushes the cosmos apart – was weakening such that the expansion is no longer accelerating.
They suggested the methods used to measure the universe’s expansion using supernovae, or exploding stars, were fundamentally flawed.
But a new study led by the University of Southampton, which re-evaluated the data, has found that the universe is behaving exactly as expected.
Experts behind the paper, published in the Monthly Notices of the Royal Astronomical Society, include renowned Nobel Prize-winning astrophysicists Professor Adam Riess and Professor Brian Schmidt.
Lead author Dr Phil Wiseman, from the University of Southampton, said the debate that followed last year’s revelations was the result of a scientific misunderstanding rather than a flaw in the universe itself.
He added: “The previous and well accepted measurements were, in fact, fine and our current understanding of the fate of the universe remains robust.
“Thankfully we have averted this crisis, but the mystery about why the universe is still accelerating in size remains.
“By proving our measurements are correct, we can get back to trying to understand what dark energy actually is, rather than wondering if it exists at all.”
The original discovery of the accelerating expansion of the universe, made by Profs Riess and Schmidt with American astrophysicist Saul Perlmutter, won the Nobel Prize in Physics in 2011.
If the 2025 claims had been true, it would have dismantled their findings as well as nearly three decades of astronomical progress.
Professor Adam Riess said: “Extraordinary claims require especially careful testing.
“What we find is that when we calibrate these supernovae, accounting for different host environments and populations, the evidence for cosmic acceleration remains remarkably consistent.”
To measure the universe, the Southampton-led team looked closely at Type Ia supernovae – violent, luminous white dwarf star explosions – to calculate vast cosmic distances.
The 2025 study had claimed that, as the universe aged, these supernovae had different maximum brightnesses, tricking astronomers into thinking the cosmos was accelerating when it was slowing.
However, the new Southampton study found the error lay in how the age of these stars was estimated.
They proved that the previous findings incorrectly assumed the age of a galaxy was the same as the age of the star that exploded.
The experts also said the 2025 paper failed to account for the mass of host galaxies, a standard correction used in modern cosmology to prove accuracy.
Professor Mark Sullivan, also from the University of Southampton, said that challenging accepted theories and observations is fundamental to science.
He added: “This is how progress is made. Although this idea did not turn out correct, it has opened up new ways of thinking about how supernovae explode and how we can measure dark energy more accurately.”
Paper co-author Dr Brodie Popovic added: “We’ve recently been really focused on astrophysics of the explosions and how they impact cosmology.
“This was a good opportunity to go back and go over all of our assumptions – it turns out, yes, we do understand this stuff and we’re accounting for it in our cosmology measurement.”
IMAGE CREDIT: Credit NASA, JPL-Caltech, S Stolovy (SSC/Caltech)..
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