New analysis reaffirms universe's

An international team of astrophysicists, including two Nobel Laureates, has concluded the universe is still expanding at an accelerating rate. Their new analysis, published in Monthly Notices of the Royal Astronomical Society on August 29, 2026, directly refutes a South Korean study from last November which suggested cosmic expansion might be slowing.

The researchers, led by Dr. Phil Wiseman from the University of Southampton, argue the earlier claim resulted from a misunderstanding in data analysis. According to the team, the standard cosmological picture remains intact: a mysterious force called dark energy continues to drive the acceleration. "Thankfully we have averted this crisis, but the mystery about why the rate of expansion of the universe is still accelerating remains," said Dr. Wiseman in a statement provided by the Royal Astronomical Society.

Supernovae and the acceleration debate

The debate centers on observations of Type Ia supernovae. These extremely bright stellar explosions were used by Professors Adam Riess and Brian Schmidt, who shared the 2011 Nobel Prize in Physics, to first discover cosmic acceleration. Their method relies on the assumption that these supernovae have a consistent peak brightness, allowing them to be used as "standard candles" to measure cosmic distances.

The challenged South Korean study argued that Type Ia supernovae did not all reach the same peak brightness as the universe aged. If true, this would mean astronomers have been misreading the data, potentially mistaking a decelerating expansion for an accelerating one.

Flaws in the slowdown claim identified

The new paper identifies specific problems with the earlier analysis. The Southampton-led team says the previous study incorrectly treated the age of a galaxy as being the same as the age of the individual star that later exploded. The researchers also state the South Korean analysis did not properly account for the mass of the galaxies hosting the supernovae, a standard calibration step in modern cosmology.

Professor Adam Riess emphasized the need for rigorous testing. "Extraordinary claims require especially careful testing," he said. "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."

The enduring dark energy puzzle

While the new work defends the established model, it does not solve the fundamental mystery. The nature of dark energy, the anti-gravity-like force causing the acceleration, remains unknown. Co-author Professor Mark Sullivan noted that questioning established ideas is essential for scientific progress. "Although this idea did not turn out to be correct, it has opened up new ways of thinking about how supernovae explode and how we can measure dark energy more accurately," he said.

Fellow co-author Dr. Brodie Popovic said the controversy provided a valuable opportunity to re-examine foundational assumptions. "We've recently been really focused on astrophysics of the explosions and how they impact cosmology," Dr. Popovic said. The team's re-analysis confirmed their methods are sound, allowing them to return to the core question of what dark energy actually is.