Astronomers Confirm Dark Energy After Shock Challenge Rocked Cosmology

A major challenge to dark energy, the mysterious force believed to be driving the universe’s accelerating expansion, has been overturned by a new study.

Astronomers say a new analysis has reinforced one of the most important discoveries in modern cosmology, finding that the universe is still expanding at an accelerating rate.

The result counters a controversial claim made in late 2025 that suggested dark energy, the mysterious phenomenon thought to drive the universe’s accelerating expansion, might be weakening. If true, that claim would have called into question decades of research and a cornerstone of modern astronomy.

Instead, researchers led by the University of Southampton found that the original measurements remain reliable and that the universe appears to be behaving exactly as current models predict.

The findings were published in the Monthly Notices of the Royal Astronomical Society. The international team included Nobel Prize-winning astrophysicists Professor Adam Riess and Professor Brian Schmidt.

New Analysis Supports Dark Energy

According to lead author Dr. Phil Wiseman of the University of Southampton, the controversy that emerged after last year’s claims stemmed from a misunderstanding in the data analysis rather than a problem with the universe itself.

He said: “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 accelerating expansion of the universe was first discovered by Professors Riess and Schmidt along with American astrophysicist Saul Perlmutter. Their work earned the Nobel Prize in Physics in 2011.

Had the 2025 challenge been correct, it would have undermined not only that Nobel-winning discovery but also nearly 30 years of cosmological research built upon it.

Professor 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.”

Supernova Measurements Reexamined

To investigate the claims, the Southampton team revisited observations of Type Ia supernovae, extremely bright explosions of white dwarf stars that astronomers use to measure enormous distances across the universe.

The 2025 study argued that these supernovae reached different peak brightness levels as the universe aged. According to that interpretation, astronomers may have mistakenly concluded that cosmic expansion was accelerating when it was actually slowing down.

However, the new study identified problems with that analysis.

Researchers found that the earlier work incorrectly treated the age of a galaxy as equivalent to the age of the star that eventually exploded as a supernova. The team concluded that this assumption led to inaccurate results.

The researchers also noted that the 2025 paper did not properly account for the mass of the galaxies hosting the supernovae. This correction is routinely included in modern cosmological studies because it helps improve the accuracy of measurements.

Lessons for Cosmology

Professor Mark Sullivan of the University of Southampton emphasized that questioning established ideas remains an essential part of the scientific process.

He said: “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.”

Co-author Dr. Brodie Popovic said the study provided an opportunity to reexamine assumptions that underpin modern cosmology.

He 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.”

Reference: “Still accelerating: type Ia supernova cosmology is robust to host galaxy age evolution” by Phil Wiseman, Brodie Popovic, Mark Sullivan, Adam G Riess, Dan Scolnic, Rebecca C Chen, Tamara M Davis, Lluís Galbany, Isobel M Hook, Saurabh W Jha, Lisa Kelsey, Yukei S Murakami, Mickaël Rigault, Benjamin M Rose, Brian Schmidt, Mat Smith and Maria Vincenzi, 10 June 2026, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stag797

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