No crisis? Universe’s expansion is accelerating, study says

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Space No crisis? Universe’s expansion is accelerating, study says

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June 18, 2026

This is RCW 86, the remnant of a Type 1a supernova 8,000 light-years away. Studying Type 1a supernovae led to the discovery that the universe’s expansion is accelerating. An astonishing 2025 study called this discovery into question. But now, new research claims to have found flaws in the 2025 paper. Image via NASA/ CXC/ SAO/ ESA (X-ray)/ JPL-Caltech/ B. Williams (infrared).<br>The Royal Astronomical Society originally published this article on June 11, 2026. Edits by EarthSky.

No crisis? Universe’s expansion is accelerating after all, study says

Our universe’s expansion is still accelerating despite recent claims suggesting otherwise, an international team of astrophysicists say.

They have refuted a study published last year claiming the growth of the universe is slowing. Instead, the researchers insist there is no flaw in the widely-accepted theory that a mysterious force known as dark energy is driving the expanding cosmos.

The researchers include two Nobel laureates and represent institutions worldwide. They say the debate that followed last November’s revelations was the result of a scientific misunderstanding, rather than a cosmic grenade threatening to blow apart everything we know about the universe.

They published their rebuttal on June 10, 2026, in the peer-reviewed journal Monthly Notices of the Royal Astronomical Society.

Rebutting an extraordinary paper

The new research is a direct rebuttal of a study by a team of South Korean researchers published in November 2025. Their paper made the claim that the universe’s expansion might in fact be slowing down. This would be due to the influence of dark energy – which acts as a kind of anti-gravity – weakening over time.

Lead author Phil Wiseman, from the University of Southampton, 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 rate of expansion of the universe is still accelerating remains.

By proving our measurements are correct, we can get back to trying to understand what this dark energy actually is, rather than wondering if it exists at all.

What were the flaws?

The international team of researchers involved in the new study included Adam Riess and Brian Schmidt, who collectively won the 2011 Nobel Prize in Physics alongside Saul Perlmutter.

The trio studied Type Ia supernovae, violent, luminous white dwarf star explosions and determined that more distant objects appeared to move faster. This lead to their conclusion that the universe’s expansion was accelerating.

This has been the globally-accepted theory ever since, although last year’s research by the South Korean team threatened to upset the applecart. It claimed that, as the universe aged, these supernovae had different maximum brightnesses. This tricked astronomers into thinking the cosmos was accelerating when it was in fact slowing.

But the University of Southampton-led researchers found an error in how the age of these stars was estimated. They say 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 South Korean paper failed to account for the mass of host galaxies. That is a standard correction used in modern cosmology to prove accuracy.

Riess added:

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.

Science is never settled

Mark Sullivan, also from the University of Southampton, said challenging accepted theories and observations was fundamental to science.

This is how progress is made. 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.

Fellow co-author Brodie Popovic agreed:

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.

Bottom line: Rebutting a surprising paper from 2025, a...