The expansion of the universe is still accelerating under the influence of dark energy, despite recent claims to the contrary, according to new research. This means that dark energy, the mysterious force that dominates the universe, is not weakening but continues to get stronger, considered something of a "cosmological crisis" as it was so against expectations.

In 1998, via the study of cosmic explosions called Type Ia supernovas, astronomers discovered that not only is the universe expanding, but that the speed of that expansion is increasing. "Dark energy" was the name given to the mysterious force driving this accelerating expansion. Since then, scientists have discovered that dark energy accounts for around 70% of the universe's matter and energy.

In November 2025, research was published that suggested the expansion of the universe was slowing, meaning dark energy would be weakening. But this new research suggests that these findings from last year might not be a cosmic hand grenade thrown into the cosmological apple cart, but instead may have actually emerged from a scientific misunderstanding.

"Thankfully, we have averted this crisis, but the mystery about why the rate of expansion of the universe is still accelerating remains," lead author of the new refuting research, Phil Wiseman, from the University of Southampton in the UK, said in a statement. "The previous and well-accepted measurements were, in fact, fine, and our current understanding of the fate of the universe remains robust. 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."

The research from 2025 that suggested dark energy was weakening was based upon a reassessment of the brightness of Type Ia supernovas, which occur when a dead star called a white dwarf overfeeds on a companion star. This causes a runaway nuclear explosion of such uniform brightness that it can be used to measure cosmic distances. In fact, these explosions are so uniform that astronomers refer to them as "standard candles."

This prior research determined, incorrectly it now seems, that as the universe has aged, the brightness of Type Ia supernovas had changed, leading to incorrect measurements of distances based on them as well as incorrect estimates of the speed of the universe's expansion. Both of these led to the suggestion that dark energy is weakening.

But Wiseman and colleagues found this previous team had made an error in how they calculated the ages of exploding white dwarfs, finding they had assumed the ages of these stars would be the same as the ages of the galaxies in which they exploded.

They also found the 2025 research hadn't accounted for a common correction used in cosmology that factors in the masses of galaxies in which Type Ia supernovas occur.

"Extraordinary claims require especially careful testing," team member Adam Riess, who in 2011 shared the Nobel Prize for the discovery of dark energy, 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."

While the challenge to dark energy's growing dominance over the universe seems now to have been refuted, the back and forth on this topic shows how ideas in science aren't dogma and remain open for revision.

"This is how progress is made," team member Mark Sullivan, also from the University of Southampton, said. "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."

The team's research was published on June 10 in the journal Monthly Notices of the Royal Astronomical Society.

One of the most hotly debated mysteries in astronomy is set to continue, as new research fails to rule out self-annihilating dark matter as the source of gamma-ray emissions from the heart of the Milky Way. Known as the Galactic Center Excess, a spherical gamma-ray glow extending out for thousands of light-years from the core of our galaxy, this high-energy light has baffled researchers for over a decade.

While several possible explanations for the Galactic Center Excess have been put forward, including a population of rapidly spinning neutron stars called pulsars, one of the most prevalent has been a specific type of dark matter particle. Dark matter is the mysterious stuff that accounts for 85% of the universe's matter. It is effectively invisible because it doesn't interact with light or with "ordinary" matter composed of atoms. That fact has led to many possible dark matter candidate particles being proposed, including some that self-annihilate. This is akin to what happens when an electron meets its antimatter counterpart, or positron. The two annihilate each other, releasing energy into the cosmos.

For self-annihilating dark matter, these particles would be their own antiparticles, meaning when they interact, they would annihilate and release energy as gamma rays. With dark matter outweighing ordinary matter by a ratio of five to one, one might expect this annihilation to be occurring constantly, flooding the cosmos with gamma rays, but dark matter rarely interacts with itself in this model. Thus, dark matter annihilation is only a factor when this mysterious stuff is densely clustered in a region like the heart of a galaxy.

Unfortunately, investigating the heart of the Milky Way is challenging indeed.

"Interpreting the signal is particularly difficult because the Galactic Center is an exceptionally bright and crowded region of the gamma-ray sky," team member and University of Vienna researcher Florian List said in a statement.

Getting to the point

To investigate if annihilating dark matter could indeed account for the Galactic Center Excess, List and colleagues turned to machine learning trained on more than a million simulated gamma-ray observations. Previous similar approaches had pointed to comparatively bright, unresolved light sources as a potential source of the Galactic Center Excess. However, this new research showed that these point sources, including pulsars, would be extremely faint, and that is good news for scientists who favor annihilating dark matter as the cause of these gamma rays.

That is because, whereas previous research has suggested just a few hundred pulsars could be enough to account for the Galactic Center Excess, these findings indicate that the pulsar population at the heart of the Milky Way would have to be greater than 35,000.

"Our new analysis shows that the sources would have to be so faint that they would be almost indistinguishable from the emission expected from annihilating dark matter," team member Nick Rodd, a scientist at the Lawrence Berkeley National Laboratory, said.

While this research may keep dark matter in the game as a plausible explanation, it far from confirms the annihilation of this mysterious stuff as the source of the Galactic Center Excess. "The origin of the Galactic Center Excess is one of the longest-running debates in astrophysics," List said. "Our work does not show that dark matter is responsible for the signal. However, it suggests that it is still too early to rule out this possibility."

The team's research was published on Thursday (Feb. 5) in the journal Physical Review Letters.