Astronomers have combined nearly 2,900 exploding stars into the largest standardized supernova dataset yet assembled, and the result deepens a problem for the model that has anchored cosmology for a generation. Rather than confirming that dark energy behaves as a fixed, unchanging force, the new analysis adds to a small but growing body of evidence that its strength may shift over cosmic time. The work comes from a team at the University of Queensland working with international collaborators, and it arrives alongside an independent result built on a completely different method, which is what has researchers paying closer attention.
Rebuilding Three Decades of Supernova Data Into One Framework
The project unified 2,884 Type Ia supernovae, the standard candles astronomers use to measure cosmic distances because they explode with a predictable peak brightness. “Our project sets a new global benchmark in supernova cosmology and provides the clearest picture yet of how the universe has expanded over time,” said University of Queensland Ph.D. candidate Ryan Camilleri. “We’ve rebuilt three decades of astronomical observations into a single, consistent framework.” Camilleri and colleagues went back through older observations and applied newer knowledge of how supernovae actually behave, correcting for cosmic dust along the line of sight and the mass of a supernova’s host galaxy, both of which can distort the light reaching Earth. They also accounted for gravitational lensing, the bending and magnification of light as it passes near massive objects on its way from a distant supernova to a telescope.
A Compilation Built on Pantheon+ and the Dark Energy Survey
The new catalog, described in a paper titled “Supernovae Unite: Combining Pantheon+ and DES-SN5YR,” folds historic supernova measurements together with data the Dark Energy Survey (DES) published in 2024. Combining datasets collected by different telescopes with different instruments over multiple decades required linking their calibration so that a supernova photographed in the 1990s could be compared fairly with one photographed last year. Then the team layered in cosmic microwave background measurements, the relic light left over from the Big Bang, along with maps showing how galaxies are distributed through space, to sharpen the constraints on how dark energy has behaved.
Two Independent Techniques, One Overlapping Signal
What makes the result notable is that it is not standing alone. “Our supernova data from DES in 2024 first showed hints that dark energy may be time varying, and this new compilation also sees a deviation from the standard model although in a slightly different direction,” said University of Queensland’s Professor Tamara Davis. “Similarly, results from the Dark Energy Spectroscopic Instrument (DESI) found hints of variations in dark energy in its surveys of relic sound waves from the early universe. So, two completely independent measurements have found hints of time variation in dark energy, challenging the standard model that dark energy doesn’t change.” DESI measures dark energy through baryon acoustic oscillations, faint patterns in how galaxies cluster that trace sound waves that rippled through the early universe, an entirely different technique from tracking supernova brightness across cosmic distances.
Why the Cosmological Constant Has Been the Default Assumption
The prevailing framework, known as Lambda-CDM, treats dark energy as a constant that makes up roughly 70 percent of the universe’s total energy content and counteracts the gravitational pull of cold dark matter. That assumption traces back to the 1998 discovery of the universe’s accelerating expansion, work that earned a Nobel Prize and was itself built on standardized Type Ia supernova measurements. A separate standardized compilation called Union3, assembled by the Supernova Cosmology Project at Lawrence Berkeley National Laboratory, reported similar hints of evolving dark energy in 2025 after combining 2,087 supernovae spanning roughly seven billion years of cosmic history. Saul Perlmutter, who shared the 2011 Nobel Prize for the original discovery of dark energy and co-authored the Union3 study, described the field’s mood as cautious rather than celebratory: researchers are increasingly reaching levels of precision where the different theoretical models of dark energy can finally be told apart, but the pattern could still weaken as more data arrives.
What a Weakening Dark Energy Would Mean for the Universe’s Fate
If dark energy is genuinely losing strength rather than holding constant, the implications extend well past bookkeeping in a cosmological model. Whether the universe expands forever, slows to a stall, or eventually reverses into contraction depends on the balance between dark energy and matter. Camilleri suggested the stakes go further still: “All of this research may also hold the clue to explain how gravity and quantum physics fit together. We know these two theories are each immensely successful in their own realms, so if we can figure out how to put them together that would be a huge step in theoretical physics.”
Next-Generation Surveys Will Decide If the Signal Holds
Neither team is calling the case closed. The deviation from a constant dark energy remains a statistical hint rather than a firm detection, and the Union3 team has cautioned that the pattern could weaken once more data arrives. Much larger supernova samples are already on the way: the Vera C. Rubin Observatory, which recently released its first images, and NASA’s Nancy Grace Roman Space Telescope, which lifted off from Kennedy Space Center in late August, are both expected to supply tens of thousands of additional supernovae over the next decade, along with sharper galaxy-clustering measurements from DESI. Those larger samples, plus additional low-redshift supernovae researchers plan to fold into the standardized catalogs, should determine whether today’s hint of a changing dark energy strengthens into a firm discovery or fades back into statistical noise.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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