An international team of astronomers has assembled the largest catalogue of exploding white dwarf stars ever compiled, and the result adds fresh weight to a provocative idea: dark energy, the mysterious force driving the universe's accelerating expansion, may not be constant after all.
Led by researchers at the University of Queensland, the project combined observations of 2,884 Type Ia supernovae — standardised stellar explosions astronomers use as distance markers to trace the universe's expansion history — gathered across three decades of surveys, including the Dark Energy Survey, the Sloan Digital Sky Survey and the Supernova Legacy Survey.
Thirty years of data, rebuilt from scratch
"We've rebuilt three decades of astronomical observations into a single, consistent framework," said PhD candidate Ryan Camilleri, who worked on the project. Researchers revisited older measurements using updated analytical techniques, accounting for differences between telescopes, cosmic dust, galaxy mass and gravitational lensing effects that can distort the light reaching Earth from a distant supernova.
The standard model of cosmology treats dark energy as an unchanging property of the universe. But this compilation — like the Dark Energy Survey's 2024 results before it — found a deviation from that assumption, albeit in a slightly different direction. "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," said astrophysicist Professor Tamara Davis.
Crucially, a separate and unrelated project, the Dark Energy Spectroscopic Instrument, has independently found its own hints that dark energy varies, based on entirely different measurements of relic sound waves from the early universe. "Two completely independent measurements have found hints of time variation in dark energy, challenging the standard model," Davis said.
Researchers say resolving the question could carry implications well beyond cosmology, potentially offering clues toward reconciling gravity with quantum physics — a long-standing unsolved problem in theoretical physics. The team plans to expand its dataset further through a new survey, DEBASS, which is identifying supernovae closer to Earth than those captured by the Dark Energy Survey.