A record 2,884 exploding stars are giving astronomers a fresh way to test what is driving the Universe’s growth. The stars are Type Ia supernovae: powerful explosions of white dwarfs whose brightness helps scientists measure distances across space.
That matters because the Universe is expanding faster over time, and scientists attribute this acceleration to dark energy. The leading model of cosmology treats dark energy as constant. But if it changes as the Universe ages, that model may need to be revised. An international team led by researchers at the University of Queensland’s School of Mathematics and Physics has assembled the largest collection of these supernova observations yet, bringing decades of measurements into one consistent dataset.
The team combined earlier records with results from the Dark Energy Survey, published in 2024. Researchers revisited older observations using improved knowledge of how supernovae behave, then worked to make measurements from different telescopes comparable. They also accounted for cosmic dust and galaxy mass, which can change the light reaching Earth. Another factor was gravitational lensing, the bending and magnifying of light by massive objects along its path.
The team compared the supernova evidence with other measures of the cosmos, including relic light left from the Big Bang and maps of how galaxies are spread through space. PhD candidate Ryan Camilleri said the compilation offers the most detailed picture yet of how cosmic expansion has changed over time. Rather than confirming that dark energy stays fixed, the combined analysis found further evidence that it may vary.
The result is a clue, not a final answer. The new supernova compilation points away from the standard model in a slightly different direction than the Dark Energy Survey’s 2024 results did. A separate project, the Dark Energy Spectroscopic Instrument, or DESI, has also found hints of variation by studying ancient sound-wave patterns in the Universe. These independent measurements do not show exactly the same departure from the standard model, but both give researchers reason to test whether dark energy changes over time.
That question reaches beyond the history of cosmic expansion. A better understanding of dark energy could offer insights into how gravity fits with quantum physics, two powerful theories that describe nature in very different ways but have yet to be joined into one complete picture.
The researchers plan to add more observations as they become available. One source will be the Dark Energy Bedrock All-Sky Supernova program, known as DEBASS, which is finding hundreds of supernovae at closer distances. More consistent measurements, combined with other cosmic surveys, may help scientists tell whether the hints point to a real change in dark energy—or whether the standard model still holds.