The largest collection of exploding white dwarf stars ever compiled is providing fresh evidence that dark energy, the mysterious force responsible for the Universe’s accelerating expansion, may change over time. The findings challenge a central assumption of modern cosmology and could help scientists better understand how the Universe evolves. An international research team led by scientists at the University of Queensland’s School of Mathematics and Physics brought together observations of 2,884 Type Ia supernovae.
These powerful stellar explosions serve as important tools for measuring distances across the Universe, allowing astronomers to trace its expansion history. PhD candidate Ryan Camilleri said the project establishes a new international standard for supernova cosmology. By bringing decades of measurements into a unified dataset, researchers have created their most detailed picture yet of how cosmic expansion has changed over time.
To make observations collected over different periods directly comparable, the scientists revisited older data using updated analytical methods. Advances in understanding supernova behavior allowed the team to improve the consistency and accuracy of measurements gathered over decades. The researchers also had to account for differences among the telescopes used to collect the observations.
Other factors, including cosmic dust and the masses of galaxies, can influence the light astronomers receive from distant supernovae and therefore affect distance measurements. Under the standard model of cosmology, dark energy is treated as a constant property of the Universe. However, recent observations have raised questions about whether that assumption fully explains how cosmic expansion has evolved.
The findings are especially interesting because a separate astronomical project has also produced evidence suggesting that dark energy might not remain constant. Although the different measurements do not point to exactly the same departure from the standard model, they provide additional reasons to investigate whether dark energy changes as the Universe ages. Understanding dark energy could have implications extending far beyond the expansion of the Universe.
Researchers believe that learning more about its behavior might also provide insights into one of the greatest unresolved problems in theoretical physics: reconciling gravity with quantum physics. One important source will be the Dark Energy Bedrock All-Sky Supernova program (DEBASS), which is identifying hundreds of supernovae at distances closer to Earth than those surveyed by DES. Incorporating these nearby explosions will provide further measurements that scientists can use to investigate the Universe’s expansion and test whether dark energy truly changes over time.
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