A massive compilation of astronomical observations involving nearly 3,000 exploding stars is providing new evidence that dark energy, the mysterious force driving the Universe’s accelerating expansion, may not be constant. The findings, led by researchers at the University of Queensland, challenge a central pillar of modern cosmology and suggest that the nature of the Universe evolves more dynamically than previously assumed.
Unified Supernova Dataset Reveals Deviations
The international team, which includes scientists from the University of Queensland’s School of Mathematics and Physics, assembled the largest collection of Type Ia supernovae ever recorded. These stellar explosions occur when white dwarf stars reach a critical mass and detonate. Because they explode with a consistent brightness, astronomers use them as standard candles to measure vast cosmic distances and trace the history of the Universe’s expansion.
The dataset combines 2,884 supernova observations, merging historical measurements with data from the Dark Energy Survey (DES) published in 2024. To ensure accuracy, the researchers applied modern analytical methods to decades-old data. This process accounted for variables that can skew distance measurements, such as cosmic dust, the mass of host galaxies, and gravitational lensing, which bends light around massive objects.
PhD candidate Ryan Camilleri, who led the data integration, stated that the project establishes a new international standard for supernova cosmology. By creating a single, consistent framework from disparate sources, the team produced the most detailed picture yet of how cosmic expansion has shifted over billions of years.
“We’ve rebuilt 3 decades of astronomical observations into a single, consistent framework,” Camilleri said. “We combined our data with other cosmic measurements including relic light from the Big Bang and maps of how galaxies are distributed through space.”
Challenging the Standard Cosmological Model
The standard model of cosmology treats dark energy as a fixed property of space, often referred to as the cosmological constant. Under this model, the density of dark energy remains unchanged as the Universe expands. However, the new analysis indicates a deviation from this assumption. The data suggests that dark energy may vary over time, a finding that aligns with hints from other independent projects.
Professor Tamara Davis, an astrophysicist involved in the study, noted that the DES data from 2024 first showed signs that dark energy might be time-varying. The new compilation reinforces this deviation, although the specific pattern of change differs slightly from earlier reports. This convergence of evidence is significant because it comes from two completely independent measurement techniques.
Separately, the Dark Energy Spectroscopic Instrument (DESI) has also found hints of variation in dark energy by surveying relic sound waves from the early Universe. While the two projects do not point to the exact same departure from the standard model, the combined results provide strong reasons to investigate whether dark energy evolves as the Universe ages.
“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,” Professor Davis said.
Implications for Physics and Future Research
If dark energy is not constant, it could reshape our understanding of fundamental physics. Researchers believe that clarifying the behavior of dark energy may help solve one of the greatest problems in theoretical physics: reconciling gravity with quantum mechanics. These two theories are highly successful in their respective domains but have resisted unification for decades.
The study builds on contributions from hundreds of astronomers worldwide. Projects that provided data include the Foundation Supernova Survey, PanStarrs I, the Sloan Digital Sky Survey, the Supernova Legacy Survey, the Carnegie Supernova Project, and the Center for Astrophysics supernova survey.
The research team plans to expand the dataset as new observations become available. A key 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 allow scientists to test the expansion history with greater precision.
The cosmology findings are available on arXiv, with accompanying measurements of host galaxy masses also published on the preprint server. The work continues to refine the tools used to map the Universe, pushing the boundaries of how we understand its past and future.
Source: ScienceDaily
