Nearly 3,000 Exploding Stars Add Weight to the Idea That Dark Energy Shifts

The largest collection of exploding white dwarf stars ever assembled offers fresh evidence that dark energy, the mysterious force speeding up the expansion of the Universe, may not be constant, according to ScienceDaily. The finding is a hint, not a proof, but it pushes against a central assumption of standard cosmology.

An international team led by scientists at the University of Queensland combined observations of 2,884 Type Ia supernovae. These stellar explosions help astronomers measure distances across the Universe, which in turn lets them trace how its expansion has changed over time.

What the researchers did

The team pulled together three decades of supernova measurements, along with results from the Dark Energy Survey (DES) published in 2024. PhD candidate Ryan Camilleri said the project rebuilt those decades of observations into one consistent framework and sets a new international standard for supernova cosmology.

That took considerable work. Older data were reanalyzed using what scientists have since learned about how supernovae behave. The team also had to link observations from different telescopes and correct for cosmic dust and the masses of galaxies, both of which can alter the light that reaches Earth. They even included subtler effects such as gravitational lensing, the bending and magnification of light by large objects on its way from a supernova to us.

The supernova data were then combined with other cosmic measurements, including relic light from the Big Bang and maps of how galaxies are spread through space.

Why the result is notable

The standard model of cosmology treats dark energy as a fixed, unchanging property of the Universe. Camilleri said the combined analysis did not confirm that picture and instead added evidence that dark energy may change over time.

Professor Tamara Davis, an astrophysicist on the project, noted that the 2024 DES supernova data first showed hints of time-varying dark energy. The new compilation also departs from the standard model, she said, although in a slightly different direction.

A separate effort points the same way. Davis said the Dark Energy Spectroscopic Instrument (DESI) found hints of variation in dark energy in its surveys of relic sound waves from the early Universe. She described the two measurements as completely independent. They do not show exactly the same departure from the standard model, but together they give scientists more reason to ask whether dark energy changes as the Universe ages.

Why it matters beyond cosmology

Dark energy is one of the biggest open questions in physics, and the researchers say it may connect to another. Davis said the work could hold a clue to how gravity and quantum physics fit together, two theories that each succeed in their own realms. Joining them, she said, would be a huge step in theoretical physics.

Nothing here changes everyday life, and the results do not settle the question. The team describes the evidence as pointing toward time variation, and the two datasets do not agree on its exact form.

What comes next

The researchers plan to expand the dataset as more observations arrive. One important addition will be the Dark Energy Bedrock All-Sky Supernova program (DEBASS), which is identifying hundreds of supernovae closer to Earth than those surveyed by DES. Including these nearby explosions will give scientists more measurements for testing whether dark energy truly changes.

The cosmology findings and a companion set of host galaxy mass measurements are available on the preprint server arXiv. The new results build on the work of hundreds of astronomers and researchers around the world.

Around Prague, based on reporting by ScienceDaily