Study Suggests Universe May Be Decelerating Based on Corrected Supernova Data
A new analysis of the Pantheon+ Type Ia supernova catalogue, applying corrections for the age-dependent luminosity evolution of supernova progenitors, finds that the universe's deceleration parameter shifts to positive values — implying deceleration rather than the acceleration that underpins dark energy. The study builds on prior work showing a strong local dipole anisotropy in the deceleration parameter aligned with the cosmic bulk flow, and finds that monopole component — the globally averaged signal — flips sign once progenitor age effects are accounted for. If confirmed, this would challenge the foundational observational evidence for dark energy and the standard ΛCDM cosmological model.
Researchers led by Subir Sarkar have reanalyzed the Pantheon+ Type Ia supernova dataset — one of the primary observational pillars supporting cosmic acceleration and dark energy — by applying redshift-dependent corrections for the age of supernova progenitor systems. Their cosmographic analysis finds that once these luminosity evolution effects are removed, the monopole component of the deceleration parameter q₀ becomes positive, indicating the universe is decelerating rather than accelerating. The local dipole anisotropy in q₀, previously identified as strongly aligned with the cosmic bulk flow direction, remains essentially unchanged by the correction. The result directly challenges the standard interpretation of supernova data as evidence for a cosmological constant (Λ) or dark energy. The paper is a 5-page Letter accepted for publication in Monthly Notices of the Royal Astronomical Society, a peer-reviewed journal, lending it meaningful credibility, though it has not yet undergone broad community scrutiny. The core claim hinges on the validity and magnitude of the progenitor age correction applied, which remains a debated systematic in supernova cosmology. If the findings hold up, they would represent a significant revision to the observational case for accelerating cosmic expansion first established in 1998.
What's missing
The paper does not compare the progenitor age correction against alternative systematic correction schemes, making it difficult to assess how sensitive the sign-flip in q₀ is to the choice of correction. The broader community's response and any independent replication are absent. Additionally, the paper's relationship to other supernova datasets beyond Pantheon+ (e.g., Union, DES) and whether the same correction would yield consistent results there is not addressed.
What different sources said
- arXiv astro-phCenter
Pantheon+ supernovae corrected for progenitor age indicate the universe is decelerating
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