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Peer-Reviewed Study Says Universe’s Expansion Has Begun to Slow After Supernova Age Correction

A Yonsei-led analysis says adjusting supernova distances for progenitor age yields results consistent with BAO and CMB probes.

Overview

  • The paper in Monthly Notices of the Royal Astronomical Society reports no present-day acceleration, suggesting the universe has entered a decelerating phase.
  • Researchers identify a strong progenitor age-bias in Type Ia supernovae using about 300 host galaxies, quantified at 99.999% confidence.
  • After applying the age correction, supernova data no longer support the standard ΛCDM model with a cosmological constant.
  • The corrected supernova results align with BAO- and CMB-based analyses, including patterns highlighted by the DESI project that imply time-varying dark energy.
  • Authors say a combined analysis with corrected supernovae, BAO and CMB disfavors ΛCDM with overwhelming significance, while noting independent tests with larger samples are underway, including an evolution-free approach and forthcoming Rubin Observatory data.