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yesterday

Rebuttal Confirms Cosmic Expansion Is Still Accelerating

A peer-reviewed MNRAS paper finds calibration errors in a 2025 Yonsei analysis, restoring confidence in supernova-based dark energy measurements.

Studying Type Ia supernovae – violent, luminous white dwarf star explosions – led to the Nobel Prize-winning discovery that the universe’s expansion is accelerating. This image combines data from four space telescopes to create a multi-wavelength view of all that remains of RCW 86, the oldest documented example of a supernova. (Credit: X-ray: NASA/CXC/SAO & ESA; Infared: NASA/JPL-Caltech/B. Williams (NCSU))
Stars at the center of the Milky Way galaxy, via the Spitzer Space telescope - credit NASA, JPL-Caltech, S Stolovy (SSCCaltech). Image Credit: NASA, JPL-Caltech, S Stolovy (SSC/Caltech).

Overview

  • The University of Southampton-led team published a paper on Thursday, June 11, 2026, concluding that Type Ia supernova data still imply an accelerating universe when correctly calibrated.
  • The authors identified two specific methodological faults in the 2025 Yonsei study: it equated a host galaxy's age with the exploding star's progenitor age and omitted the standard host-galaxy mass correction.
  • When those errors are corrected and supernovae are calibrated for host environment and population, the mathematical evidence for cosmic acceleration remains robust, the paper reports.
  • The rebuttal, published in Monthly Notices of the Royal Astronomical Society and co-authored by Nobel laureates Adam Riess and Brian Schmidt, has prompted a Yonsei response on arXiv and ongoing technical exchanges between the teams.
  • Researchers say the episode will sharpen methods rather than overturn dark energy work, refocusing efforts on better progenitor and host-environment models to tighten constraints on why expansion is accelerating.