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7h ago

Rebuttal Confirms Universe Is Still Accelerating

The paper identifies calibration errors in the contested South Korean analysis, clearing the way to renew efforts to measure dark energy's properties.

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))

Overview

  • The University of Southampton–led rebuttal was published Thursday in Monthly Notices of the Royal Astronomical Society and directly challenges a November 2025 South Korean study that claimed recent cosmic deceleration.
  • Lead author Dr Phil Wiseman and co-authors including Adam Riess and Brian Schmidt found the earlier paper wrongly assumed a galaxy's age equals the exploding star's age, which biased its brightness calibration.
  • The rebuttal also shows the South Korean team omitted a standard host-galaxy mass correction, a routine adjustment that affects Type Ia supernova brightness measurements.
  • When supernovae are recalibrated for progenitor age differences and host-galaxy mass, the data remain consistent with ongoing cosmic acceleration driven by dark energy.
  • The episode prompted detailed method checks that strengthen confidence in supernova cosmology and lets researchers refocus on improving measurements to probe what dark energy actually is.