Overview
- Yonsei University researchers report that correcting for a progenitor-age bias in about 300 Type Ia supernova hosts implies the universe has entered a decelerating phase and that dark energy varies over time.
- The team says older stellar populations yield intrinsically brighter explosions than younger ones, arguing this undermines the assumption that supernovae are perfect standard candles for distance measurements.
- Authors cite very high statistical confidence and note consistency with BAO and CMB indicators, echoing DESI findings that galactic acceleration has changed over cosmic time.
- Senior cosmologists, including George Efstathiou, dispute the interpretation as likely due to supernova systematics, keeping the community cautious pending independent reanalyses.
- The study appears in MNRAS, the team is conducting an evolution-free test using same-age hosts, and the Vera C. Rubin Observatory’s expected ~20,000 supernova hosts over five years are seen as decisive; a future Big Crunch is discussed as a possibility if dark energy keeps weakening.