Yonsei University’s research team, led by Professor Young-Wook Lee of the Center for Galaxy Evolution, has directly challenged the “accelerating expansion of the universe” theory, which was the basis for the 2011 Nobel Prize in Physics. The team recalibrated supernova observation data and concluded that the universe is now entering a deceleration phase.
On the 16th, Yonsei University announced that the team had published the findings in the Monthly Notices of the Royal Astronomical Society (MNRAS), challenging the established cosmological model that has been widely accepted since the discovery of dark energy in 1998.
The research team demonstrated with a 5.5-sigma (99.9999999%) confidence level that the brightness of supernovae varies according to the age of the exploding stars. Supernovae originating from older stars tend to be significantly brighter.
By incorporating this variable, the research results no longer aligned with the existing standard model where dark energy exists as a cosmological constant. The study involved the analysis of approximately 300 supernova host galaxies. Professor Lee explained, “The modified supernova data shows that the universe has already entered a decelerating expansion stage,” adding, “This aligns with predictions from baryon acoustic oscillations alone or combined with cosmic microwave background analysis.”
The research team continues to conduct an “evolution-free” cosmological test using only young galaxies of the same age across all redshift ranges to more directly verify their previous findings. Jeong-Chul, a research professor at Yonsei University, stated that measuring the ages of approximately 20,000 new supernova host galaxies, expected to be discovered by the Large Synoptic Survey Telescope (LSST) within five years, will enable more precise cosmological research.
The academic community believes that if these results are conclusively verified, it could potentially lead to a paradigm shift in cosmology for the first time in 27 years since the discovery of dark energy in 1998. This could provide clues to fundamental problems such as the nature of dark energy, the Hubble tension, and the history of the universe’s expansion.
This research was supported by the National Research Foundation of Korea and involved collaborative participation from researchers Junhyuk Son and Seunghyun Park, as well as research professors Jeong-Chul and Hyejeon Cho.