A recent study suggesting that the Universe is decelerating has drawn critical attention from prominent astrophysicists, including Nobel Prize winner Adam Reiss. Reiss, who received the 2011 Nobel Prize in Physics alongside Saul Perlmutter and Brian Schmidt for discovering the accelerating expansion of the Universe, has identified significant flaws in the claims made in the paper.
The study, which is part of a growing discourse on cosmic expansion, is based on observations of approximately 300 supernovae. The authors argue that there is a correlation between the peak brightness of Type-Ia supernovae and the age of their host galaxies. They contend that younger galaxies exhibit dimmer supernovae, leading to the conclusion that our measurements of cosmic distances are inaccurate and suggesting a decelerating Universe that contradicts the widely accepted ΛCDM model.
Despite being peer-reviewed, Reiss points out critical issues in the paper’s methodology. He highlights that while the authors claim that Type-Ia light curves do not consider the ages of their host galaxies, this assertion is only partially correct. Modern astrophysical models take into account galactic mass, which correlates strongly with age. The age determination of a galaxy is complex and model-dependent, making it a less reliable metric compared to mass.
Since around 2010, most Type-Ia supernova catalogs, including the significant Pantheon+ database, have incorporated mass adjustments. This adjustment serves as a proxy for age, indicating that once mass is factored in, adjusting for age does not significantly alter the results. Reiss criticizes the authors for using outdated databases that lack this crucial mass adjustment, calling this a potential red flag in their research.
Another point raised by Reiss concerns the relationship between host galaxy age and the age of supernova progenitors. The authors focus on the measured age of the host galaxies, assuming that progenitor stars formed concurrently with the galaxies. This leads them to suggest that distant supernovae progenitors are younger than those of nearby supernovae. However, research indicates that Type-Ia supernovae typically occur less than a billion years after their progenitor stars form, complicating the authors’ argument.
Reiss urges caution and encourages further examination of these claims. He anticipates forthcoming peer-reviewed papers that will delve into these issues and provide a more robust analysis of the findings.
As the scientific community continues to engage with this controversial research, the implications of these discussions could reshape our understanding of cosmic expansion.
This ongoing dialogue highlights the importance of rigorous analysis in astrophysics, ensuring that conclusions about the Universe’s behavior are accurate and well-supported.
The original study is documented in the paper titled “Strong progenitor age bias in supernova cosmology–II. Alignment with DESI BAO and signs of a non-accelerating universe,” published in the *Monthly Notices of the Royal Astronomical Society*. Additional references include studies on supernova brightness and host galaxy mass in *The Astrophysical Journal*.
With thanks to Professor Reiss for his insightful contributions to this discourse.
