A recent paper suggesting that the Universe is decelerating has sparked significant debate in the scientific community. Adam Reiss, who won the 2011 Nobel Prize in Physics alongside Saul Perlmutter and Brian Schmidt for his work on the accelerating expansion of the Universe, raised several concerns regarding the paper’s methodology and conclusions.
The original study, based on observations of approximately 300 Type-Ia supernovae, claims to correlate the peak brightness of these supernovae with the age of their host galaxies. The authors argue that younger galaxies produce dimmer supernovae, leading to a miscalculation of galactic distances. According to their findings, this implies that the Universe is decelerating and challenges the widely accepted ΛCDM model, which describes the Universe’s expansion.
Despite being peer-reviewed, Reiss identifies critical flaws in the paper’s arguments. One major issue lies in how the authors address the age of galaxies. While they maintain that the light curves of Type-Ia supernovae do not account for the ages of their host galaxies, Reiss points out that these light curves do consider galactic mass—a more straightforward measurement. The determination of a galaxy’s age is complex and often model-dependent, which can affect results.
Modern catalogs, such as Pantheon+, adjust for mass because studies indicate that a supernova’s host galaxy’s mass is a reliable proxy for its age. Reiss emphasizes that since around 2010, Type-Ia supernova catalogs have included mass adjustments, which mitigate the need to consider age directly. The authors of the deceleration paper, however, relied on older data that did not incorporate these adjustments, raising questions about their methodology.
Another significant concern raised by Reiss is the assumption made by the authors regarding the age of supernova progenitors. While they use the measured age of the host galaxies as a proxy for the progenitor stars, this method is flawed. The paper assumes that progenitor stars formed concurrently with their host galaxies, implying that distant supernova progenitors are younger than those nearby. However, many studies show that Type-Ia supernovae typically occur less than a billion years after the formation of their progenitor stars, suggesting that the authors’ foundational argument is weak.
As the discussion surrounding this controversial study continues, Reiss suggests that further peer-reviewed research will address these issues in greater depth. The scientific community eagerly anticipates forthcoming publications that will evaluate the claims made in the original paper.
Reiss’s insights highlight the importance of robust methodologies in astrophysical research, especially when challenging established theories. The debate over cosmic expansion remains a pivotal topic in contemporary astronomy, with implications that could reshape our understanding of the Universe.
The original study, titled “Strong progenitor age bias in supernova cosmology–II. Alignment with DESI BAO and signs of a non-accelerating universe,” was published in the Monthly Notices of the Royal Astronomical Society. Other relevant studies include “It’s dust: solving the mysteries of the intrinsic scatter and host-galaxy dependence of standardized type Ia supernova brightnesses,” and “Host Galaxy Mass Combined with Local Stellar Age Improve Type Ia Supernovae Distances,” both published in The Astrophysical Journal.
