Overview
- Two peer‑reviewed papers published in June 2026 analyzed the same Pantheon+ compilation and reached directly opposing results about cosmic expansion.
- A team led by Phil Wiseman (University of Southampton) found that applying the long‑used host‑galaxy mass correction and revising progenitor‑age estimates restores the standard picture of a uniformly accelerating universe driven by dark energy.
- A separate paper by Animesh Sah, Mohamed Rameez and Subir Sarkar (Tata Institute/Oxford) applied a progenitor‑age correction to Pantheon+ and reported that the data instead favour overall deceleration and a directional (anisotropic) signal.
- The core disagreement is methodological: age‑based corrections require reliable progenitor or host‑galaxy ages for distant supernova hosts, data that currently exist for only a minority of cases and so make age corrections controversial.
- Both teams say much larger, uniform supernova samples from surveys such as the Rubin Observatory’s LSST and cross‑checks with CMB and BAO measurements are the clear next step to settle whether dark energy is real and isotropic.