Cosmic Acceleration May Be an Illusion, Cosmology Faces a Fresh Challenge

New analysis of Type Ia supernovae data, with progenitor-age corrections from the Pantheon+ catalog, suggests the universe’s expansion may be mildly anisotropic and not accelerating uniformly in all directions. If younger supernova progenitors are fainter after standardization, distant observations could mimic acceleration, meaning the apparent cosmic acceleration could be a local, directional effect tied to our motion through the cosmos. This challenges the isotropy assumed in ΛCDM and raises doubts about dark energy's role, while also intersecting with the ongoing Hubble tension between local and early-universe expansion rates.