Observations of the fine structure constant in sources such as supernovae and quasars suggest apparent variations, typically ascribed to observational -uncertainties. Likewise, the persistent Hubble tension—between the CMB-inferred value \((\varvec{H}_{\varvec{0}} \varvec{\approx } \varvec{67.4}\) km/s/Mpc) and direct measurements ( \(\varvec{H}_{\varvec{0}} \varvec{\approx } \varvec{73}\) km/s/Mpc)—remains unresolved. Additionally, quasars often display higher redshifts than their host galaxies, contrary to expectations from standard cosmology. A previous study (Postavaru and Craciun, Int. J. Mod. Phys. D, 33(09n10), 2450033, 2024) proposed that the speed of light increases above a critical temperature \(\varvec{T}_{\varvec{c}} \varvec{=} \varvec{4} \varvec{\times } \varvec{10}^{\varvec{9}}\,{\varvec{\textrm{K}}}\) . We extend this idea, showing that high-temperature sources—such as quasars, supernova cores, and GRBs—emit photons with an intrinsic thermal redshift that mimics cosmological redshift under constant-c assumptions. This reinterpretation reproduces the observed Hubble diagram without requiring dark energy, resolving the Hubble tension. Our model accounts for luminosity distance observations from supernovae, GRBs, and quasars and remains consistent with recent JWST results. Since atomic transitions are absent at \(\varvec{T} \varvec{\gg } \varvec{T}_{\varvec{c}}\) , we also introduce a luminosity-based method for estimating source temperatures, enabling a unified treatment of high-temperature astrophysical phenomena.
