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This research explores how light propagation biases from the heliosphere may influence local distance measurements leading to the Hubble tension.

May 29, 2026

Systematic Light Propagation Bias from the Heliosphere and Its Impact on the Hubble Tension

Key Points

This research explores how light propagation biases from the heliosphere may influence local distance measurements leading to the Hubble tension.
Performed theoretical calculations analyzing the influence of heliospheric effects on distance measurements.
Evaluated contributions from particles and thermal gradients in the solar system's environment.
Discussed observational tests to validate the proposed hypothesis.
Heliospheric effects could account for ~8% of the observed discrepancy in Hubble constant measurements.
Realistic contributions are estimated to be in the ~3-8% range after considering variables like anisotropy and calibration cancellation.
The findings indicate a significant bias that may affect the cosmic distance ladder outcomes.

Abstract

The Hubble tension (HT) represents one of the most significant discrepancies in modern cosmology, with local distance measurements yielding H 0 = 73.5 ± 1.4 km/s/Mpc while cosmic microwave background (CMB) observations predict H 0 = 67.4 ± 0.5 km/s/Mpc. We propose that this tension arises from systematic effects introduced by our Solar System’s heliospheric (HS) environment on local distance measurements. The HS creates a complex medium of heated plasma and energetic neutral atoms (ENAs) beyond the heliopause (HP), where interstellar medium (ISM) temperatures rise significantly. This thermal gradient and particle environment may systematically affect observations of Cepheid variables and Type Ia supernovae (SNe Ia) used in the local cosmic distance ladder (CDL), biasing distance measurements and artificially inflating the measured Hubble constant. We present theoretical calculations showing how HS effects could account for up to ~ 8% of the observed 8–9% discrepancy, with the realistic contribution lying in the ~ 3–8% range once anisotropy, partial calibration cancellation, and chromatic suppression are included, and discuss observational tests to validate this hypothesis.

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