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Gravitational-Lens Time Delays Deliver New Hubble Constant, Deepening the Tension

A TDCOSMO analysis of eight lensed quasars measures 71.6 km/s/Mpc with 4.5% precision, pointing to larger samples to reach decisive 1–2% tests.

Overview

  • The peer-reviewed Astronomy & Astrophysics study finds H0 = 71.6 (+3.9/−3.3) km/s/Mpc via time-delay cosmography, consistent with late-universe values yet offset from CMB-inferred ~67.
  • Eight strong gravitational lenses were modeled using long-term photometric delays and stellar-kinematic spectroscopy from JWST, Keck, VLT, and Hubble to tackle dominant systematics.
  • Uncertainty in the lens galaxies’ mass distribution remains the leading limitation, keeping the current precision near 4.5%.
  • The collaboration plans to enlarge the lens sample and refine mass models to approach 1–2% precision that could clarify whether the mismatch signals new physics.
  • A separate Yonsei University study claims an age-related bias in Type Ia supernova brightness that could affect distance-ladder results, with LSST and Euclid expected to provide crucial tests.