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Loading contentThe programme that measures the Hubble constant from the local distance ladder — anchoring Cepheids with parallax, using them to calibrate Type Ia supernovae, and reading the expansion rate from supernovae in the smooth Hubble flow. Its value comes out consistently higher than the one inferred from the early universe, and that gap is the Hubble tension.
Facts on this topic will be cited from these primary and reference sources.
Science operations and public image archives for the Hubble and James Webb space telescopes (MAST, HubbleSite, webbtelescope.org).
Hubble/Webb images released by NASA/STScI are generally free to use with a credit line; each item's terms are checked before use.