Hubble tension remains unresolved after most thorough local-universe study

A community-built Local Distance Network measured the local Hubble constant at 73.50 km/s/Mpc with a 1.09% uncertainty and found the discrepancy with early-universe CMB measurements (about 67–68 km/s/Mpc) still persists.

A collaborative study combined decades of independent distance measurements into a unified Local Distance Network and reported a very precise local measurement of the universe's expansion. The paper, published April 10 in Astronomy & Astrophysics, found a local Hubble constant of 73.50 kilometers per second per megaparsec with a relative uncertainty of 1.09%. This value remains inconsistent with early-universe measurements from the cosmic microwave background, which are near 67–68 km/s/Mpc. The work grew from a community effort centered at the International Space Science Institute Breakthrough Workshop in Bern in March 2025. Key findings: - The Local Distance Network combined observations of more than 7,500 galaxies and multiple local anchors such as NGC 4258, the Magellanic Clouds, and variable stars. - The study derived a local Hubble constant of 73.50 km/s/Mpc with a relative uncertainty of 1.09%. - Early-universe CMB-based measurements continue to give about 67–68 km/s/Mpc, producing the Hubble tension. - Leave-one-out analyses showed minimal change when individual measurement techniques, such as Cepheid-based distances, were excluded. - The paper was published April 10 in Astronomy & Astrophysics following the Bern workshop that helped set the framework. Summary: The persistence of the Hubble tension suggests current cosmological models do not fully explain the measured expansion rates and may point to new physics, including ideas mentioned by the authors such as primordial magnetic fields. Undetermined at this time.