Astronomers Precisely Measure Universe's Expansion Rate, Hubble Tension Persists

New study combines decades of observations to provide the most accurate local expansion rate yet, but discrepancy with early Universe predictions remains unresolved.

Apr. 11, 2026 at 7:34am

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A highly textured, abstract painting in earthy tones of ochre, sage, and indigo, featuring sweeping geometric arcs, concentric circles, and precise botanical spirals, conceptually representing the complex forces and structures underlying the expansion of the Universe.A groundbreaking study combines decades of observations to precisely measure the local expansion rate, but the persistent discrepancy with early Universe predictions remains a cosmological mystery.Tucson Today

An international collaboration of astronomers has produced one of the most precise measurements yet of how fast the local Universe is expanding. The result deepens one of the most significant challenges in modern cosmology, known as the Hubble tension, where measurements based on the nearby Universe consistently indicate a higher expansion rate compared to predictions derived from the early Universe.

Why it matters

The Hubble tension has now been observed across multiple independent studies and techniques, suggesting the standard model of cosmology may be incomplete. If the discrepancy is real, it could point to new physics beyond the current model, such as the behavior of dark energy or the need for modifications to gravity.

The details

The study, led by the H0 Distance Network (H0DN) Collaboration, reports a value of the Hubble constant of 73.50 ± 0.81 kilometers per second per megaparsec, corresponding to a precision of just over 1%. This was achieved by bringing together decades of independent observations into a single, unified framework that links many overlapping techniques for measuring distances across the local Universe, including observations of pulsating Cepheid variable stars, red giant stars, Type Ia supernovae, and certain types of galaxies.

  • The study was published on April 10, 2026 in the journal Astronomy & Astrophysics.
  • The collaboration was launched at the International Space Science Institute (ISSI) Breakthrough Workshop, "What's under the H0od?", held in Bern, Switzerland in March 2025.

The players

John Blakeslee

An astronomer and Director of Research and Science Services at NSF NOIRLab, who is a member of the H0DN Collaboration.

NSF NOIRLab

The U.S. National Science Foundation center for ground-based optical-infrared astronomy, which contributed both expertise and observational data from its Cerro Tololo Inter-American Observatory (CTIO) in Chile and Kitt Peak National Observatory (KPNO) in Arizona to the collaborative effort.

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What’s next

With next-generation observatories expected to provide even more precise measurements, astronomers aim to determine whether this discrepancy will ultimately be resolved or continue to point toward new physics.

The takeaway

The persistent Hubble tension, where local and early Universe measurements of the expansion rate disagree, suggests the standard cosmological model may be incomplete. This could signal the need for new physics, such as undiscovered properties of dark energy or modifications to gravity, which could fundamentally change our understanding of the Universe's evolution.