An international team of astronomers and cosmologists has produced the most precise measurement to date of the universe's expansion rate [1, 2].
This discovery is critical because it addresses the Hubble tension, a persistent discrepancy between how fast the universe appears to have expanded in its infancy versus its current state. Resolving this gap is essential for physicists to understand the fundamental laws governing the cosmos.
Researchers achieved this measurement in April 2026 by observing a rare, super-luminous supernova nicknamed "SN Winny" [3]. The supernova is located approximately 10 billion light-years away [3]. By using this distant celestial event as a cosmic yardstick, the team was able to calculate the Hubble constant, the unit used to describe the expansion rate of the universe, with unprecedented accuracy [2, 3, 4].
The new data indicates a late-universe expansion rate of approximately 73 km s⁻¹ Mpc⁻¹ [2]. This measurement carries a margin of error of roughly one percent [2].
This result starkly contrasts with estimates based on the cosmic microwave background, which represents the early universe. Those earlier measurements typically place the Hubble constant in the high 60s km s⁻¹ Mpc⁻¹ [4].
The gap between these two figures suggests that the universe may be expanding faster than current theoretical models predict [1]. Because the new measurement is so precise, it reduces the likelihood that the discrepancy is simply a result of observational error. Instead, the tension implies that there may be unknown physics at play or an incomplete understanding of dark energy, the mysterious force driving the acceleration of the universe [4].
“The new data indicates a late-universe expansion rate of approximately 73 km s⁻¹ Mpc⁻¹.”
The confirmation of a higher expansion rate through the observation of SN Winny suggests that the 'Hubble tension' is a physical reality rather than a measurement error. This indicates that the standard model of cosmology may be incomplete, potentially requiring new physics to explain why the late universe is expanding faster than the early universe's data predicted.
