Astrophysicists Propose New Method to Measure Hubble Constant

Astrophysicists from the University of Illinois and the University of Chicago have developed an innovative method to measure the Hubble constant – the rate at which the Universe is expanding – using the subtle hum of gravitational waves. As gravitational wave detectors become more sensitive in the coming years, this approach could reshape our understanding of cosmic history and help resolve a central debate in modern astrophysics.

Diagram of the expansion of the Universe from the Big Bang to the present day. Image credit: NASA / EFBrazil.

“This result is very significant: it is important to obtain an independent measurement of the Hubble constant to resolve the current Hubble tension,” said Professor Nicolás Yunes from the University of Illinois.

“Our method is an innovative way to improve the accuracy of Hubble constant inferences using gravitational waves.”

Professor Yunes and his colleagues propose a gravitational wave-based technique that exploits the faint “background hum” from countless distant black hole collisions to refine estimates of the Hubble constant.

Unlike traditional methods, this new approach exploits ripples in space-time itself – gravitational waves – which carry information about the vast distances and speed at which objects are moving away.

Astrophysicists call this the “stochastic siren” method.

“Because we observe individual black hole collisions, we can determine the rates of these collisions occurring across the Universe,” said University of Illinois graduate student Bryce Cousins.

“Based on these rates, we expect there to be many more events that we cannot observe, the so-called gravitational wave background.”

“It’s not every day that we come up with an entirely new tool for cosmology,” added Professor Daniel Holz of the University of Chicago.

“We show that using the hum of background gravitational waves from merging black holes in distant galaxies, we can learn more about the age and composition of the Universe.”

“This is an exciting and completely new direction, and we look forward to applying our methods to future data sets to help constrain the Hubble constant, as well as other key cosmological quantities.”

As gravitational wave detectors become more sensitive in the coming years, the stochastic siren method could become the cornerstone of precision cosmology.

The gravitational wave background is expected to be detected within the next six years.

Until then, the method would constrain increasingly higher values ​​of the Hubble constant as the upper limits of the background improved, thus providing another probe of the Hubble voltage even without full detection.

“This should pave the way for applying this method in the future, as we continue to increase the sensitivity, better constrain the gravitational wave background and perhaps even detect it,” Cousins ​​said.

“By including this information, we hope to obtain better cosmological results and get closer to resolving the Hubble voltage.”

The team’s work will be published in the journal Physical Examination Letters.

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Bryce Cousins and others. 2026. Stochastic siren: background measurements of astrophysical gravitational waves of the Hubble constant. Phys. Reverend Lettin press; doi: 10.1103/4lzh-bm7y