Second only to black holes, neutron stars – incredibly dense star remnants – are the densest objects in the universe. When neutron stars collide, they create ripples in the fabric of space and time in a way that we can detect on Earth.

We can then use these ripples to measure one of the universe’s most fundamental but elusive properties – how fast it is expanding. This is called the Hubble constant, and scientists have pursued and debated it for decades.

In recent years, the debate has intensified. Scientists using different techniques keep arriving at divergent answers. This growing problem, known as the “Hubble tension”, has become one of the biggest challenges in modern cosmology.

In a study published in The Astrophysical Journal today, we have developed a new approach in an attempt to pin down the Hubble constant. To do so, we re-examined gravitational waves caused by a dramatic collision of two neutron stars.

We believe our results provide the most precise measurement of the Hubble constant to date using the gravitational wave method.

Why do we need the Hubble constant?

Knowing how fast the universe is expanding is fundamental for astronomers. It sets the cosmic scale for our measurements, enabling us to determine the true distance and size of astrophysical objects. Even more profoundly, it tells us about how the universe began and how it could end.

Given its importance, we’ve been trying to measure the Hubble........

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