LIGO and VIRGO’s detections of colliding black holes and neutron stars that create gravitational waves, or ripples in the fabric of space-time.

However, the mergers between supermassive black holes – billions of times the mass of the Sun — generate gravitational waves too long to register with these instruments. Now, after decades of careful observations, astronomers around the world using a different type of gravitational wave detection method have finally gathered enough data to measure what is essentially a gravitational wave background hum of the Universe, mostly from supermassive black holes spiraling toward collision. The newly detected gravitational waves are by far the most powerful ever measured, and they persist for years to decades. They carry roughly a million times as much energy as the one-off bursts of gravitational waves from black hole and neutron star mergers detected by LIGO and Virgo.

Links:
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background /Searching for the Nano-Hertz Stochastic Gravitational Wave Background with the Chinese Pulsar Timing Array Data Release I

A new view of the Universe – Clock-like precision of pulsars opens a new window in the gravitational wave spectrum

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Spektakuläre Entdeckung: Gigantische Gravitationswellen durchlaufen das Universum

After Decades of Observations, Astronomers have Finally Sensed the Pervasive Background Hum of Merging Supermassive Black Holes