Astronomers Just Found a New Way to Hear the Universe’s Gravitational Symphony—Using Quasars

Astrophysicist pioneers method to measure cosmic ripples through quasar movements

Scientists have developed a promising new approach to detect the universe’s gravitational waves – ripples in spacetime that wash over our planet constantly but remain largely invisible to conventional observation methods. This innovative technique could unlock deeper understanding of how supermassive black holes interact and potentially transform our knowledge of fundamental physics.

University of Colorado Boulder astrophysicist Jeremy Darling has published research in The Astrophysical Journal Letters that examines gravitational waves from a unique perspective – by precisely tracking the apparent motion of distant celestial objects called quasars. His approach offers a complementary method to recent breakthrough measurements and could eventually provide a more complete picture of cosmic gravitational phenomena.

“There is a lot we can learn from getting these precise measurements of gravitational waves,” explains Darling, professor in the Department of Astrophysical and Planetary Sciences. “Different flavors of gravity could lead to lots of different kinds of gravitational waves.”

Capturing the Universe’s Hidden Ripples

Think of Earth as a buoy bobbing in a stormy ocean of spacetime. Throughout cosmic history, countless supermassive black holes have engaged in gravitational dances, spiraling toward each other until they collide in cataclysmic events that generate ripples spreading throughout the universe.

Last year, scientists from the NANOGrav collaboration achieved a breakthrough by measuring this gravitational wave background through pulsar observations. However, these measurements only captured how waves stretch and squeeze spacetime in one dimension – similar to waves flowing directly toward and away from a shoreline.

Darling’s research extends this understanding by examining how gravitational waves move in additional dimensions relative to Earth – the side-to-side and up-and-down motions that create a more complete picture of these cosmic ripples.

Key Findings from the Gravitational Wave Research

• The study analyzed over 1 million quasars observed by the European Space Agency’s Gaia satellite
• Researchers examined 2,104,609,881 quasar pairs to detect correlated motion patterns
• The technique measured spatial correlations down to ±0.005 micro-arcseconds squared per year squared
• The study established an upper limit on gravitational wave energy density at 0.0096
• This represents the first time optical wavelength astrometry has surpassed radio-frequency measurements

“Gravitational waves operate in three dimensions,” Darling notes. “They stretch and squeeze spacetime along our line of sight, but they also cause objects to appear to move back and forth in the sky.”

Observing the Unobservable

The research focuses on quasars – exceptionally bright objects powered by supermassive black holes at the centers of distant galaxies. Although quasars are millions of light-years away, the light they emit gets subtly deflected by passing gravitational waves, creating an apparent “wiggling” motion when viewed from Earth.

Detecting this motion requires extraordinary precision. The measurements needed are about 10 times more precise than what it would take to watch a human fingernail growing on the moon from Earth. Additionally, researchers must account for Earth’s own complex motion through space to isolate the gravitational wave signals.

“If you lived for millions of years, and you could actually observe these incredibly tiny motions, you’d see these quasars wiggling back and forth,” Darling said.

While current data isn’t yet detailed enough to conclusively prove gravitational waves are causing quasar wiggling, the study establishes important methodological groundwork and sets increasingly stringent constraints on gravitational wave energy levels.

Future Prospects for Cosmic Detection

Are we close to detecting these elusive signals? The Gaia satellite team plans to release 5.5 additional years of quasar observations in 2026, providing astronomers with a substantially larger dataset that may finally reveal clear evidence of gravitational wave effects on quasar positions.

“If we can see millions of quasars, then maybe we can find these signals buried in that very large dataset,” said Darling.

The implications of this research extend beyond pure astronomy. Understanding gravitational waves could help scientists track galaxy evolution and test fundamental assumptions about gravity itself. It represents a significant step toward developing a more complete toolkit for observing some of the most powerful and mysterious phenomena in our universe.