Imagine Earth as a small boat on a quiet sea, gently rocked by waves you can’t see. Those “waves” are actually ripples in space and time called gravitational waves, created when massive black holes crash into each other. A team at the University of Colorado Boulder has a new idea for measuring these waves by watching how they make distant quasars, superbright galactic cores, appear to move in the sky.
Gravitational waves usually stretch and squeeze space in one direction, like pulling and pushing on a slinky. Scientists first detected these waves flowing toward and away from us by watching how pulsars (spinning dead stars) timed their signals. But Earth also drifts through space, and those measurements only show one slice of the story.
“There is a lot we can learn from getting these precise measurements of gravitational waves,” said Jeremy Darling, professor in the Department of Astrophysical and Planetary Sciences. “Different flavors of gravity could lead to lots of different kinds of gravitational waves.”
Darling’s method looks for side-to-side motion. As a gravitational wave passes, it bends light from a quasar just a tiny bit, making the quasar seem to wobble back and forth. It’s like seeing a distant lighthouse flicker because the air above the sea is shimmering.
Watching these wobbles is tough. The shifts are so small you’d need to spot a fingernail growing on the moon to see them. Plus, our own planet is zipping around the sun at about 67,000 miles per hour, and the sun is racing through the galaxy at 850,000 miles per hour. Sorting out all that motion to find the ripples is a huge puzzle.
To start, Darling used data from the European Space Agency’s Gaia satellite, which since 2013 has mapped over a million quasars. By pairing up quasars and tracking how their positions change relative to each other, he hopes to pick out the gravitational-wave signal.
So far, the results aren’t conclusive. But they show that this three-dimensional approach could fill in gaps in our understanding of gravity and galaxy collisions. And in 2026, Gaia will release more than five more years of quasar data, giving Darling and his team an even bigger set of observations to work with.
“If we can see millions of quasars, then maybe we can find these signals buried in that very large dataset,” he said. With more data and this new technique, we could soon get a clearer picture of how gravitational waves shape our universe.
The study has been published in The Astrophysical Journal Letters.
Source: University of Colardo at Boulder.
