Gravitational Waves with Relative Astrometry

Gravitational waves — ripples in spacetime caused by massive accelerating objects — have revolutionized our understanding of the Universe. While interferometric detectors, like LIGO and Virgo, have provided direct detections of these waves, new observational techniques are emerging to probe them in complementary ways. One such approach is relative astrometry, which uses precise measurements of the angular displacements of distant celestial objects to detect the passing of gravitational waves.

How It Works

When a gravitational wave passes through the Earth, it distorts the paths of photons coming to us from a background source, such as a star, and distorts the apparent position of the star. These distortions are time dependent, and so produces effects that can be measured by any telescope with sufficient angular resolution -- a dedicated astrometric mission, like Gaia, is not necessary! By tracking these minuscule shifts with high-precision astrometry from past and upcoming space missions, we can infer the presence of microhertz gravitational waves. These waves have frequencies too low to measure with interferometric detectors, and too high to measure with pulsar timing arrays. This method provides a ``free'' way of measuring microhertz gravitational waves with data we will soon have on-hand.

Applications and Implications

Relative astrometry opens new avenues for gravitational wave astrophysics by enabling:

• Detection of the mergers of supermassive black hole binaries.

• A complementary probe to pulsar timing arrays and space-based interferometers like LISA.

Recent Related Papers

A Fast Bayesian Method for Coherent Gravitational Wave Searches with Relative Astrometry

Led by USC GS Benjamin Zhang

Gravitational Wave Detection with Relative Astrometry using Roman's Galactic Bulge Time Domain Survey

Constraining the stochastic gravitational wave background with photometric surveys

Led by Caltech GS Yijun (Ali) Wang