Astrometry

Detecting exoplanets by measuring the precise positional wobble of a star on the sky.

Astrometry measures the tiny side-to-side motion of a star caused by the gravitational influence of an orbiting planet. Unlike radial velocity which measures motion toward and away from us, astrometry measures motion across the plane of the sky. This requires extraordinarily precise position measurements,the motion is typically measured in microarcseconds. The European Space Agency's Gaia mission is revolutionizing this technique by providing unprecedented positional accuracy for over a billion stars, and is expected to reveal thousands of new exoplanets through astrometric detection.