astrometry

Fusing astrometry and direct imaging not only opens the door to finding more targets; it also eliminates some of this guesswork by revealing each newfound planet’s orbit and mass, along with its atmosphere.

A related technique, astrometry, could do much the same thing, pinpointing planetary masses by measuring how each world’s gravitational influence slightly shifts its star’s position in the plane of the sky.

"We show that the existence of the planet can be ascertained, and its true mass can be determined with high accuracy, by combining Gaia astrometry and radial velocities."

Measuring these shifts, or parallaxes, lets astronomers calculate the stars’ actual positions and movements through the galaxy with great precision, a field of study called astrometry that Gaia and its predecessor Hipparcos have revitalized.

The astrometry data collected by Gaia will augment scientific observations made by powerful ground-based telescopes.