Gaia-4b is a planet orbiting the star called Gaia-4, around 244 light-years away. Gaia-4b is about twelve times more massive than Jupiter. With an orbital period of 570 days, it is a relatively cold gas giant planet. This artist impression visualises a portion of the orbital motion as determined by Gaia’s astrometric data. The star and planet are not to scale. Image credit: ESA/Gaia/DPAC/M. Marcussen
Discovering Exoplanets with Gaia
Gaia is a spacecraft dedicated to making ultra-precise measurements of the positions and on-sky motions of billions of stars. The technical name for this measurement is astrometry, and the astrometric data collected by Gaia is invaluable for stellar science, orbital dynamics of the Milky Way Galaxy, and studies of exoplanets. While it just completed its full data collection mission, Gaia is just getting started in finding planets, with its first astrometric exoplanet candidates being uncovered recently.
Astrometry can be used to discover exoplanets through the subtle wobbles of a star under the gravitational influence of one or more orbiting planets. While the measurement is somewhat different, the physics behind this technique are identical to those used for the radial velocity technique employed by NEID. While astronomers have attempted to discover exoplanets using astrometry for decades, only Gaia currently has the measurement precision and sample size to do so in great numbers.
However, the astrometric exoplanet detections from Gaia remain candidates until they have been confirmed with other techniques such as with the radial velocity method. Today, we announced the discovery of Gaia-4b and Gaia-5b, which were initially detected by Gaia and confirmed with a collection of radial velocity spectrometers, including NEID. These planets represent the first confirmed exoplanets discovered by Gaia astrometry!
The full story of this announcement is described in a post on our blog for NEID’s sister spectrometer, the Habitable-zone Planet Finder. We encourage you to go there for all the details! The technical aspects of the project are provided in an article published in The Astrophysical Journal, led by NEID Team member Gudmundur Stefansson.