The Gaia spacecraft, designed to map the three-dimensional structure of our Galaxy, has provided a rich database of precision measurements enabling other types of science, most recently the discovery of exoplanets orbiting target stars. In a recent report by Aviad Panahi (Tel Aviv University) and collaborators, Gaia photometry was used for the first time to identify candidate exoplanet transit events, signaled by a dip in a star’s brightness as an orbiting planet passes along our line of sight and covers a part of the stellar disk.

Confirmation that the temporary dimming was the result of an orbiting exoplanet was obtained for two sources, with spectra from the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) on the Large Binocular Telescope. The data acquired over multiple epochs provide sensitive measures of the star’s radial velocity (i.e. speed of motion along our line of sight) which oscillates over time as the star is pulled by the gravity of an orbiting planet.

The LBT data enable estimation of the planets’ mass which in both cases resembles that of Jupiter. However, the newly discovered exoplanets orbit in close proximity to their parent stars, with periods of only 3 – 4 days, resulting in surface temperatures in excess of 1000 K. The discovery of these “hot jupiters” is an important demonstration of the potential for Gaia to extend the census of extrasolar planets.

The study findings are reported in Panahi et al. 2022, Astronomy & Astrophysics, 663, A101