ESA’s Gaia satellite is a €740-million mission to map a billion stars in our galaxy. By observing repeatedly with unprecedented astrometric precision it is measuring the parallaxes, and thus the distances, of hundreds of millions of stars, and so mapping out the 3-D structure of our galaxy.

Gaia can detect exoplanets in two ways, first by astrometry (measuring the position of a star), so detecting the wobble in the star’s location caused by an orbiting massive planet, and secondly by the transit method, detecting the dip in the light of a star caused by a transiting planet.

The Gaia team have just announced the first detections of exoplanet transits, by looking at the accumulated Gaia data on two already-known WASP planets.

The plot shows a year’s worth of Gaia data of the star WASP-19, folded on the 0.79-day orbital period of the planet WASP-19b (the three different panels are the star’s magnitude in three different colours). The coverage is sparse — it is designed for astrometric measurements, not for recording lightcurves — but one observation was made in-transit, demonstrating that Gaia can indeed detect exoplanet transits.

The ESA/Gaia team have also looked at the data on WASP-98, and again detect the transit of WASP-98b.