This method consists of making precise measurements to a star's position over time to detect a wobble. Until recently telescopes did not have the resolution needed to detect this type of motion. Astrometry will be more sensitive to planets with large orbits, which is an advantage it has over some of the other methods. The Gaia mission, which launched in 2013, will advance the field of astrometry much further. While 4 exoplanets have been detected using the Astrometry method as of November 2018 none of these discoveries have been confirmed by other methods, however the field is promising.
Artist's impression of the Gaia satellite. Image credit: ESA