ESA’s Gaia mission has one main goal, to map the Milky way more extensively and with greater precision than any other mission to date. 
Using astrometry, the science of measuring the distance and motion of stars, Gaia will map a billion stars over a 5 year period to produce a comprehensive catalogue of measurements that will impact on most areas of astrophysics.

Pic du Midi, timelapse of stars : credit Romain Montagut