Abstract

Astrometry from space has unique advantages over ground-based observations: the all-sky coverage, relatively stable and temperature- and gravity-invariant operating environment delivers precision, accuracy and sample volume several orders of magnitude greater than ground-based results. Even more importantly, absolute astrometry is possible. The European Space Agency Cornerstone mission Gaia is delivering that promise. Gaia provides 5-D phase space measurements, 3 spatial coordinates and two space motions in the plane of the sky, for a representative sample of the Milky Way’s stellar populations (over 2e9 stars, being ~1% of the stars over 50% of the volume). Full 6-D phase space data is delivered from line-of-sight (radial) velocities for the 300 million brightest stars. These data make substantial contributions to astrophysics and fundamental physics on scales from the Solar System to cosmology. A few example results will be given.