Space Astrometry with Gaia: Advances in Understanding our Galaxy

Abstract: Gaia is a satellite mission of the European Space Agency which is creating a catalogue of extremely accurate positions, distances and space motions of two billion stars in our Galaxy, along with more than one hundred thousand solar system asteroids, and several million distant quasars, all on the same extragalactic reference system. Complementary information on each object's multi-epoch photometry and spectra provides a vast and unprecedented data base of (model-dependent) fundamental physical quantities, such as each star's mass, age, and chemical composition. I outline the field's historical context, and explain the key principles involved in these space measurements. This is followed by a broad review of the many areas of solar system science, stellar structure and evolution, and topics in Galactic structure, evolution, and dynamics, that are being derived from these data.