Gaia: the Galaxy in six (and more) dimensions

TL;DR

Gaia is a space mission launched in 2013 that maps the Milky Way in six dimensions by measuring positions, motions, and other properties of over two billion stars, significantly advancing astrophysics research.

Contribution

This paper provides an overview of Gaia's mission, instrumentation, data releases, and its impact on various astrophysical research areas, highlighting its comprehensive 6D galactic mapping.

Findings

High-precision astrometric measurements for over two billion sources.

First two Gaia data releases demonstrate significant scientific impact.

Gaia's multi-dimensional data enables diverse astrophysical studies.

Abstract

The ESA cornerstone mission Gaia was successfully launched in 2013, and is now scanning the sky to accurately measure the positions and motions of about two billion point-like sources of 3<V<20.5 mag, with the main goal of reconstructing the 6D phase space structure of the Milky Way. The typical uncertainties in the astrometry will be in the range 30-500 muas. The sky will be repeatedly scanned (70 times on average) for five years or more, adding the time dimension, and the Gaia data are complemented by mmag photometry in three broad bands, plus line-of-sight velocities from medium resolution spectroscopy for brighter stars. This impressive dataset is having a large impact on various areas of astrophysics, from solar system objects to distant quasars, from nearby stars to unresolved galaxies, from binaries and extrasolar planets to light bending experiments. This invited review paper presents an overview of the Gaia mission and describes why, to reach the goal performances in astrometry and to adequately map the Milky Way kinematics, Gaia was also equipped with state-of-the-art photometers and spectrographs, enabling us to explore much more than the 6D phase-space of positions and velocities. Scientific highlights of the first two Gaia data releases are briefly presented.