Gaia charted the Milky Way in three dimensions by surveying nearly two billion objects
Background
Gaia is a global space astrometry mission of the European Space Agency.
It built the largest, most precise three-dimensional map of our Galaxy by surveying nearly two billion objects.
Gaia monitored each of its target stars about 14 times per year, charting their positions, distances, movements, and changes in brightness.
It measured the positions of objects down to magnitude 20, and for objects brighter than magnitude 15 it reached an accuracy of 24 microarcseconds.
Gaia also studied more than 1 million distant quasars and provided stringent new tests of the General Theory of Relativity of Albert Einstein.
The spacecraft carried two optical telescopes working with three science instruments, and the status of the mission is now given as Post-operations.
In plain words
Astrometry — The branch of astronomy that measures the positions and motions of stars and other bodies.
Magnitude — A scale of brightness in which a larger number means a fainter object.
Microarcsecond — A millionth of an arcsecond, the unit in which very small angles on the sky are measured.
Quasar — An extremely bright and very distant object powered by matter falling into a massive black hole.