The positions of more than one billion stars in our Galaxy have been mapped with unprecedented precision by the European Space Agency's Gaia satellite (artist's impression pictured).
The craft launched in 2013 with the aim of making the most detailed ever 3D map of a portion of the Milky Way — including distances to stars from Earth, which are difficult to measure. Lennart Lindegren at Lund University in Sweden and his colleagues processed the first version of the data set, whose uncertainties are one-third of the size of those from the satellite's predecessor, Hipparcos. The catalogue currently includes some two million measurements of parallax — a star's apparent shift in position in the sky as Earth orbits the Sun — which allows scientists to determine the star's distance from Earth.
The catalogue should eventually allow researchers to improve on estimates of the locations of most distant galaxies and the expansion of the Universe, which are measured relative to distances between nearer objects.