The Gaia catalogue is released in stages that will contain increasing amounts of information; the early releases also miss some stars, especially fainter stars located in dense star fields and members of close binary pairs. The first data release, Gaia DR1, based on 14 months of observations made through September 2015, took place on 14 September 2016 and is described in a series of articles published in "Astronomy and Astrophysics". The data release includes "positions and … magnitudes for 1.1 billion stars using only "Gaia" data; positions, parallaxes and proper motions for more than 2 million stars" based on a combination of "Gaia" and Tycho-2 data for those objects in both catalogues; "light curves and characteristics for about 3000 variable stars; and positions and magnitudes for more than 2000 … extragalactic sources used to define the celestial reference frame". Data from this DR1 release can be accessed at the "Gaia" archive, as well as through astronomical data centers such as CDS.