Measuring a billion stars … for a billion euros! This is the bet of Gaia, the mission of surveying and 3D mapping that covers several percent of our galaxy. Launched in December 2013, the Gaia satellite has since ceased surveying space. On September 14th, the 450 or so scientists who interpret the data he transmitted delivered the first results of their deciphering work in the form of a catalog embryo which, eventually, will have to list about 1.2 billion stars . Among these researchers, astronomers from the University of Liège, trackers of quasars and binary stars. The Gaia mission is undoubtedly one of the most ambitious projects of the ESA. Launched from Kourou on December 19, 2013, this satellite is dedicated to astronomy, a branch of astronomy dedicated to measuring the position and motion of stars, allowing astronomers to show that stars are not Not fixed points in space but bodies in motion. ESA had launched a first measurement mission (Hipparcos) in 1989. It had resulted in the characterization of about 2 million stars of the Milky Way (the galaxy in which the Earth is located). This time, ESA has gone further, since it is about 1% of our galaxy that has been screened, or nearly 1.2 billion stars. “Gaia’s goal,” explains Eric Gosset, one of the University of Liège’s astronomers involved in the mission, is to establish the movement of these stars on the celestial vault and their position with unprecedented accuracy, to measure their distance In relation to us and for some, the speed at which they move away (or come closer!) From us. ” On September 14, a first burst of data accumulated in the mission computers and processed according to the automatic procedures under development, will be disclosed and made available to researchers around the world. It will also be the occasion to publish the first articles written by the members of the consortium. “But we must not rejoice too quickly, tempers Eric Gosset. It is still very fragmentary; The purpose of this data release is that many researchers other than the members of the consortium seize this data and start working on it. ”