Gaia maps more than 1 billion stars

BBC : The European Space Agency has released the first full-sky maps from its Gaia space telescope. Launched in 2013, Gaia is a follow-up to the Hipparcos satellite, which in the 1980s and 1990s cataloged the position, brightness, distance, and proper motion of 100 000 stars. In just three years Gaia has created a catalog 20 times as large, with position and brightness measurements for more than 1 billion stars in the Milky Way. The database also includes distance and proper motion for 2 million stars. By the end of its five-year mission, Gaia is expected to have collected a full set of measurements for nearly all the stars in the database. Beyond the four characteristics measured by Hipparcos, Gaia will also be measuring stars’ radial velocity—the motion of the stars toward or away from Earth as they sweep through the galaxy. The additional measurements will provide information about the structure and internal dynamics of the Milky Way, which should allow researchers to more accurately model the evolution of the galaxy.