: Earlier today the European Space Agency’s Gaia
space observatory launched successfully on a Soyuz rocket from French Guiana. The craft will travel some 1.5 million km to take up a position at Lagrange point L2
, where, in Earth's constant shadow, it will rotate at regular intervals and its two telescopes will sweep the sky. The images gathered by its 1-billion-pixel camera will be used to create a three-dimensional map of some one hundred billion stars in the Milky Way galaxy. By studying the stars’ positions and motions, astronomers hope to learn more about our galaxy’s origin, composition, and evolution. The craft is the successor to an earlier ESA mission, Hipparcos
, the first space experiment devoted to precision astrometry, which was launched in 1989 and collected data through 1993.