Billion star-mapper releases data

The Gaia observatory has released a second swathe of data as it assembles the most precise map of the sky. The European Space Agency telescope has now plotted the position and brightness of nearly 1.7 billion stars. It also has information on the distance, motion and colour of 1.3 billion of these objects. Leading Gaia scientist Prof Gerry Gilmore spoke with our correspondent Jonathan Amos.