The European Space Agency's billion-star surveyor, Gaia, has been launched into space on a Soyuz rocket.
Gaia is set to embark on a five-year mission to map the stars in 3D with unprecedented precision and discover thousands of previously unknown objects, including exploding stars, planets orbiting other suns, and nearby asteroids.
British scientists and engineers have played key roles in the design and construction of the two-tonne space telescope, which blasted off from Europe's Spaceport in Kourou, French Guiana.
Scientists also hope Gaia will yield clues about mysterious Dark Matter and Dark Energy.
A satellite being launched into orbit around the sun today was partly built in Stevenage. The Gaia satellite will be mapping a billion stars and all the data will be sent to earth via a computer built at Astrium. The company also made the satellite's propulsion system.