It will conduct a census of a billion stars in our galaxy, monitoring each of its target stars about 100 times over a five-year period, precisely charting their distances, movements, and changes in brightness. It is expected to discover hundreds of thousands of new celestial objects, such as extra-solar planets and failed stars called brown dwarfs. Within our own solar system, Gaia should also identify tens of thousands of asteroids.
Additional scientific benefits include detection and characterisation of tens of thousands of extra-solar planetary systems, a comprehensive survey of objects ranging from huge numbers of minor bodies in our solar system, through galaxies in the nearby Universe, to about 10 million galaxies and 500,000 distant quasars. It will also provide stringent new tests of general relativity.
The spacecraft will use the global astronomy concept successfully demonstrated on Hipparcos, also built by Astrium, which successfully mapped 100,000 stars in 1989. Gaia will be equipped with a latest-generation payload integrating the most sensitive telescope ever made. This cutting-edge technology draws on Astrium’s extensive experience particularly on silicon carbide (SiC) telescopes, used on the Herschel telescope and Aladin instrument as well as on three Earth observation satellites (Formosat, Theos and Alsat 2). Gaia’s measurement accuracy is so great that if it were on the Moon, it could measure the thumbnail of a person on Earth!
Gaia will be placed in orbit around the Sun, at a distance of 1.5 million kilometres further out than Earth, at the L2 Lagrangian point of the Sun–Earth system.