Gaia, A mission to map the stars and their movements.

A mission to map the stars and their movements

  • In development since 2007
  • Due to launch in 2011

The European Space Agency’s Gaia mission will examine the Milky Way in unprecedented 3-D detail.

The spacecraft will survey more than one billion stars to make the largest, most precise map of our Galaxy to date. Gaia will be scanning the sky continuously for five years. This will enable each object to be observed on average about 80 times. Gaia will log the position, brightness and colour of every celestial object of sufficient brightness that falls within its field of view. Gaia will be using the same principle of measurements that was successfully employed by the Hipparcos mission.

The repeated observations will allow astronomers to calculate positions, distances and velocities relative to the Sun for the objects that are observed. Any variations in brightness will also be followed and analysed. With this wealth of data, astronomers will be able to get a better understanding of the history and evolution of our Galaxy.

Gaia will also be able to detect large numbers of double stars throughout the Milky Way, as well as nearby planets that are the same size - or bigger - than Jupiter. It will do this by measuring small disturbances in the positions of stars caused by a planet's gravitational field. Scientists predict Gaia could find up to 50,000 planets during its five-year mission!

Mission facts

  • Gaia originally stood for Global Astrometric Interferometer for Astrophysics. As the project evolved, the double-interferometer concept was replaced with different instruments. However, the mission name remained even though it no longer uses an interferometer as part of its telescope design.

  • The measurement accuracy expected for Gaia will be about 10 to 100 times greater than what was achieved for the Hipparcos mission. The number of objects observed will be 10,000 times greater.

  • As part of its mission, Gaia is expected to detect tens of thousands of stars that failed to ignite. These are known as brown dwarves. The information gathered will help scientists understand the formation of stars.


Gaia will be equipped with two telescopes, projecting images onto a single integrated instrument. This will be able to record the position, brightness and colour of the objects under observation.

The spacecraft will be equipped with a ‘micro propulsion’ system, allowing fine adjustments to be made to its position.

UK involvement

The data processing for the mission involves pan-European collaboration, with significant leadership from the UK.

Within the UK, the Universities of Cambridge, Leicester, Edinburgh and Brunel are involved in data processing, along with the STFC Rutherford Appleton Laboratory and University College London’s Mullard Space Science Laboratory (MSSL).

A number of UK research groups and industrial partners such as MSSL and the Universities of Leicester and Cambridge have been involved in the design phase of the instruments on board Gaia.

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