Clues to how galaxies formed in the early Universe lie right under our nose - in our own Galaxy. The Galaxy formed by the accretion of infalling satellite galaxies, a number of astronomers think. Theoretical models of the formation of galaxies predict such a scenario.

But not all astronomers are convinced yet and the topic is still controversial. Now scientists from eleven countries have launched an ambitious project to reconstruct our Galaxy's history by gathering key components of motion and chemical compositions for its apparently brightest 50 million stars. RAVE (RAdial Velocity Experiment) is an all-sky stellar spectroscopy survey just started on the 1.2-m UK Schmidt telescope in eastern Australia. Projects such as Hipparcos and Tycho have accurately measured the positions and proper motions - movement across the sky - of more than 2.5 million stars. But to get a complete picture of stellar motions, and thus to enable astronomers to reconstruct the structure and formation history of our Galaxy, they also need radial velocities - the movement of stars towards or away from the observer. And before RAVE began only about 20,000 stellar radial velocities were in the archives.

RAVE will be able to achieve velocities accurate to within 2 kms-1 - about 1% of the speed at which stars typically move in the Galaxy. "With this accuracy and this number of radial velocities we will be able to identify dozens, perhaps hundreds, of streams of stars in the solar vicinity.