The »ultimate rave« is coming to an end. Of course, in this case it is not a techno party, but the so-called RAdial Velocity Experiment, the largest spectroscopic survey of the southern hemisphere. The international RAVE collaboration has now presented the results in its sixth and final data publication in the specialist journal “The Astronomical Journal”. The project has successfully measured the temperatures, compositions, velocities and distances for many different types of stars, thus providing a complete picture of their motion and the chemical composition of our Milky Way.

To do this, RAVE observed the sky on almost every clear night between 2003 and 2013 with the 1.2-meter Schmidt telescope at the Anglo-Australian Observatory in Siding Spring, Australia. In total, RAVE recorded more than half a million spectra of around 450,000 Milky Way stars, which are approximately in a volume with a diameter of 15,000 light years. Before that, the largest spectroscopic survey had only included about 14,000 objects.


© AIP / K. Riebe, RAVE collaboration; Milky Way picture (background): R. Hurt (SSC); NASA / JPL-Caltech (detail)

Stars observed with RAVE | With RAVE, astronomers observed almost half a million stars in the Milky Way. The sun is at the center of the coordinate system. The colors represent radial speeds: moving stars are shown in red, approaching stars in blue.

A special fiber optic was used at RAVE, with which the spectra of up to 150 stars could be recorded at the same time. Spectroscopy breaks down the light into its individual color components. The spectrum of a star can be used to determine a number of properties, including its radial velocity or chemical composition.

With RAVE it was possible to show, among other things, that the Milky Way disk is constructed asymmetrically. The data could confirm that dark matter dominates the mass of our galaxy. In addition, the scientists identified star currents in the sun’s surroundings, the remains of torn-apart older dwarf galaxies that in the past have merged with our Milky Way. And the chemical composition of the observed stars provided information about the star formation and the development of the Milky Way.