Gaia and the dynamics of the Galaxy
  Gaia is an ambitious ESA space mission which will provide photometric and astrometric measurements with the accuracies needed to produce a kinematic census of almost one billion stars in our Galaxy. These data will revolutionize our understanding of the dynamics of the Milky Way, and our knowledge of its detailed gravitational potential and mass distribution, including the putative dark matter component and the non-axisymmetric features such as spiral arms. The Gaia mission will help to answer various currently unsettled questions by using kinematic information on both disk and halo stellar populations. Among many others: what does the rotation curve of the outer Galaxy look like? How far from axisymmetry and equilibrium is the Galaxy? What are the respective roles of hierarchical formation and secular evolution in shaping the Galaxy and its various components? Are the properties of the Galaxy in accordance with expectations from the standard model of cosmology? 
Benoit Famaey
astro-ph.GA astro-ph.CO