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R.P. Olling (USRA & University of Maryland at College Park)
Future astrometric missions such as SIM & GAIA will revolutionize our understanding of the Milky Way and will firmly establish our home galaxy as a benchmark for extra-galactic research. SIM & GAIA will not only provide very accurate stellar distances and hence luminosities. For the subset of eclipsing spectroscopic binaries, all fundamental parameters can be determined: mass from astrometry & spectroscopy, luminosity from distance and apparent magnitude, and radius from detailed light-curve analysis. With all fundamental stellar parameters precisely known, the ages of individual components of the binary can be determined fairly accurately.
Currently, the limitation for such analyses is the relatively poorly determined absolute luminosity (large parallax errors). GAIA will provide astrometry at the 15 \muarcsec level for stars brighter than 15, or with accuracies better than 1% for an estimated 50 million stars closer than 666 pc. Since roughly 0.9% of stars is an eclipsing binary, plenty of targets (450,000) in the GAIA sample are available for age determination. This large sample of stars with accurately determined ages forms the fossil record of the formation of the Milky Way and will reveal the assembly history of the Galaxy (the star-formation history), the evolution of the metal abundance, the Helium abundance, and the number of major and minor mergers. These parameters can be tracked in all three components of the Milky Way: thin- and thick disk and stellar halo. As such, GAIA-data will enable "cosmology in our own back yard," i.e., the detailed understanding of the process of galaxy formation.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.