This 21st volume in the series contains 15 invited reviews and highlight contributions presented during the 2008 International Scientific Conference of the German Astronomical Society on the topic of "New Challenges to European Astronomy", held in Vienna, Austria. The papers discuss a wide range of hot topics, including cosmology, high-energy astrophysics, astroparticle physics gravitational waves, extragalactic and stellar astronomy -- together representing the roadmap for modern astrophysical research.
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