Hipparcos, the New Reduction of the Raw Data

Thepublication of theHipparcos andTycho Catalogues in 1997 transformed astrometry, and as a consequence astronomers’ perception of astrometry. What had before often been regarded as a somewhat quaint specialty of limited re- vance to modern astrophysics, was suddenly seen to produce a wealth of data of immediate practical use. The ready availability of many thousand precise trigonometric stellar distances and the access to an accurate and dense - tical reference frame have changed the way a...