The branch of astronomy that involves precise measurement of stellar positions and motions in the sky. This field provides fundamental data for determining distances, proper motions, and the three-dimensional structure of our galaxy.
From Greek 'astron' meaning star and 'metron' meaning measure. The field traces back to ancient astronomers who catalogued star positions, but modern astrometry began with Tycho Brahe's precise observations and reached new heights with space missions like Hipparcos and Gaia.
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