Hipparcos

in full High Precision Parallax Collecting Satellite

Satellite launched by the European Space Agency that from 1989 to 1993 measured distances to more than 100,000 stars. Named after the 2nd-century-BC astronomer Hipparchus, who compiled the first known star catalog, the satellite was an orbiting telescope that could compute the position of a star to within 0.001 seconds of arc, or 20 times better than ground-based observations. These improved positions allowed much more accurate parallax determinations of stellar distances. Updated distances to Cepheid variables in particular refined the basis of the distance scale of the universe.

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