Who are the Hipparcos and Tycho catalogues named for?
A. Hipparcos is an acronym for HIgh Precision PARallax COllecting Satellite. Appropriately the proununciation is also very close to Hipparchus, the name of a Greek astronomer who lived from 190 to 120 BC. By measuring the position of the Moon against the stars, Hipparchus was able to determine the Moon’s parallax and thus its distance from the Earth. He also made the first accurate star map which lead to the discovery, when compared with other data from his predecessors, that the Earth’s poles rotate in the sky, a phenomenon referred to as the precession of the equinoxes. The concept of using the data recorded by the star mappers for astrometric and photometric observations was conceived by Erik Høg, a Danish astronomer involved with the Hipparcos mission. It was fitting that the catalogue which resulted from the star mappers should then be named after Tycho Brahe, a 16th century Danish astronomer, who produced the first ‘modern’ star catalogue (1602).
