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HIPPARCHUS (fl. 146–126 B.C.), Greek astronomer, was born at Nicaea in Bithynia early in the 2nd century B.C. He observed in the island of Rhodes probably from 161, certainly from 146 until about 126 B.C., and made the capital discovery of the precession of the equinoxes in 130 (see Astronomy: History). The outburst of a new star in 134 B.C. is stated by Pliny (Hist. nat. ii. 26) to have prompted the preparation of his catalogue of 1080 stars, substantially embodied in Ptolemy's Almagest. Hipparchus founded trigonometry, and compiled the first table of chords. Scientinc geography originated with his invention of the method of fixing terrestrial positions by circles of latitude and longitude. There can be little doubt that the fundamental part of his astronomical knowledge was derived from Chaldaea. None of his many works has survived except a Commentary on the Phaenomena of Aratus and Eudoxus, published by P. Victorius at Florence in 1567, and included by D. Petavius in his Uranologium (Paris, 1630). A new edition was published by Carolus Manitius (Leipzig, 1894).

See J. B. J. Delambre, Histoire de l'astronome ancienne, i. 173; P. Tannery, Recherches sur l'histoire de l'astr. ancienne, p. 130; A. Berry, Hist. of Astronomy, pp. 40–61; M. Marie, Hist. des sciences, i. 207; G. Cornewall Lewis, Astronomy of the Ancients, p. 207; R. Grant, Hist. of Phys. Astronomy, pp. 318, 437; F. Boll, Sphaera, p. 61 (Leipzig, 1903); R. Wolf, Geschichte der Astronomie, p. 45; J. F. Montucla, Hist. des mathématiques, t. i. p. 257; J. A. Schmidt, Variorum philosophicorum decas, cap. 1. (Jenae, 1691).  (A. M. C.)