Hipparchus


Hipparchus
(c. 170 bc–c. 120 bc) Greek astronomer and geographer
Born at Nicaea, which is now in Turkey, Hipparchus (hi-par -kus) worked in Rhodes, where he built an observatory, and in Alexandria. None of his works has survived but many of them were recorded by Ptolemy. In 134 bc he observed a new star in the constellation of Scorpio. This led him to construct a catalog of about 850 stars. By comparing the position of the stars of his day with those given 150 years earlier he found that Spica, which was then 6° from the autumn equinox, had previously been 8°. He used this observation to deduce not the movement of Spica but the east to west precession (motion) of the equinoctial point. He calculated the rate of the precession as about 45 seconds of arc a year – a value close to the 50.27 seconds now accepted. He also introduced the practice of dividing the stars into different classes of magnitude based on their apparent brightness. The brightest stars he classed as first magnitude and those just visible to the naked eye he classed as sixth magnitude.
As a theorist Hipparchus worked on the orbits of the Sun and Moon. He established more accurate lengths of both the year and the month and was able to produce more accurate eclipse predictions. One of his lasting achievements was the construction of a table of chords, which virtually began the discipline of trigonometry. The concept of a sine had not yet been developed. Instead, Hipparchus calculated the ratio of the chord to the diameter of its own circle, which was divided into 120 parts. Thus if a chord produced by an angle of 60° is half the length of the radius, it would have, for Hipparchus, 60 parts. He much improved the geography of Eratosthenes, fixing the parallels astronomically.

Scientists. . 2011.

Look at other dictionaries:

  • Hipparchus — (Greek polytonic|Ἵππαρχος; ca. 190 BC ndash; ca. 120 BC) was a Greek astronomer, geographer, and mathematician of the Hellenistic period.Hipparchus was born in Nicaea (now Iznik, Turkey), and probably died on the island of Rhodes. He is known to… …   Wikipedia

  • Hipparchus — puede hacer referencia a: Hipparchus, astrónomo griego también conocido como Hiparco de Nicea. Hipparchus, cráter del planeta Marte. Hipparchus, cráter de La Luna. Esta página de desambiguación cataloga artículos relacionados con el mismo título …   Wikipedia Español

  • Hippárchus — Hippárchus, Sohn des Pisistratus, mit seinem Bruder Hippias (s.d.) Herrscher von Athen, 514 v. Chr. am Fest der Panathenäen aus Privatrache von Harmodius und Aristogiton ermordet …   Kleines Konversations-Lexikon

  • Hippárchus [2] — Hippárchus, aus Nicäa, Gründer der wissenschaftlichen Astronomie, lebte um 160 125 v. Chr. in Alexandria, bestimmte zuerst die Jahreslänge sowie die Entfernungen und Größe von Sonne und Mond genauer, berechnete die ersten Sonnen und Mondtafeln,… …   Kleines Konversations-Lexikon

  • Hipparchus [1] — Hipparchus, Sohn des Pisistratus, mit seinem Bruder Hippias Beherrscher Athens, wurde 514 v. Chr. ermordet, s. Athen Bd. I. S. 307 u. Harmodius …   Herders Conversations-Lexikon

  • Hipparchus [2] — Hipparchus, alexandrin. Astronom, einer der verdientesten des Alterthums, geb. zu Nicäa in Bithynien, lebte um 160–125 v. Chr. Von ihm sind die ersten Sonnen u. Mondtafeln, die erste zusammenhängende Theorie über die Mondbewegung; auch die… …   Herders Conversations-Lexikon

  • Hipparchus — [hi pär′kəs] 2d cent. B.C.; Gr. astronomer …   English World dictionary

  • Hipparchus — /hi pahr keuhs/, n. 1. died 514 B.C., tyrant of Athens 527 514. 2. c190 c125 B.C., Greek astronomer. * * * or Hipparchos born , Nicaea, Bithynia died after 127 BC, Rhodes? Greek astronomer and mathematician. He discovered the precession of the… …   Universalium

  • Hipparchus, S. — S. Hipparchus et 6 Soc. MM. (9. Dec.) Vom Griech. ο τππος = das Pferd, und ἂρχειν = herrschen; also Bferdebeherrscher, oder besser Oberst (ἀρχός) der Reiterei (cἱππος etc. – Der hl. Martyrer Hipparchus und sein Freund Philotheus lebten zur Zeit… …   Vollständiges Heiligen-Lexikon

  • HIPPARCHUS — I. HIPPARCHUS Dux Atheniensium, coniurans contra Heraclidem Demetrii praesidem, Athenas frenantem; occisus ab eodem detectâ per Hieroclem coniuratione. Polyaen. l. 5. II. HIPPARCHUS Nicaeus Astrologus, scripsit de Arati Phaenomenis, de stellis… …   Hofmann J. Lexicon universale


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.