Cassini, Gian Domenico


Cassini, Gian Domenico
born June 8, 1625, Perinaldo, Republic of Genoa
died Sept. 14, 1712, Paris, France

Italian-born French astronomer.

His early studies were mainly observations of the Sun, but, after obtaining more powerful telescopes, he turned his attention to the planets. He calculated Jupiter's and Mars's rotational periods and compiled a table of the positions of Jupiter's satellites. His observations of the Moon (1671–79) led to his compiling a large map. In 1683, after a study of the zodiacal light, he concluded it was of cosmic origin. He discovered four of Saturn's moons: Iapetus (1671), Rhea (1672), Tethys (1684), and Dione (1684). The dark gap between two of Saturn's main rings (Cassini's division) is named for him.

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▪ French astronomer
(Italian),French  Jean-dominique Cassini  
born June 8, 1625, Perinaldo, Republic of Genoa
died Sept. 14, 1712, Paris

      Italian-born French astronomer who, among others, discovered Cassini's division, the dark gap between the rings A and B of Saturn; he also discovered four of Saturn's moons. In addition, he was the first to record observations of the zodiacal light.

      Cassini's early studies were principally observations of the Sun, but after he obtained more powerful telescopes, he turned his attention to the planets. Observing the shadows of Jupiter's satellites as they passed between that planet and the Sun, he was able to measure Jupiter's rotational period. In 1666, after similar observations of Mars, he found the value of 24 hours 40 minutes for Mars's rotational period; it is now given as 24 hours 37 minutes 22.6 seconds. Two years later he compiled a table of the positions of Jupiter's satellites that was used in 1675 by the Danish astronomer Ole Rømer (Rømer, Ole) to establish that the speed of light is finite. In addition, he wrote several memoirs on flood control, and he experimented extensively in applied hydraulics.

      Hearing of Cassini's discoveries and work, King Louis XIV of France invited him to Paris in 1669 to join the recently formed Académie Royale des Sciences. Cassini assumed the directorship of the Observatoire de Paris after it was completed in 1671, and two years later he became a French citizen.

      Continuing the studies begun in Italy, Cassini discovered the Saturnian satellites Iapetus (1671), Rhea (1672), Tethys (1684), and Dione (1684). Between 1671 and 1679 he made observations of the Moon, compiling a large map, which he presented to the Académie. In 1675 he discovered Cassini's division and expressed the opinion that Saturn's rings were swarms of tiny moonlets too small to be seen individually, an opinion that has been substantiated. In 1683, after a careful study of the zodiacal light, he concluded that it was of cosmic origin and not a meteorological phenomenon, as some proposed.

      In 1683 Cassini began the measurement of the arc of the meridian (longitude line) through Paris. From the results, he concluded that the Earth is somewhat elongated (it is actually somewhat flattened at the poles). A traditionalist, he accepted the solar theory of Nicolaus Copernicus within limits, but he rejected the theory of Johannes Kepler that planets travel in ellipses and proposed that their paths were certain curved ovals, which came to be known as Cassinians, or ovals of Cassini. Although Cassini resisted new theories and ideas, his discoveries and observations unquestionably place him among the most important astronomers of the 17th and 18th centuries.

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Universalium. 2010.

Look at other dictionaries:

  • Cassini, Gian Domenico — (8 jun. 1625, Perinaldo, República de Génova–14 sep. 1712, París, Francia). Astrónomo francés de origen italiano. Sus primeros estudios fueron principalmente observaciones del Sol. Sin embargo, después de obtener telescopios más potentes, volvió… …   Enciclopedia Universal

  • Cassini, Gian Domenico — (1625 AD 1712 AD)    Italian born astronomer who discovered four of Saturn s satellites, and noticed a dark division in the rings which was named for him, the Cassini Division …   The writer's dictionary of science fiction, fantasy, horror and mythology

  • Cassini-Huygens — ▪ space mission  U.S. European space mission to Saturn, launched on Oct. 15, 1997. The mission consisted of the U.S. National Aeronautics and Space Administration s (NASA) Cassini orbiter, which was the first space probe to orbit Saturn, and the… …   Universalium

  • Domenico — (as used in expressions) Domenico Zampieri Beccafumi Domenico Domenico di Giacomo di Pace Cassini Gian Domenico Cimarosa Domenico Domenico Veneziano Donizetti Domenico Gaetano Maria Ghirlandaio Domenico Domenico di Tommaso Bigordi Antonio… …   Universalium

  • Domenico — (as used in expressions) Beccafumi, Domenico Domenico di Giacomo di Pace Cassini, Gian Domenico Cimarosa, Domenico Domenico Zampieri Domenico Veneziano Donizetti, (Domenico) Gaetano (Maria) Ghirlandaio, Domenico Domenico di Tommaso Bigordi… …   Enciclopedia Universal

  • Gian — (as used in expressions) Bernini Gian Lorenzo Cassini Gian Domenico Menotti Gian Carlo Poggio Bracciolini Gian Francesco Visconti Gian Galeazzo * * * …   Universalium

  • Gian — (as used in expressions) Bernini, Gian Lorenzo Cassini, Gian Domenico Menotti, Gian Carlo Poggio Bracciolini, Gian Francesco Visconti, Gian Galeazzo …   Enciclopedia Universal

  • Cassini Division —    The spaces between the rings of Saturn. See Cassini, Gian Domenico …   The writer's dictionary of science fiction, fantasy, horror and mythology

  • Cassini, Jacques — ▪ French astronomer born Feb. 18, 1677, Paris, France died April 15/16, 1756, Thury       French astronomer who compiled the first tables of the orbital motions of Saturn s satellites.       He succeeded his father, the astronomer Gian Domenico… …   Universalium

  • Cassini's laws — ▪ astronomy  three empirical rules that accurately describe the rotation of the Moon, formulated in 1693 by Gian Domenico Cassini. They are: (1) the Moon rotates uniformly about its own axis once in the same time that it takes to revolve around… …   Universalium


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