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Chronology of Solar System Discovery

##### by Bill Arnett

## Prior to 1600

From the dawn of history until the beginning of the 17th century the known universe consisted of only 8 bodies:

        Sun
        Mercury
        Venus
        Earth
        Moon
        Mars
        Jupiter
        Saturn

plus the "fixed" stars. In Europe, the prevailing view was the Ptolemaic system with the Earth at the center and the other bodies revolving around it.

## The 17th Century

In 1610 Galileo Galilei first turned a telescope on the heavens and the universe exploded. By the end of the 17th century, 9 new bodies had been discovered and Copernicus's heliocentric theory was widely accepted. The total number of known bodies had more than doubled to 17:

        Callisto   1610   Galileo Galilei
        Europa     1610   Galileo Galilei
        Ganymede   1610   Galileo Galilei
        Io         1610   Galileo Galilei
        Titan      1655   Christiaan Huygens
        Iapetus    1671   Giovanni Domenico Cassini
        Rhea       1672   Giovanni Domenico Cassini
        Dione      1684   Giovanni Domenico Cassini
        Tethys     1684   Giovanni Domenico Cassini

## The 18th Century

Only 5 new bodies (not counting comets) were discovered in the 18th century (all by William Herschel) bringing the total to 22:

        Uranus     1781   William Herschel
        Oberon     1787   William Herschel
        Titania    1787   William Herschel
        Enceladus  1789   William Herschel
        Mimas      1789   William Herschel

## The 19th Century

The number of bodies in the solar system increased dramatically in the 19th century with the discovery of the asteroids (464 of which were known at by 1899) but only 9 more "major" bodies were discovered. The number of major bodies rose to 31 (almost doubling the 17th century total):

        Neptune    1846   Johann Gotfried Galle, Urbain Jean Joseph Le Verrier
        Triton     1846   William Lassell
        Hyperion   1848   William Cranch Bond
        Ariel      1851   William Lassell
        Umbriel    1851   William Lassell
        Phobos     1877   Asaph Hall
        Deimos     1877   Asaph Hall
        Amalthea   1892   Edward Emerson Barnard
        Phoebe     1898   William Henry Pickering

## The 20th Century

So far, in 20th century 40 more major bodies (and thousands of comets and asteroids) have been discovered (27 by the Voyager probes) more than doubling the count again to 71:

        Himalia    1904   C. Perrine
        Elara      1905   C. Perrine
        Pasiphae   1908   P. Melotte
        Sinope     1914   S. Nicholson
        Pluto      1930   Clyde W. Tombaugh
        Carme      1938   S. Nicholson
        Lysithea   1938   S. Nicholson
        Miranda    1948   Gerard Kuiper
        Nereid     1949   Gerard Kuiper
        Ananke     1951   S. Nicholson
        Janus      1966   Audouin Dollfus
        Leda       1974   Charles T. Kowal
        Charon     1978   J. Christy
        Adrastea   1979   D. Jewitt & E. Danielson
        Metis      1979   Stephen Synnott
        Thebe      1979   Stephen Synnott
        Epimetheus 1980   R. Walker
        Atlas      1980   R. Terrile
        Calypso    1980   Pascu et. al.
        Helene     1980   P. Laques & J. Lecacheus
        Pandora    1980   S. Collins et. al.
        Prometheus 1980   S. Collins et. al.
        Telesto    1980   Reitsema et. al.
        Puck       1985   Voyager 2
        Belinda    1986   Voyager 2
        Bianca     1986   Voyager 2
        Cordelia   1986   Voyager 2
        Cressida   1986   Voyager 2
        Desdemona  1986   Voyager 2
        Juliet     1986   Voyager 2
        Ophelia    1986   Voyager 2
        Portia     1986   Voyager 2
        Rosalind   1986   Voyager 2
        Despina    1989   Voyager 2
        Galatea    1989   Voyager 2
        Larissa    1989   Voyager 2
        Naiad      1989   Voyager 2
        Proteus    1989   Voyager 2
        Thalassa   1989   Voyager 2
        Pan        1990   Showalter

Space History

##### Calvin J. Hamilton