Appendix 3:

Chronology of Solar System Discovery

Prior to 1600

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

plus the "fixed" stars. These are the ones that can be seen easily without any optical instruments. 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 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
    Europa     1610   Galileo
    Ganymede   1610   Galileo
    Io         1610   Galileo
    Titan      1655   Huygens
    Iapetus    1671   Cassini
    Rhea       1672   Cassini
    Dione      1684   Cassini
    Tethys     1684   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   Herschel
    Oberon     1787   Herschel
    Titania    1787   Herschel
    Enceladus  1789   Herschel
    Mimas      1789   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 double the 17th century total):

    Neptune    1846   Adams, Le Verrier
    Triton     1846   Lassell
    Hyperion   1848   Bond
    Ariel      1851   Lassell
    Umbriel    1851   Lassell
    Phobos     1877   Hall
    Deimos     1877   Hall
    Amalthea   1892   Barnard
    Phoebe     1898   Pickering

The Early 20th Century

In the first three quarters of the 20th century 13 more major bodies (and thousands of comets and asteroids) were discovered bringing the total up to 43:

    Himalia    1904   Perrine
    Elara      1905   Perrine
    Pasiphae   1908   Melotte
    Sinope     1914   Nicholson
    Pluto      1930   Tombaugh
    Carme      1938   Nicholson
    Lysithea   1938   Nicholson
    Miranda    1948   Kuiper
    Nereid     1949   Kuiper
    Ananke     1951   Nicholson
    Janus      1966   Dollfus
    Leda       1974   Kowal
    Charon     1978   Christy

The Space Age

27 more small moons were discovered by the two Voyager spacecraft:

    Adrastea   1979   Jewitt
    Metis      1979   Synnott
    Thebe      1979   Synnott
    Epimetheus 1980   Walker
    Atlas      1980   Terrile
    Calypso    1980   Pascu et. al.
    Helene     1980   Laques et. al.
    Pandora    1980   Collins et. al.
    Prometheus 1980   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

The CCD Age

Dozens more small moons have been discovered in recent years with large ground based telescopes and CCD cameras. There are well over 100 now known; See JPL's site for more details.

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Bill Arnett; last updated: 2003 Jan 22