Musings of a Renaissance Man

Saturn Moons

Saturn and Moons by Bryan Brandenburg

Saturn Moons

Saturn is currently known to have fifty-six moons, many of which were discovered very recently, and three additional un-confirmed, hypothetical moons. However, a precise number of moons can never be given, as there is no objective dividing line between the anonymous orbiting fragments that form Saturn’s ring system and the larger objects that have already been named as moons.

Before the advent of telescopic photography, eight moons of Saturn were discovered by direct observation using an optical telescope:

  • Titan, discovered in 1655 by Christiaan Huygens;
  • Tethys, Dione, Rhea and Iapetus (the “Sidera Lodoicea”) discovered 1671-1684 by Giovanni Domenico Cassini;
  • Mimas and Enceladus, discovered 1789 by William Herschel;
  • Hyperion, discovered 1848 by W.C. Bond, G.P. Bond and Lassell.

The use of long-exposure photographic plates made it possible to discover additional moons:

  • Phoebe was the first satellite discovered by telescopic photograph in 1899 by W.H. Pickering.
  • In 1966, the satellites Janus and Epimetheus were observed, but not confirmed, and it was not realized that there were two distinct moons sharing an orbit.

The study of the outer planets has since been revolutionized, first by the use of unmanned space probes, and then by advances in telescopy:

  • From 1980, when the first of the Voyager space probes arrived at Saturn, to 1990, analysis of Voyager images revealed eight more moons in the inner Saturnian system. The last discovered was Pan.
  • A survey starting in late 2000 found thirteen new moons orbiting Saturn at a great distance in orbits that suggest they are fragments of larger bodies captured by Saturn’s gravitational pull (Nature vol. 412, pp. 163–166).
  • The Cassini mission, which arrived at Saturn in the summer of 2004, discovered three small moons in the inner Saturnian system as well as three suspected but unconfirmed moons in the F Ring. This increased the total to thirty-seven moons, confirmed and unconfirmed.
  • On November 16, 2004, Cassini scientists announced that the structure of Saturn’s rings indicates the presence of several more moons orbiting within the rings, but only one, Daphnis, has been visually confirmed so far (its confirmation was announced on May 6, 2005).
  • On May 3, 2005, astronomers using the Mauna Kea Observatory announced the discovery of twelve more small outer moons.
  • On June 30, 2006, astronomers using the Subaru 8.2 m telescope announced the discovery of nine more small outer moons.

The spurious satellite Chiron, “discovered” in 1861, is now known not to exist. Themis, “discovered” in 1905, also was later proven not to exist.

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