posted on Oct. 26: Researchers discover four additional moons around Saturn


[img_inline align=”right” src=”” caption=”Saturn’s known satellites”]Saturn re-takes the lead as the planet with the most-known satellites following the discovery of at least four additional moons. The announcement was made today in Pasadena, California at a meeting of the Division for Planetary Science of the American Astronomical Society.

The discoveries were made by an international team of astronomers: Brett Gladman (an expatriate Canadian), Observatoire de la Cote d'Azur; JJ Kavelaars, McMaster University, Canada; Matthew Holman and Brian Marsden, Harvard-Smithsonian Center for Astrophysics; and Phil Nicholson and Joeseph A. Burns of Cornell University.

McMaster researcher JJ Kavelaars says, “The newly discovered irregular moons are small, about 10 to 50 kilometres across, in line with the size of other irregular moons. They are likely icy moons, the remnants of a long-ago capture event.”

Observed from Earth, these moons appear as faint dots of light moving around Saturn. Two of the moons were discovered using the European Southern Observatory's 2.2-meter telescope and the other two were discovered using the Canada-France-Hawaii telescope.
(Telescope images are available at

Several months of continued observation will be required to firmly establish the orbits of these objects. Saturn previously had only one known irregular satellite named Phoebe, discovered in 1898 by William Pickering. Saturn's total count of 22 moons now surpasses that of Uranus which has 21 moons.

These moons are what astronomers refer to as “irregular” moons because they are far from their planet and were likely captured into orbit after the planet formed. In contrast, the “regular” moons of the giant planets, which commonly have nearly circular, equatorial orbits nested close to their planets, are thought to have formed out of a disk of dust and gas that surrounded each planet as it formed.

The same group of astronomers is responsible for the discovery of nine irregular satellites over the past two years. In 1998 they reported the discovery of the first known irregular moons of the giant planet Uranus. Further exploration of Uranus in 1999 added another three moons. Since 1997 the group's work has nearly doubled the number of known irregular moons in the solar system.

The team is tracking several other candidates in the hopes of confirming their identities as satellites. It looks like there is a rich system of small distant moons swarming around the beautiful “ringed” planet. Continued observations of the Uranian system over the past two years are beginning to reveal the secret pasts of the irregular moons. These new discoveries around Saturn will provide additional information about the processes at work during the formation of the gas giant planets.

Photo above of Saturn's known satellites from Web site mentioned above