SATURN SWARMING WITH SATELLITES


Saturn re-takes the lead as the planet with the most known satellites following the discovery of at least 4 additional moons of that planet announced 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, Observatoire de la Cote d'Azur; JJ Kavelaars, McMaster University, Canada; Matthew Holman and B. Marsden, Harvard-Smithsonian Center for Astrophysics; and Phil Nicholson and Joseph Burns of Cornell University.

The four faint bodies were spotted during the last two months at several telescopes around the world. Orbital calculations indicate that the objects are almost certainly new satellites of the giant planet.

The first two moon candidates, which were described on Oct. 26th in an electronic circular of the International Astronomical Union (IAU), were spotted using the European Southern Observatory's 2.2m telescope in Chile. Upon analyzing the images taken August 7th 2000 Gladman (an expatriate canadian) realized that two faint moving objects he uncovered near the glare of brilliant Saturn could very well be new satellites of that planet.

On September 23rd and 24th, Gladman and Kavelaars were observing at the Canada-France-Hawaii 3.5-m telescope on Mauna Kea (Hawaii). In a more extensive search, they re-observed the two objects discovered in Chile, and produced two more candidates. Working as fast as the images came off the telescope, they were able to alert other teams of astronomers of the discoveries.

Additional confirming observations over the next few days came from R.L. Allen (Univ. of Michigan) at the 2.4-m MDM telescope in Arizona, C. Hergenrother and S. Larson at Steward Observatory's 1.5-m telescope also in Tucson, and A. Doressoundiram and J. Romon at the ESO New Technology Telescope in Chile (just beside the 2.2m telescope on which the first two were discovered).

The orbital calculations developed for the IAU circulars, and performed by Brian Marsden of the IAU Minor Planet Center in Boston, prove that these objects cannot be foreground asteroids; although it is currently impossible to prove that these are not comets passing fortuitously near Saturn, previous experience has shown that this is highly unlikely.

Several months of continued observation will be required to firmly establish the orbits of these objects.

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.

Saturn previously had only one known irregular satellite (named Phoebe and discovered in 1898 by William Pickering) in contrast to Jupiter's nine (one of which was discovered last year), Neptune's two, and the 5 irregulars of Uranus (also discovered by this team, in 1997 and 1999).

Saturn's total count of 22 moons now surpasses that of Uranus (with 21). The new moons of Saturn have diameters ranging from 10-50 kilometers (about 5-30 miles), in line with the sizes of other irregular moons.

The team has several other satellite candidates that are being tracked to confirm their identities as satellites. It looks like there is a rich system of small distant moons swarming around the beautiful 'ringed planet'.

For more informations:

Professor JJ Kavelaars
Phone: (905) 525-9140 (x27106)
Email: kavelaars@physics.mcmaster.ca

Additional information can be found via the web at
http://pinks.physics.mcmaster.ca/Saturn