PARIS (AFP) - Astronomers say they have detected nearly two dozen more satellites orbiting Jupiter, bringing the number of moons encircling the Solar System's greatest planet to an astonishing 60.
The 23 newcomers are tiny objects between just two and eight kilometers (1.1 and five miles) across, making them the smallest moons ever to be detected from Earth.
The discoverers, Scott Sheppard and David Jewitt of the Institute for Astronomy at the University of Hawaii, have already notched up many jovian moons to their credit.
The newly-found satellites have tilted, irregular orbits, which suggests they were lonely bodies that wandered the heavens until, billions of years ago, they were sucked into Jupiter's gravitational maw and never escaped.
Jupiter now has 52 of these "irregulars," according to their tally, which is reported on Thursday in Nature, the weekly British science weekly.
In contrast to these are Jupiter's eight "regular" satellites.
These are believed to have condensed from the same cloud of gas and dust that formed their parent, and circle the planet close in, tracking in tidy, circular, equatorial orbits.
The discovery restores Jupiter to its pre-eminence as the planet with the most moons.
The gassy giant accounts by itself for nearly half of the 128 known planetary moons in the Solar System.
Its closest rivals are Saturn, with 31 detected so far, followed by Uranus, with 21, and Neptune, 11.
The discovery is technically significant, because it shows how high-powered telescopes combined with modern computers can capture tiny objects in irregular orbits.
University of Maryland astronomer Douglas Hamilton believes the jovian king "will dominate the moon count for the foreseeable future," partly because it is closer to the Sun than the others and so its moons reflect more light.
The huge boost in moon detections poses something of a headache for the International Astronomical Union (IAU), the Paris-based association that vets astronomers' claims and attributes names to their discoveries.
The nomenclature of jovian moons builds on a tradition dating back to 1613, when Dutch astronomers Johannes Kepler and Simon Marius thought it would be fun to name them after Zeus' many lovers. Jupiter is the Latin name for Zeus, the ruler of the Olympian gods.
As Zeus had a long list of amorous conquests, it was quite easy to baptise new moons as they were gradually identified over the centuries.
But in recent years, dozens more moons have been added to the list.
The IAU has thus had to go beyond Zeus' little black book, and name the new moons after children or relatives of the lovers.
The last big update was in December 2002, when Themisto, a jealous child-killer; Taygete, a beautiful virgin who committed suicide; and Harpalyke, a hunter-warrior who could outrun a horse, were among 11 admitted to the list.
"The most beautiful thing we can experience is the mysterious." - Albert Einstein
Posted 20 May 2003 - 05:39 PM
I suppose it might actually become necessary to redefine what can be classed as a 'moon', since a lot of the moons of Jupiter for example are very small indeed, some only a few kilometres across.
Perhaps moons that are of a much larger size, such as Europa, Io, Ganymede, our moon etc. should retain the 'moon' title, whereas smaller ones should simply be referred to as natural satellites for example.
Still, I doubt there will ever really be a practical reason for altering the definition of the word 'moon', not unless they discover thousands more smaller ones in orbit around Jupiter and have a need to better seperate references to them from their much larger neighbours.