Just as the Roman god Jupiter fathered scores of children in myth, so too does his planetary namesake appear to have a large family. Astronomers at the University of Hawaii recently discovered 11 new moons orbiting the solar system's largest planet, bumping the tally up to 39--more than that known for any other planet.
These satellites are visible as faint dots of light only a few kilometers long circling Jupiter at a maximum distance of 20 million kilometers, or 300 Jupiter radii, all moving in retrograde orbits counter to the direction of Jupiter's spin. They travel around the gas giant in distinct clusters, which suggests they are the shattered remnants of prior moons. That fact, combined with their irregular, elongated orbits, strongly hints that they were captured by Jupiter when the planet was young. During these early days of formation, proto-Jupiter's bloated atmosphere could have dragged in passing asteroids within the first million years of the solar system. Alternatively, the planetesimals may have been trapped by the planet's increasing gravity during its final stages of growth.
The research team found the new moons in mid-December 2001 using the Canada-France-Hawaii telescope, spending months monitoring these satellites to confirm their orbits. They announced the discovery of 11 other moons around Jupiter last year. The scientists plan to analyze these satellites' sizes, surfaces and orbits in the hopes of learning more about early planetary formation processes. Previously, Saturn was the record holder for most satellites, with 30 in its retinue.