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Seven Newfound Moons of Jupiter Bring Tally to 47
By Robert Roy Britt
Senior Science Writer
posted: 03:47 pm ET
05 March 2003
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Please Post today Editor's Note: Within two days of this story's publication, the tally inched up to 48. In what is becoming a routine announcement, the tally of Jupiter's known satellites has grown, this time by seven to a grand total of 47. The moons were announced today. More will surely be discovered as the search continues. Jupiter reigns as king of moons. Saturn has 30, Uranus 21 and Neptune 11. Each of these planets likely harbors more satellites, but because the planets are farther away, their moons are even harder to find than the mere specks of light spotted around Jupiter. Astronomers spot them by noting their movement compared with background stars. Mars has two moons and Earth has just one, although a separate effort recently uncovered a quasi-moon that carves an odd path that is gravitationally bound to our planet. Pluto also has a moon, Charon. All of the newfound Jovian satellites are small, estimated by their brightness to be between 1.2 and 2.4 miles (2 to 4 kilometers) in diameter. Jupiter has 17 other moons in this size range and several that aren't much bigger. Jupiter's largest moon, Ganymede, is about 3,270 miles (5,262 kilometers) wide. The newest known satellites were spotted in early February by a team led by Scott Sheppard and David Jewitt of the University of Hawaii's Institute for Astronomy, with Jan Kleyna of Cambridge University. Follow-up observations were done before today's announcement. The team's last big batch of little Jovian moons was announced last May. Jewitt told SPACE.com then that there might be as many as 100 satellites down to 0.62 miles (1 kilometer) in diameter, but he stressed that this was just a guess. He figures there are countless objects even smaller. In an e-mail interview today, Jewitt stuck by his estimate. He also said there could be unfound moons significantly bigger than those announced today, because all possible orbital configurations have not been investigated. He said his team will continue searching. | | | Jupiter's Satellite Count Grows to 48 with Discovery of Another Micromoon posted: 03:37 pm ET
07 March 2003 No sooner is the virtual ink virtually dry on our report of seven new Jovian moons than we have another one to report. This latest moon, a little thing at roughly 1.9 miles wide (3 kilometers), brings the giant planet's tally of known satellites to 48. The satellite, named S/2003 J8, was announced today. It was revealed to astronomers yesterday in a circular of the International Astronomical Union. It's a stretch to call S/2003 J8 a moon, really. This and more than two dozen other similarly small satellites of Jupiter are thought to be captured asteroids or chunks of larger space rocks that broke apart. Not serious swooning material. The satellite orbits opposite to Jupiter's direction of rotation. It was found and confirmed in observations made between Feb. 8 and March 5 by a team led by Scott Sheppard and David Jewitt of the University of Hawaii. -- RRB | Of the new objects, two follow what are considered normal "prograde" paths around the gas giant planet, travelling in the same direction as Jupiter spins. The other five travel in backward "retrograde" orbits, as do many of Jupiter's small moons. Astronomers do not know how all of these little satellites formed. Some may be captured asteroids. Others that appear to roam in packs might have resulted from collisions between larger objects. The satellites are named S/2003 J1 through S/2003 J7. In a statement, the astronomers said J1 and J6 are the prograde satellites, but that observations are preliminary and orbital information might change. The discoveries were made using the world's two largest digital cameras, at the Subaru and Canada-France-Hawaii telescopes on Mauna Kea in Hawaii. Follow-up observations were done with a smaller telescope at the University of Hawaii. Brian Marsden at the Harvard Center for Astrophysics made orbital calculations to aid in the discoveries. Another lone, small Jovian moon was found on Oct. 31, 2002, and is called S/2002 J1. SPACE.com has not previously reported that finding.
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