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Spacewatch astronomers have discovered the first new moon of Jupiterto be uncovered since Voyager visited the planet in 1979.
By Andrew Bridges
Pasadena Bureau Chief
posted: 08:15 pm ET
21 July 2000
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jupiter_newmoon_000721 Careful observational work has turned up a new moon of Jupiter -- the 17th, and latest to be discovered orbiting the planet since Galileo first peered at the gas giant in 1610.Astronomers working with the Spacewatch program at the University of Arizona spotted the moon, provisionally dubbed S/1999 J 1, over the course of 14 observations made between October 6 and November 4, 1999.
The new moon can be seen moving up and to the left in these three images as it orbits Jupiter. credit: Spacewatch/Minor Planet Center At first, the astronomers suspected the object was a comet, but further calculations of its orbit completed with the assistance of scientists at the Minor Planet Center at the Smithsonian Astrophysical Observatory led them to conclude it was indeed a tiny moon. [inset] "When I saw its position, I said, Thats near Jupiter. That isnt a satellite, is it?" Brian Marsden, the Minor Planet Centers director, said. If confirmed by further observations, the tiny moon would the first Jovian satellite to be discovered since the spacecraft Voyager turned up three during its 1979 visit to the planet. "Some new measurements of the position of the object in the next two to three months would probably nail it," said Robert S. McMillan, Spacewatchs principal investigator. The tiny moon, perhaps only 3 miles (5 kilometers) across, would become the ninth of Jupiters known outer satellites, and the fifth of those to have a retrograde, or backward, orbit. The planet also has eight inner moons, including the four satellites first spotted by Galileo. 
Could this moon be a captured comet?
Hear an interview with Joe Montani, one of the Spacewatch astronomers who helped discover the new Jovian moon.
The newly discovered moon could well become the smallest moon known to orbit a major planet. (Asteroid 243 Idas satellite Dactyl, for example, is smaller.) Along with its four retrograde satellite sisters, Ananke, Carme, Sinope and Pasiphae, the new moon circles the planet in an irregular orbit 15 million miles (24 million kilometers) out. The moon takes an estimated 774 days to orbit the planet apparently making it the outermost of the planet's 17 natural satellites.If confirmed, the new moon would likely be named after a figure from Greek mythology associated with typically a lover of the god Jupiter.
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