SPACE.com -- By Jove! A New Moon

The photo shows the moving, point-like image of the newly discovered Jupiter moon, S/1999 J 1 low in the sky and just before sunrise on July 28, 2000. Several images were combined into an animated gif-image to visualize this motion

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	By Jove! A New Moon By Jove! A New Moon By posted: 10:59 am ET 07 August 2000

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WASHINGTON -- Add another mini-world to giant Jupiter's entourage of moons -- 17 Jovian satellites are now known.

Astronomers using European Space Observatory telescopes in Chile's Atacama desert region and in France obtained detailed information about the small moon, tagged object S1999 J1, confirming it as a natural satellite of Jupiter.

The object was first imaged in October and November 1999 by astronomers at the Spacewatch program at the University of Arizona in Tucson. Using a 36-inch (1-meter) telescope atop Kitt Peak, electronic scans were taken of a region of sky near Jupiter to survey for possible asteroids and comets.

One object detected at that time was given the asteroid designation 1999 UX18. It moved in a slightly unusual manner, suggesting that it might be a comet. Yet the object did not look like a comet.

Detective story of detection

Working jointly, experts at the Spacewatch program and the Smithsonian's Minor Planet Center in Massachusetts were able to conclude that the asteroid was a likely candidate satellite of Jupiter.

The object was then designated as S1999 J1, the first candidate satellite of Jupiter to be discovered in 1999.

Unfortunately, during the spring of 2000 Jupiter and the suspected moon were on the opposite side of the sun as seen from Earth. The faint object remained lost in the sun's glare. New observations were urgently needed to recover the object, and secure its orbit.

Using telescopes in the armada of instruments operated by the European Space Observatory (ESO), a search for S1999 J1 was undertaken last month. Over several days, ESO astronomers were able to confirm the moon's recovery.

The name game

The new moon belongs to the class of "irregular satellites" which move in non-circular and inclined orbits around Jupiter. Scientists believe this type of object was captured into its current orbit after Jupiter was formed.

S1999 J1 is one of the outermost moons of Jupiter known so far.

New observations of the object indicate that it must be comparatively small, with a diameter on the order of 6 to 9 miles (10 to 15 kilometers) in diameter.

The color of the newly discovered moon is very slightly red. That could mean the object is a captured asteroid, rather than a cometary nucleus. However, additional work to further define its origin is required.

When more observations of S1999 J1 are made, the moon will be given a name. According to astronomical tradition, that name will be selected from Greek mythology, and be approval by a special group of the International Astronomical Union established for planetary system nomenclature.

S1999 J1 is the first reasonably established outer satellite of Jupiter to be found since 1974.