Astronomers find possible 17th Jupiter moon

Jupiter

July 22, 2000
Web posted at: 11:01 p.m. EDT (0301 GMT)

WASHINGTON (Reuters) -- Astronomers have discovered what could be a 17th moon for Jupiter, the first previously unknown satellite for the big planet in more than a quarter century.

Known for now only as S/1999 J1, the jovian moon is perhaps 3 miles across, making it the smallest moon ever found for any of the major planets in our solar system.

Among Jupiter's moons, this discovery is one of a group with highly eccentric orbits -- they travel around the big planet in the opposite direction from the others -- an average distance of 15 million miles from Jupiter, the astronomers said.

This is the first satellite for the solar system's largest planet to be found since 1974, according to scientists at the University of Arizona and at the Smithsonian Astrophysical Observatory in Massachusetts.

They announced their findings in a statement late on Friday.

The scientific teams have not yet assigned a permanent number, let alone a name, to the moon. This will happen after they more reliably confirm its orbit around Jupiter.

Astronomers first spied the new moon as part of the Spacewatch program, while they were scanning the skies for comets and asteroids last year. One object they saw was treated as if it were an asteroid, and designated as 1999 UX18.

But this object was moving more like a comet than an asteroid, even though it did not really look like a comet, the astronomers said.

Scientists in Arizona and at the Smithsonian's Minor Planet Center did not fully realize that the object was a new jovian moon until this month, when orbital calculations showed it was not an asteroid orbiting the sun, but rather a previously unknown moon going around Jupiter.

Jupiter and its moons will be too close to the sun to be detected by Spacewatch for another few months, although larger telescopes might recover it sooner, the astronomers said.

Before this, the smallest known moon for Jupiter was Leda, discovered in 1974, which is about 5 miles to 10 miles in diameter.

Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

CNN fyi.com: By the light of the fiery moon
June 28, 2000
Galileo spots new volcanoes on Io
June 1, 2000
Images reveal lakes, snow, geysers on Jupiter moon Io
May 19, 2000
Images reveal perils, oddities of Jupiter's inner moons
April 25, 2000
Spacecraft snaps close-ups of a lava flow on Io
April 20, 2000
Galileo, Cassini to study Jupiter in joint expedition
March 9, 2000

The University of Arizona
Smithsonian Astrophysical Observatory
The Spacewatch Project