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Harvard-Smithsonian Center for Astrophysics Press Release
For Release: September 20, 1999


Until just a few years ago, many astronomers believed the planet Uranus 
was a bit strange. That's because, unlike the other giant  members of the 
Solar System, Uranus did not appear to have any so-called  irregular 
satellites, or, distant moons with unusual orbits. However, recent 
observations have found what appear to be three new irregular moons 
around Uranus, thus suggesting that the seventh planet from the Sun is 
just one of the gang after all.

Using the Canada-France-Hawaii Telescope (CFHT) on Mauna Kea, Hawaii,
an international team of astronomers made very careful observations over 
the summer to find these extremely faint objects. If confirmed, and tallied 
with two other irregular satellites discovered in 1997, Uranus would have 16 
regular and five irregular moons, making it the most populated planetary 
satellite system known.

Irregular satellites do not follow the normal, near-circular orbits of most 
satellites, such as the Earth's Moon. Instead, these irregular objects either 
travel in highly elliptical orbits, or follow paths that are severely tipped to 
the plane of the planet's equator.

"The discovery of these irregular satellites is very important because it 
means that Uranus is not some oddball, but rather is just like Neptune, 
Saturn, and Jupiter," says Matthew Holman, a planetary scientist at
the  Harvard-Smithsonian Center for Astrophysics and a member of the 
team that made the discovery. "It might also help us better understand 
how the irregular satellites of the giant gas planets originated and how
they've evolved."

These newly discovered objects are being referred to as "candidate"
irregular satellites because further observations are necessary to
absolutely confirm that these bodies are not comets or asteroids on
planet-encountering orbits. However, based on the data so far, the eam
is confident these are true moons of Uranus. "Given how these bodies 
are following the planet exactly, it is highly unlikely that these are  some 
sort of Solar System interlopers," says Brett Gladman of the Observatory
 of Nice, France, and leader of the team. Gladman and his colleague J.J. Kavelaars of McMaster University, Canada, were both members of the
team that found Uranus's first two irregular moons in 1997.

The three new candidate satellites were discovered in a search using the
world-class wide-field imaging camera, known as CFH12K, which is a 
mosaic of CCD detectors covering a very large patch of sky (currently 
35x28 arcmin,  or roughly the area of the full moon). This instrument 
allowed the team to  explore more than 90 percent of the region around
Uranus in which satellite  orbits are stable and to find these extremely 
faint objects, which are no more  than 20 kilometers in diameter and orbit 
Uranus at a distance of 10 to 25  kilometers.

Other members of the discovery team include Jean-Marc Petit and Hans 
Scholl  (Observatory of Nice, France), and P. Nicholson and J. A.Burns 
(Cornell University.)  Follow-up observations were obtained at the Mount 
Palomar 5-meter and Kitt Peak  4-meter telescopes, the latter in 
conjunction with D. Davis and C. Neese of the  Planetary Science Institute 
in Tucson, AZ. Brian Marsden and Gareth Williams of the International 
Astronomical Union's Minor Planet Center computed preliminary orbits for 
the reported objects.

Contact information:

United States:
Matthew Holman, Harvard-Smithsonian Center for Astrophysics,
mholman@cfa.harvard.edu, 617-496-7775,

J.J. Kavelaars, McMaster University, kavelaars@physics.mcmaster.ca,
905-525-9140 x2716

Brett Gladman, Observatory of Nice, gladman@obs-nice.fr, 011 33 4 9200
3126, http://www.obs-nice.fr/gladman (English and French versions)
Jean-Marc Petit, Observatory of Nice, petit@obs-nice.fr, 011 33 4 9200
3126  Hans Scholl, Observatory of Nice, scholl@obs-nice.fr, 
011 33 4 9200 3041


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