Fwd: Buzzing Like A Beehive: Uranus Now Swarming With Distant Moons
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Subject: Buzzing Like A Beehive: Uranus Now Swarming With Distant
Moons
Date: 21 Sep 1999 15:29 UT
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Harvard-Smithsonian Center for Astrophysics Press Release
For Release: September 20, 1999
http://cfa-www.harvard.edu/cfa/ep/uranus92099.html
BUZZING LIKE A BEEHIVE: URANUS NOW SWARMING WITH DISTANT MOONS
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
team 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,
mho...@cfa.harvard.edu, 617-496-7775, http://cfa-www.harvard.edu/~mholman
Canada:
J.J. Kavelaars, McMaster University, kave...@physics.mcmaster.ca,
905-525-9140 x2716
France:
Brett Gladman, Observatory of Nice, gla...@obs-nice.fr, 011 33 4
9200
3126, http://www.obs-nice.fr/gladman (English and French versions)
Jean-Marc Petit, Observatory of Nice, pe...@obs-nice.fr, 011 33 4
9200
3126
Hans Scholl, Observatory of Nice, sch...@obs-nice.fr, 011 33 4 9200
3041