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University of British Columbia Press Release

EMBARGOED UNTIL TUESDAY, JUNE 3, 8:00 A.M. PST 

CANADIAN ASTRONOMERS FIND NEW MOONS OF JUPITER

Part 2 of 2

THIS YEAR

Because moons can sometimes appear in front of distant stars or lost
in the light scattered from the planet, to really find them all
requires painstakingly repeating the search several times. The team
has been doing this in Febuary, March, and April of 2003 and has
announced 9 new satellites and provided observations on all 21 of
this year's disoveries. The lastest announcement, named S/2003 J 21,
is another body in the cluster of satellites near Jupiter's moon
Ananke (the latter discovered in 1951). NRC astronomer Kavelaars
says: "The tracking of these extremely faint objects is extremely
difficult, but necessary for without many observations one cannot
calculate their orbits around the planet in order to learn about
their origin." The entire region around Jupiter has essentially been
re-examined many times during this spring, `picking up' the moons
which were by bad luck unseen on some of the nights. "Their
observational strategy involving pairs of nights of observations each
month has paid off", says Brian Marsden who has computed the orbits
of the satellites based on the observations. Satellites S/2003 J 13
through J 21 were announced with observations from this team and an
independent team at the University of Hawaii. 

AN INTERESTING ORBIT

Of all the jovian satellites discovered in the last two years, it is
the second to most recent one, S/2003 J 20 which stands out from the
pack. The canadian team has been tracking the satellite steadily this
year, improving its orbit and yielding two surprises. First, its
orbit stands apart from all other previously known Jupiter moons,
thus appearing not to be part of one of the known 'families' of
objects. Secondly, Valerio Carruba (Cornell University) has confirmed
that this object is lodged in an interesting orbital resonance with
Jupiter. It is in fact this Kozai resonance which sets the maximum
orbital inclination (orbital 'tilt' with respenct to the plane of our
Solar System) these moons can have, for if more inclined their orbits
would distort periodically every century and drop down into the
dangerous realm of Jupiter's larger (regular) satellites, which would
eliminate these small moons. The new satellite S/2003 J 20 is
protected by this resonance and undergoes a more limited osciallation
range, thus avoiding this fate.

THE FUTURE

The region around Jupiter has now been covered several times to the
faintless levels which can be reached. This means that except for a
trickle, the spree of irregular satellite discoveries that has
occurred since 1997 will slow because all the giant planets have now
been surveyed with modern technology. Novel observational techniques
will allow astronomers to discover a few fainter satellites (as has
recently been done for Neptune,) but this will not likely produce the
rush of discoveries that the deployment of the new generation of CCD
cameras has made possible.

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CONTACT INFORMATION

Brett Gladman
Available by phone Monday evening, June 3
4:30 PM--10 PM EASTERN time, at cell phone below
(604) 219-0093

Lynne Allen
Available by cell phone May 30-June 3
(604) 219-0093

JJ Kavelaars
Unavailable Tuesday, June 3
(519) 581-1109

Michelle Cook (UBC Press officer)
(604) 822-2048

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