> PRESS RELEASE
> Date Released: Tuesday, June 03, 2003
> Canadian Astronomical Society
>
> Irregular Satellites of Jupiter
>
> So far this year, Jupiter has gained 21 new distant
> satellites, with the
> most recent announcement of satellite S/2003 J 21 on
> June 3rd at the annual
> Canadian Astronomical Society (CASCA) meeting in
> Waterloo (ON). This puts
> Jupiter far ahead of the all other planets, with 61
> known moons. Astronomers
> from the University of British Columbia (Professor
> Brett Gladman and
> postdoctoral researcher Lynne Allen) and the
> National Research Council (Dr.
> JJ Kavelaars) of the National Research Council of
> Canada are the discovery
> team.
>
> The work has been made possible by the new Megaprime
> mosaic
> (http://www.cfht.hawaii.edu/News/MegaPrime/) of CCD
> cameras at the 3.6m
> Canada-France-Hawaii telescope.
>
> Information on the discoveries, the tracking effort,
> and new results are
> provided below. See also
>
> http://www.astro.ubc.ca/people/gladman/jup2003.html
>
> SIFTING THE SAND AT JUPITER
>
> Astronomers in Canada have been busy the last few
> months peering around the
> planet Jupiter to search for small new moons of that
> planet, extending a
> spree of moon discoveries begun in 1997. The current
> team of jovian
> searchers consists of UBC astronomers Brett Gladman
> and Lynne Allen, and JJ
> Kavelaars of the National Research Council of
> Canada. The international team
> includes Cornell University astronomers Phil
> Nicholson, Joseph A. Burns, and
> Valerio Carruba, Jean-Marc Petit of the Observatoire
> de Besancon, and Brian
> Marsden and Matthew Holman of the
> Harvard-Smithsonian Center for
> Astrophysics.
>
> Detecting satellites around gigantic Jupiter is a
> difficult undertaking
> because they can occupy a large patch of sky around
> the planet (making
> searching time consuming) and the feeble amounts of
> light they reflect back
> to us must compete against the glare of brilliant
> Jupiter. New and bigger
> detectors have made more complete searches possible,
> and twenty one new
> jovian satellites have been discovered this year.
>
> This boosts the number of known satellites of
> jupiter to sixty one. It now
> appears that each giant planet's irregular satellite
> population is the
> result of ancient collisions between former moon and
> passing comets or
> asteroids. "These collisions result in the
> production of families of
> satellites in similar orbits," said Gladman, "which
> seem to be the rule".
>
> NEEDLE IN A HAYSTACK
>
> The new satellites were a challenge to detect
> because most are only about
> 1-5 kilometers in size. Their small size and
> distance from the Sun prevent
> the satellites from shining any brighter than 24th
> magnitude, about 100
> million times fainter than can be seen with the
> unaided eye. To locate these
> new moons, the canadian team has been using the
> brand new Megaprime mosaic
> of CCD cameras at the 3.6m Canada-France-Hawaii
> telescope on Mauna Kea in
> Hawaii. Covering all the sky in which satellites
> could be found required
> this new large mosaic camera, enabling them to
> quickly obtain images of the
> entire sky around the planet in which the moons
> could be living. They used
> computer algorithms to search the images for the
> faint points of light
> moving across the sky in the manner expected for
> Jupiter moons. "Searching
> by eye through the 50 gigabytes of images each night
> would be an impossible
> task," says UBC postdoctoral fellow Lynne Allen, "so
> we must use powerful
> computers to sift through the data."
>
> 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 right on the
> edge of the stability region, barely 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.
>
> IMAGES
>
> Discovery image of S/2003 J 21 (postive B/W)
> http://www.astro.ubc.ca/people/gladman/J21disc1.jpg
>
> Discovery triplet of S/2003 J 21 (postive B/W). The
> faint moon (circled) can
> be seen moving relative to the background stars.
> http://www.astro.ubc.ca/people/gladman/J21disc.jpg
>
> Black and white image of a Megacam field near
> Jupiter (black/white positive
> image). The brilliant planet is just off the top of
> the field, producing a
> great deal of scattered light that confuses the
> search.
>
http://www.astro.ubc.ca/people/gladman/jup2003mpp.jpg
>
> Negative of the above image (negative image)
>
http://www.astro.ubc.ca/people/gladman/jup2003mpn.jpg
>
> Discoverers Gladman and Allen pointing out the
> jovian moon
> http://www.astro.ubc.ca/people/gladman/jupcagnes.jpg
>

=====
"Yo no sufro de locura... la disfruto cada minuto."
Les Luthiers.

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