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Posted by Sam Wormley on February 26, 2009, 6:07 pm
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INSIDE SCIENCE RESEARCH---PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Research News
Number 881 February 26, 2008 www.aip.org/pnu
GREAT RED SPOT NOT AS GREAT
The hurricanes that visit the Gulf and Caribbean in September and
even the huge jetstream that dominates winter weather in North
America are small compared to Jupiter's Great Red Spot. The Spot is
a lozenge-shaped storm and is about two Earth-widths across. Like
meteorologists who study earthly hurricanes to better understand the
behavior of these violent storms, planetary astronomers try to
record detailed images of the Spot to better to understand weather
on Jupiter---a planet (with no visible solid surface at all) that is
nothing but weather.
Detailed images are hard to come by since the Great Red Spot is
always on the go. First, the planet as a whole is rotating. Then
the Spot is moving along its horizontal band, a cloud band
stretching all the way around the planet. Then this band is moving
relative to some of the other parallel bands at other latitudes.
Furthermore, the Spot is revolving counterclockwise about once every
6 Earth-days. Finally, the camera taking pictures, mounted on flyby
missions like the Galileo or Cassini spacecraft, are themselves
shooting through space at thousands of miles per hour.
Xylar Asay-Davis, a scientist at the University of California at
Berkeley, says that a further complication in sizing up the Spot is
the fact that various clouds not actually part of the Spot are
hovering nearby. Some of these clouds nip off parts of the Spot or
are, in their turn, taken up into the Spot. The only true way to
measure the true extent and motion of the Great Red Spot, he says,
is to measure wind speeds.
For that purpose, Asay-Davis and his colleagues have produced the
best ever map of wind speeds on Jupiter, where the gusts are
typically at the level of 250 miles per hour, higher than winds we
see in hurricanes on Earth. The maps consist of tens of millions of
velocity measurements and provide a sharp image of what's happening
with the Spot. Indeed, according to Xylar Asay-Davis these maps
represent the highest resolution and highest accuracy full-planet
map ever produced.
The maps draw on data from Galileo and Cassini and even observations
from the Hubble Space Telescope, and are processed with
sophisticated software. From all this number crunching, the team of
scientists deduce that the Great Red Spot has shrunken over the past
dozen years. The Spot has survived for at least 300 years and is
in no danger of dissipating, says Asay-Davis. Those nearby clouds,
regularly bumping into Spot can subtract or add energy from it.
Asay-Davis's reported his findings at a meeting of the American
Physical Society fluid dynamics division.
***********
PHYSICS NEWS UPDATE is a digest of physics news items arising
from physics meetings, physics journals, newspapers and
magazines, and other news sources. It is provided free of charge
as a way of broadly disseminating information about physics and
physicists. For that reason, you are free to post it, if you like,
where others can read it, providing only that you credit AIP.
Physics News Update appears approximately once a week.
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Posted by tadchem@comcast.net on February 26, 2009, 6:40 pm
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> INSIDE SCIENCE RESEARCH---PHYSICS NEWS UPDATE
> The American Institute of Physics Bulletin of Research News
> Number 881 =A0February 26, 2008 =A0 =A0 =A0www.aip.org/pnu
> GREAT RED SPOT NOT AS GREAT
"Out, damn'd spot! out, I say! ... Yet who would have thought the old
man to have had so much blood in him?"
Tom Davidson
Richmond, VA
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Posted by rmollise on February 28, 2009, 8:49 am
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> > INSIDE SCIENCE RESEARCH---PHYSICS NEWS UPDATE
> > The American Institute of Physics Bulletin of Research News
> > Number 881 =A0February 26, 2008 =A0 =A0 =A0www.aip.org/pnu
> > GREAT RED SPOT NOT AS GREAT
> "Out, damn'd spot! out, I say! ... Yet who would have thought the old
> man to have had so much blood in him?"
> Tom Davidson
> Richmond, VA
What a sigh is there! The heart is sorely charged.
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> The American Institute of Physics Bulletin of Research News
> Number 881 =A0February 26, 2008 =A0 =A0 =A0www.aip.org/pnu
> GREAT RED SPOT NOT AS GREAT