New Hubble, Keck images show turbulent Jupiter (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Thu, 22 May 2008 16:49:56 GMT
[http://www.berkeley.edu/news/media/releases/2008/05/22_redspots.shtml]
Media Relations
University of California-Berkeley
Contact:
Robert Sanders, Media Relations
Phone: (510) 643-6998
22 May 2008
New Hubble, Keck images show turbulent Jupiter
By Robert Sanders
BERKELEY -- Increased turbulence and storms first observed on Jupiter more
than two years ago are still raging, according to astronomers from the
University of California, Berkeley, and the W. M. Keck Observatory in
Hawaii, who snapped high-resolution pictures of the planet earlier this
month.
Captured with NASA's Hubble Space Telescope (HST) and the 10-meter Keck II
telescope, this so-called "major upheaval" on Jupiter involves stunning
changes in the planet's atmosphere, said lead astronomer Imke de Pater,
professor of astronomy at UC Berkeley.
The images are available on NASA's HubbleSite NewsCenter,
http://hubblesite.org/newscenter/archive/releases/2008/23/
The upheaval was heralded in December 2005 by a color change from white to
red of a large oval near the Great Red Spot, earning it the moniker Red
Spot Jr. This oval, formally known as Oval BA, formed six years earlier
through a merger of three large white ovals just south of the Great Red
Spot - storms that formed in the early 1930s and were prominent in the
Voyager era.
The new images, the first since Jupiter emerged from its passage behind
the Sun, may show that Jupiter indeed is undergoing a major climate
change, as predicted four years ago.
"One of the most notable changes we observe in both the Hubble and Keck
images is the change from a rather bland, quiescent band surrounding the
Great Red Spot just over a year ago to one that is incredibly turbulent at
both sides of the spot," de Pater said. "During all previous HST
observations and spacecraft encounters, starting with Voyager in 1979,
such turbulence was seen only on the west or left side of the spot."
The Great Red Spot is a persistent, high-pressure storm on Jupiter whose
cloud head sticks some 8 kilometers (5 miles) above the surrounding cloud
deck. Why the spots are red is a subject of great debate.
Moreover, the color of several bands on the planet has been changing since
the upheaval began, said Christopher Go, an amateur astronomer in Cebu,
the Philippines, who joined de Pater's team two years ago. Go alerted the
astronomical community in early 2006 about the color change of Red Spot
Jr.
"Lately, the red color of the Oval BA has faded a little bit, while the
Great Red Spot may have turned dark red," Go said.
The UC Berkeley team will work with the amateur astronomy community to
investigate the possible origin of this turbulence, which is not
understood.
The Great Red Spot and Red Spot Jr. are squeezed between bands called
shear flows, where the flow above each storm is moving westward and the
flow below is moving eastward. Since the shear flow in each band is
slightly different, and the storms are different sizes, Red Spot Jr.
drifts slowly eastward toward the Great Red Spot while the Great Red Spot
drifts slightly westward toward Red Spot Jr. In late June, this storm will
pass the Great Red Spot, as it does every two years.
Interestingly, a third red spot has appeared to the west of the Great Red
Spot in the same latitude band.
"Although much smaller in extent, the color is striking," said UC Berkeley
team member Michael Wong. "Like the other two large red storm systems,
this newest red spot is bright in near-infrared wavelengths and dark in
the ultraviolet. If this spot and the Great Red Spot continue on their
courses, they will encounter each other in August, and the small oval will
either be absorbed or repelled from the Great Red Spot."
According to Philip S. Marcus, a professor of fluid dynamics at UC
Berkeley, analysis of the Hubble and Keck images may support his 2004
conjecture that Jupiter is in the midst of global climate change that will
alter temperatures by as much as 10 degrees Celsius, getting warmer near
the equator and cooler near the south pole. He predicted that large
changes would start in the southern hemisphere around 2006, causing the
jet streams to become unstable and spawn new vortices.
"The appearance of the planet's cloud system from just north of the
equator down to 34 degrees south latitude keeps surprising us with changes
and, in particular, with new cloud features that haven't been previously
observed," Marcus said. "Whether or not Jupiter's climate has changed due
to a predicted warming, the cloud activity over the last two and a half
years shows dramatically that something unusual has happened."
"A major goal in taking the Hubble images is to look for changes in the
zonal wind profile since the Cassini encounter in 2000," added team member
Xylar Asay-Davis. "If we do find major changes, these could provide
important supporting evidence for climate change on Jupiter."
The red coloration in the ovals may be generated as their swirling hazes
rise to heights like the clouds of the Great Red Spot. Detailed analysis
of the Hubble's visible light data and the Keck images at near-infrared
wavelengths will reveal the relative altitudes of the cloud tops of the
three red ovals, de Pater said. Since all three oval storms are bright at
near-infrared wavelengths where methane gas is absorbing, the data already
show that all three systems rise up well above the surrounding cloud deck.
The Hubble telescope imaged the entire planet on May 9 and 10 using the
Wide-Field Planetary Camera 2, while Keck II focused on the area around
the Great Red Spot on May 11 using adaptive optics to sharpen the image.
Dr. Al Conrad, a support astronomer at the Keck Observatory, noted that
the team used adaptive optics (AO) to obtain a spatial resolution
comparable to that obtained at visible wavelengths with the Hubble
telescope. Adaptive optics can take the twinkle out of an object caused by
turbulence in the atmosphere, but to do this well, the target must be near
another bright object that can serve as a reference. For some of the
images, Jupiter's moon Europa was used as the reference "star." But until
Europa was visible off the limb of Jupiter, a laser guide star was created
near Jupiter to serve this purpose.
"This was our second attempt using the laser to obtain AO-corrected images
of Jupiter's surface," Conrad said. "Based on our past experience, we
placed the laser beacon slightly farther from Jupiter's bright glow. With
this adjustment in place, AO revealed much finer detail on the surface
than we saw during our previous observation. By using the laser whenever
there is no moon available as an AO reference, we will now have many more
opportunities to observe Jupiter with Keck."
In addition to images at 1.2-1.65 microns, where Jupiter's reflected
infrared light is measured, the team also obtained a close-up of the three
spots at the somewhat longer infrared wavelength of 5 microns that samples
thermal radiation from deeper in the atmosphere. All three spots appear
dark on the 5-micron image because the clouds obscure heat emanating from
lower elevations.
''This image is spectacular,'' says de Pater. "There is an amazing amount
of fine structure and numerous small ovals south of the spots. This image
reveals details in the cloud opacity not seen at the other wavelengths."
The W. M. Keck Observatory operates twin 10-meter telescopes located on
the summit of Mauna Kea on the island of Hawaii and is managed by the
California Association for Research in Astronomy, a non-profit corporation
whose board of directors includes representatives from Caltech, the
University of California and NASA. For more information, please visit the
W.M. Keck Observatory homepage,
http://www.keckobservatory.org/
The Hubble Space Telescope is operated by the Space Telescope Science
Institute with funding from NASA.
The Hubble team consisted of de Pater, Marcus, Wong and Asay-Davis of UC
Berkeley and Go of the Philippines. The Keck team members were de Pater,
Wong and Conor Laver of UC Berkeley and Conrad of the Keck Observatory.
The contributions by the amateur network
(http://jupos.privat.t-online.de/) was invaluable for this research.
.
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