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RE: Saturn's rings
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Cassini Sees Saturn Rings Oscillate Like Mini-Galaxy

Scientists believe they finally understand why one of the most dynamic regions in Saturn's rings has such an irregular and varying shape, thanks to images captured by NASA's Cassini spacecraft. And the answer, published online today in the Astronomical Journal, is this: The rings are behaving like a miniature version of our own Milky Way galaxy.
This new insight, garnered from images of Saturn's most massive ring, the B ring, may answer another long-standing question: What causes the bewildering variety of structures seen throughout the very densest regions of Saturn's rings?

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Planetary ring systems
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Planetary ring systems are complicated, notes UW Space Place Director Jim Lattis, and they are more common than once believed.
For ages, Saturn was thought to be the only planet in our solar system with a ring system. But in recent years ring systems have been discovered around Jupiter, Uranus and Neptune as well.

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Saturn's rings may have formed when a large moon with an icy mantle and rocky core spiralled into the nascent planet.
A US scientist has suggested that the tidal forces ripped off some of the moon's mantle before the actual impact.
The theory could shed light on the rings' mainly water-ice composition that has puzzled researchers for decades.

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Saturn's F ring
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Cassini Sees Moon Building Giant Snowballs in Saturn Ring

While orbiting Saturn for the last six years, NASA's Cassini spacecraft has kept a close eye on the collisions and disturbances in the gas giant's rings. They provide the only nearby natural laboratory for scientists to see the processes that must have occurred in our early solar system, as planets and moons coalesced out of disks of debris.
New images from Cassini show icy particles in Saturn's F ring clumping into giant snowballs as the moon Prometheus makes multiple swings by the ring. The gravitational pull of the moon sloshes ring material around, creating wake channels that trigger the formation of objects as large as 20 kilometres in diameter.

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Researchers track 'propeller moons' around Saturn for insight into solar system formation

For the first time, astronomers have identified and tracked individual moons that are not in empty space, but nestled within a disk of debris orbiting a planet. The ability to watch as the embedded moons' orbits evolve over time could give scientists valuable new clues about how planets form and grow around stars in young solar systems.
Using images obtained by NASA's Cassini mission, astronomers led by Cornell research associate Matthew Tiscareno followed several of what are likely to be dozens of small moons orbiting within the outer edge of Saturn's A ring -- the outermost of the planet's large, dense rings -- from 2005 to 2009. They found that the moons' orbits evolved slightly over time, hinting that their paths may be influenced by interactions with the disk material surrounding them.

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Propeller moons
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Title: Physical characteristics and non-keplerian orbital motion of "propeller" moons embedded in Saturn's rings
Authors: Matthew S. Tiscareno, Joseph A. Burns, Miodrag Sremcevic, Kevin Beurle, Matthew M. Hedman, Nicholas J. Cooper, Anthony J. Milano, Michael W. Evans, Carolyn C. Porco, Joseph N. Spitale, John W. Weiss

We report the discovery of several large "propeller" moons in the outer part of Saturn's A ring, objects large enough to be followed over the 5-year duration of the Cassini mission. These are the first objects ever discovered that can be tracked as individual moons, but do not orbit in empty space. We infer sizes up to 1--2 km for the unseen moonlets at the centre of the propeller-shaped structures, though many structural and photometric properties of propeller structures remain unclear. Finally, we demonstrate that some propellers undergo sustained non-keplerian orbit motion. 

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RE: Saturn's rings
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This image of Saturn was taken by the Cassini spaceprobe on the 13th February, 2010, when it was approximately 313,359 kilometres away.
The image was taken using the CL1 and RED filters.

SATURNRINGb.jpg
Expand (11kb, 1024 x 768)
Credit: NASA/JPL/Space Science Institute


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This image of Saturn's rings was taken by the Cassini spacecraft on the 1th January, 2010 when it was approximately 610,617 kilometres away.
The image was taken using the CL1 and CL2 filters.

satring110110cb.jpg
Expand (75kb, 560 x 560)
Credit: NASA/JPL/Space Science Institute


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This image of Saturn's rings was taken by the Cassini spacecraft on the 1th January, 2010 when it was approximately 643,303 kilometres away.
The image was taken using the CL1 and CL2 filters.

satring110110ab.jpg
Expand (65kb, 560 x 560)
Credit: NASA/JPL/Space Science Institute


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Ghostly "Spokes" Puff Out From Saturn's Rings
Massive, bright clouds of tiny ice particles hover above the darkened rings of Saturn in an image captured by the Cassini spacecraft on Sept. 22, 2009, around the time of Saturn's equinox.
During this period, sunlight hits the rings edge-on and shines directly over the equator. The levitating icy particle clouds, which are known as "spokes" and are as wide as 10,000 kilometres, appear particularly dramatic because of the unique lighting geometry of the equinox period.
The particles that make up spokes levitate above the ring plane when they acquire an electrostatic charge, the way static electricity on Earth can raise the hair on your arms. The spoke particles appear to acquire more charge during dim conditions and, during equinox, the bulk of the rings are in shadow. That angle of light also brightens features that stick out of the ring plane.

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