JPL: Cassini Sees Saturn Rings Oscillate Like Mini-Galaxy

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JPL: Cassini Sees Saturn Rings Oscillate Like Mini-Galaxy

Post by bystander » Mon Nov 01, 2010 11:32 pm

Cassini Sees Saturn Rings Oscillate Like Mini-Galaxy
NASA JPL CICLOPS | 2010-363 | 01 Nov 2010
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?

Another finding from new images of the B ring's outer edge was the presence of at least two perturbed regions, including a long arc of narrow, shadow-casting peaks as high as 3.5 kilometers (2 miles) above the ring plane. The areas are likely populated with small moons that might have migrated across the outer part of the B ring in the past and got trapped in a zone affected by the moon Mimas' gravity. This process is commonly believed to have configured the present-day solar system.

"We have found what we hoped we'd find when we set out on this journey with Cassini nearly 13 years ago: visibility into the mechanisms that have sculpted not only Saturn's rings, but celestial disks of a far grander scale, from solar systems, like our own, all the way to the giant spiral galaxies," said Carolyn Porco, co-author on the new paper and Cassini imaging team lead, based at the Space Science Institute, Boulder, Colo.

New images and movies of the outer B ring edge can be found at http://www.nasa.gov/cassini, [url]http://saturn.jpl.nasa.gov%20and%20http://ciclops.org[/url].
Event: A Story of Saturn's Rings
CICLOPS | 01 Nov 2010
Complex, galaxy-like behavior of the outer edge of Saturn's B ring, the controlling gravitational influence of Saturn's moon Mimas, mountainous structures along the B ring's edge reaching 3.5-km high, and a lone moonlet orbiting nearby are all part of a story derived from examination of four year's worth of Cassini images, published today in the Astronomical Journal. From it have come long-sought insights into the origin of the chaotic structures in the densest portions of Saturn's rings, and a hint of what the early history of this part of the rings might have been like.
Galactic Behavior for the Outer B Ring

Keeping a close watch on the outer portion of Saturn's B ring, NASA's Cassini spacecraft records the complex inward and outward movement of the edge of the ring. This ring movement resembles the suspected behavior of spiral disk galaxies.

The position of the outer edge of the B ring, shown here crossing the middle of the frame, varies with time in this concatenation of 301 images taken an average of 1 minute, 50 seconds apart, over the span of about nine hours. The total variation of the edge, from the innermost to outermost locations, is 200 kilometers (120 miles). The eccentric Huygens Ringlet, another very narrow ringlet discovered by Cassini, and the innermost of the bands of ring material in the Cassini Division, a low-density region once thought to be empty, all appear in the top of the frame.

Flash Movie 23.8 MB
Quicktime 29.3 MB
Oscillations at B Ring Edge

This movie, made from images obtained by NASA's Cassini spacecraft of the outer edge of Saturn's B ring, reveals the combined effects of a tugging moon and oscillations that can naturally occur in disks like Saturn's rings and spiral galaxies.

The B ring is shown at the lower left of the frame, and its outer edge varies with time, moving in and out in this concatenation of 92 images, each taken about 6 minutes apart, over the span of 9 hours, 30 minutes. The Cassini Division, the division between the A and B rings once thought to be empty, dominates the upper right of the frame. The Huygens Ringlet runs across the middle of the frame from the upper left to lower right.

Flash Movie 11.2 MB
Quicktime 6.8 MB
Strange Things Afoot in the B Ring

The outer edge of Saturn's B ring exhibits an unexpected feature in this movie made from images captured by NASA's Cassini spacecraft. The images were obtained early in the planet's equinox "season" -- the period leading up to and away from August 11, 2009 when the sun was over the planet's equator and lit the rings exactly edge on.

The B ring is shown at the top of the frame. The Cassini Division, a low-density region that separates the A and B rings, dominates the middle of the frame. The inner A ring is at the bottom.

Flash Movie 2.9 MB
Quicktime 5.1 MB
Long Spiky Shadows

Vertical structures in the variable outer edge of Saturn's B ring cast shadows in these two images captured by NASA's Cassini spacecraft shortly after the planet's August 2009 northern vernal equinox.

In these two images, Cassini's narrow angle camera captured a 20,000-kilometer-long (12,000-mile-long) section arcing along the outer edge of the B ring in Saturn's rings. This particular section of the ring is known to be the site of vertical structures as tall as 3.5 kilometers (2.2 miles). See PIA11668 to learn more.

The B ring is shown at the top of both frames. The Cassini Division, a low-density ring region that separates the B ring from the A ring, runs from the bottom right to the upper left of the images. The A ring is at the bottom.
The Tallest Peaks

Vertical structures, among the tallest seen in Saturn's main rings, rise abruptly from the edge of Saturn's B ring to cast long shadows on the ring in this image taken by NASA's Cassini spacecraft two weeks before the planet's August 2009 equinox.

Part of the Cassini Division, between the B and the A rings, appears at the top of the image, showing ringlets in the inner division.

In this image, Cassini's narrow angle camera captured a 1,200-kilometer-long (750-mile-long) section arcing along the outer edge of the B ring. Here, vertical structures tower as high as 2.5 kilometers (1.6 miles) above the plane of the rings -- a significant deviation from the vertical thickness of the main A, B and C rings, which is generally only about 10 meters (about 30 feet).
A Small Find near Equinox

The Cassini spacecraft captured this image of a small object in the outer portion of Saturn's B ring casting a shadow on the rings as Saturn approached its August 2009 equinox.

The new object, situated about 650 kilometers (400 miles) inward from the outer edge of the B ring, was found by the presence of a localized bright feature and the detection of its shadow, which stretches 36 kilometers (22 miles) across the rings. Cassini scientists suspect the object is a solid moonlet, as opposed to a diffuse debris cloud, as might result from an impact, because no shadows have been observed accompanying any known impact plumes observed by Cassini. The shadow's length implies that the moonlet is protruding about 150 meters (500 feet) above the ring plane. If the moonlet is orbiting in the same plane as the ring material surrounding it, which is likely, it must be about 300 meters (1,000 feet) from bottom to top. However, the width of the bright feature implies that the moonlet must be several times wider than that height.
Credit: NASA/JPL/SSI

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