[FPSPACE] Cornell astronomer describes 'an eerily beautiful sight' as Cassini mission find
ljk4 at msn.com
Wed Oct 25 09:22:57 EDT 2006
>From: Cornell Chronicle Online <cunews at cornell.edu>
>Reply-To: Cornell Chronicle Online <cunews at cornell.edu>
>To: CUNEWS-PHYSICAL_SCIENCE-L at cornell.edu (CUNEWS-PHYSICAL_SCIENCE-L),
>CUNEWS-SCIENCE-L at cornell.edu (CUNEWS-SCIENCE-L)
>Subject: Cornell Chronicle:
>Date: Tue, 24 Oct 2006 16:24:28 -0400
>News from Chronicle Online
>Cornell astronomer describes 'an eerily beautiful sight' as Cassini mission
>finds faint new rings around Saturn
>Oct. 24, 2006
>By Lauren Gold
>LG34 at cornell.edu
>Like suspended dust grains caught in a shaft of light, the tiniest of
>Saturn's ring particles were on glimmering display for 12 hours last month
>as NASA's Cassini spacecraft passed into Saturn's shadow and collected
>images of the ethereally backlit ring system.
>From this new perspective, Cassini caught sight of faint new rings in the
>system, including two orbiting along with their small parent moons outside
>the main ring system and two within the Cassini Division (the largest gap
>in the main ring system). The spacecraft had also spotted a dynamic rippled
>pattern in the system's innermost D ring.
>Cornell astronomers and colleagues on the Cassini team presented the latest
>data and images from the Saturn mission at a recent Division for Planetary
>Sciences meeting of the American Astronomical Society in Pasadena, Calif.
>The observations were made in September, as Cassini orbited 2.16 million km
>(1.4 million miles) from Saturn and looked down at the unlit side of the
>rings from 15 degrees above the ring plane.
>Using images from NASA's Voyager mission, which passed Saturn in the early
>1980s, astronomers can see how the rings are changing over time. A wispy
>new ring in the Cassini Division (named for its discoverer, 17th-century
>astronomer Giovanni Cassini), for example, isn't visible in any of the
>Voyager images; indicating that it may be younger than your average
>"Saturn's ring system is a very dynamic place, and it's changing as the
>mission sits there and watches it," said Cassini team member Joe Burns,
>Cornell's Irving Porter Church Professor of Engineering, professor of
>astronomy and vice provost for physical sciences and engineering. "Studying
>the moons and learning about their interactions with the rings will help us
>understand how the moons formed and perhaps how the Saturn system formed."
>The D ring is another example of the rings' changeability. Cassini's images
>of the outer part of that ring show what look like a series of closely
>spaced ringlets. "We spent a long time trying to figure out what the heck
>this was," said Matt Hedman, a Cornell postdoctoral researcher and Cassini
>team member. "It turns out that what's really going on is, wherever you see
>a bright spot on the near side, you see a dark spot on the far side, and
>vice versa. That pattern is something you might expect if the ring were
>For clues about how the ring came to be warped, researchers looked back to
>a view of the rings taken by the Hubble Space Telescope (HST) in 1995 and
>found the same pattern -- with one difference: Cassini's images have the
>ripples spaced 30 kilometers (18 miles) apart; the HST images show them 60
>The likely explanation, said Hedman, is that the ring was tilted slightly
>out of Saturn's equatorial plane at some point in the past, possibly by a
>passing meteoroid. Because Saturn is not a perfect sphere (it's a little
>squashed) the inner parts of a canted flat disk around it will twist faster
>than the outer parts, leading the ring in transition to be a warped,
>corrugated spiral -- like the top of a twirled soft ice cream cone.
>Mathematical models support the hypothesis, even predicting independently
>the rate at which the ripples move. "As the thing twists more and more,
>these ripples will get closer together. It actually works numerically,"
>In the course of Cassini's mission, the ripples have moved closer by
>another 2-3 kilometers. Using the model to unwind the spiral back in time,
>researchers trace the probable impact back to 1984 -- just a few years
>"This is the first time we've truly seen the entire ring system," said
>Burns. "It's an eerily beautiful sight, and one that's evolving right in
>front of our eyes."
>The Cassini-Huygens mission is a cooperative project of NASA, the European
>Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory
>(JPL), a division of the California Institute of Technology, manages the
>mission for NASA.
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>Ithaca, NY 14850
>cunews at cornell.edu
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