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The_Rings-PIA11142.jpgSaturn's Rings: the whole System66 visitenessun commentoMareKromium
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The_Rings-PIA11144.jpgSpokes (natural - but enhanced - colors; credits: Lunar Explorer Italia)100 visiteCaption NASA:"Dark Spokes dance around Saturn's B-Ring in this image taken with Cassini's wide-angle camera.
As Saturn nears Equinox (which will occur in August 2009) and the Sun angle on the Ring-Plane decreases, Spokes become common sights in Cassini images, just as they were in Voyager images. The Planet's orbital period is 29,5 years, so Saturn has nearly made one complete trip around the Sun since the flybys of the two Voyager Spacecraft (1980 and 1981), allowing Cassini to closely match Voyager's viewing geometry.
The Spokes appear dark against Saturn's B-Ring at low phase angles because the particles within them scatter light more efficiently in the forward direction (meaning away from Cassini) than the surrounding larger ring particles. In the opposite viewing geometry, at high phase angles, spokes appear bright relative to surrounding ring particles (See PIA07807).
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The_RingsPIA11142.jpgSaturn's Rings: the whole System (natural colors; credits: NASA)57 visiteCaption NASA:"Details of Saturn's icy Rings are visible in this sweeping view from Cassini of the Planet's glorious Ring System.
This natural color mosaic, taken from 10° below the illuminated side of the Rings, shows, from left to right, radially outward from Saturn, the C-Ring (with its Colombo and Maxwell Gaps); the B-Ring and the Cassini Division beyond, with the intervening Huygens Gap; the A-Ring (with its Encke and Keeler Gaps); and, on the far right, the narrow F-Ring. The total span covers approx. 65.700 Km (such as about 40.800 miles).
Although it is too faint to be seen here, the D-Ring is located just to the left of the C-Ring.
It is interesting to compare this view with PIA08389, which shows the unilluminated side of the Rings. The difference in brightness of the B-Ring relative to the other Rings is striking. When illuminated directly by the Sun, the B-Ring appears brighter than the adjacent A and C-Rings; however, when viewing the unlit side of the B-Ring, the A and C-Rings appear brighter.
This phenomenon occurs because the density of the B-Ring is greater than that of the A or C-Rings.
The mosaic was constructed from 45 narrow-angle-camera images — 15 separate sets of red, green and blue images — taken over the course of about four hours, as Cassini scanned across the Rings. The images in this view were obtained by NASA's Cassini Spacecraft on Nov. 26, 2008, at a distance of approx. 1,1 MKM (such as about 700.000 miles) from Saturn and at a Phase Angle of 28°.
Image scale in the radial (horizontal) direction is about 7 Km (4,3 miles) per pixel".MareKromium
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