Saturn: the "Ringed Beauty" and His Moons
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Saturn-PIA07695.jpgDark Saturn, Bright Rings53 visiteCaption originale:"The Cassini spacecraft looked toward the darkened night side of Saturn to capture the eerie glow of the Rings, which, not being blocked by the Planet's bulk, remained brilliant in full Sunlight.
The image was taken in visible light with the Cassini spacecraft wide-angle camera on Dec. 24, 2005, at a distance of approx. 286.000 Km (roughly 178.000 miles) from Saturn.
The image scale is about 13 Km (approx. 8 miles) per pixel".
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Saturn-PIA07731-1.jpgSpokes (1)55 visiteAfter much anticipation, Cassini has finally spotted the elusive "spokes" in Saturn's Rings.
"Spokes" are the ghostly Radial Markings discovered in the Rings by NASA's Voyager spacecraft 25 years ago. Since that time, Spokes had been seen in images taken by NASA's Hubble Space Telescope but had not, until now, been seen by Cassini.
These three images, taken over a span of 27', show a few faint, narrow Spokes in the outer B-Ring. The Spokes are about 3500 Km (2200 miles) long and about 100 Km wide (60 miles). The motion of the Spokes here is from left to right.
They are seen just prior to disappearing into the Planet's shadow on the Rings.
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Saturn-PIA07731-2.jpgSpokes (2)53 visiteAt the bottom left corner of the 1 st and 2nd image, the bright inner edge of the A-Ring is visible. Continuing radially inward (or toward Saturn) are several bands that lie within the Cassini Division, bounded by the bright outer edge of the B-Ring. The rounded shadow of Saturn cuts across the Rings in the image at right.
Cassini's first sighting of Spokes occurs on the unilluminated side of the Rings, in the same region in which they were seen during the Voyager flybys. Although the most familiar Voyager images of spokes showed them on the sunlit side of the Rings, spokes also were seen on the unilluminated side.
In Voyager images, when Spokes were seen at low phase angles, they appeared dark; when seen at high phase angles, they appeared bright. The Spokes seen here are viewed by Cassini at a very high phase angle, which is about 145° at the center of each image.
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Saturn-PIA07731-3.jpgSpokes (3)53 visiteImaging team members will be studying the new Spoke images and will maintain their vigil for additional Spoke sightings.
These images were taken using the clear filters on Cassini's Wide-Angle Camera on Sept. 5, 2005, at a mean distance of 318.000 Km (198.000 miles) from Saturn. The radial scale on the Rings (the image scale at the center of each image) is about 17 Km (about 11 miles) per pixel.
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Saturn-PIA07772.jpgThe Light Colors of Saturn53 visiteFew sights in the Solar System are more strikingly beautiful than softly hued Saturn embraced by the shadows of its stately Rings. The gas Planet's subtle Northward gradation from gold to azure is a striking visual effect that scientists don't fully understand.
Current thinking says that it may be related to seasonal influences, tied to the cold temperatures in the Northern (winter) Hemisphere. Despite Cassini's revelations, Saturn remains a world of mystery. Currently, the Rings' shadows shield the mid-northern latitudes from the harshest of the Sun's rays. As Saturn travels around the Sun in its 29-year orbit, the shadows will narrow and head southward, eventually blanketing the opposite hemisphere.
Images taken with blue, green and red spectral filters were used to create this color view, which approximates the scene as it would appear to the human eye. The view was brightened to enhance detail visible in the rings and within their shadows.
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Saturn-PIA08130.jpgIs that a "Vertical Relief"?!?73 visiteOccasional views like this one, showing "vertical relief" in Saturn's cloud tops, help the streamers and swirls of gas seem more like a three dimensional structure than a smooth surface. As on Saturn's solid moons, vertical relief is easiest to view near the Terminator, and makes visible the shading of deeper cloud tops by high altitude bands.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 23, 2006, at a distance of approx. 2.7 MKM (about 1,7 MMs) from Saturn. Resolution in the original image was 16 Km (about 10 miles) per pixel. The image has been magnified by a factor of two and contrast-enhanced to aid visibility.
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Saturn-PIA08131.jpgThe "Little Eye" of Saturn53 visiteCaption NASA originale:"This interesting vortex in Saturn's atmosphere is surrounded by a halo of bright clouds that extend away toward the East and West. Storms like this one seem to be bright at all wavelengths at which Cassini observes them.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 24, 2006, at a distance of approx. 2,9 MKM (about 1,8 MMs) from Saturn. The image scale is roughly 17 Km (approx. 11 mi) per pixel".
Nota: le grandi tempeste di Saturno (come quelle di Giove), se abbiamo capito bene quello che dice la NASA, appaiono "brillanti" su tutte le lunghezze d'onda. Attenzione: noi sappiamo che le nuvole, in generale, riflettono molto bene la luce del Sole e che quindi (come ci insegna il caso di Venere) aumentano l'albedo visuale di qualsiasi corpo celeste il quale ne sia dotato. Tuttavia noi pensiamo che la luminosità a cui la NASA abbia fatto riferimento in questo caso NON sia quella che abbiamo appena cercato di esprimere (e cioè una maggiore/migliore riflessione della luce in arrivo dal Sole): a nostro parere quanto detto dalla NASA in sede di commento al frame in oggetto potrebbe e dovrebbe significare che le tempeste che occorrono sui Giganti Gassosi (forse anche Urano e Nettuno; certamente Giove e Saturno) esprimono un certo quantitativo di energia il quale viene colto anche sotto forma di luce (che poi si tratti di semplici lampi o di qualcosa di diverso e di più complesso, non lo sappiamo).
Per ora...
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Saturn-PIA08140.jpgRestless Atmosphere (1)55 visiteThis atmosphere close-up shows bright clouds in Saturn's Northern Hemisphere being sheared apart. The clouds at the bottom of the image are tilted and stretched because the wind at those lower latitudes is moving much faster to the East than the wind at the higher latitudes near the top of the image, hence the shear.
This appearance suggests that these bright eddies are passive tracers of the atmosphere's motion - they appear, probably as a result of upwelling due to convection from below, and then they are sheared apart.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 16, 2006, at a distance of approximately 3,3 MKM (about 2 MMs) from Saturn. The image scale is roughly 19 Km (about 12 miles) per pixel.
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Saturn-PIA08141.jpgRestless Atmosphere (2)53 visiteSaturn's atmosphere comes alive with a multitude of dark vortices swirling through the Southern Hemisphere.
Vortices are long-lived features that are part of the general circulation of Saturn's atmosphere. Vortices are thought to be caused by the shear between Eastward- and Westward-flowing jets - the alternating bands flowing past each other in the atmosphere. The vortices can last for months or years and probably grow by merging with other vortices until a few dominate a particular zone of wind shear between two jets. The vortex at upper right is one of the largest vortices on Saturn.
The image was taken with the Cassini spacecraft narrow-angle camera on Feb. 16, 2006 at a distance of approximately 3,2 MKM (about 2 MMs) from Saturn. The image scale is about 19 Km (approx. 12 miles) per pixel.
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Saturn-PIA08142.jpgSaturnian Super-Storm "Alley"!66 visiteStorm Alley's latest, greatest resident, the recent lightning-producing storm seen by the Cassini spacecraft and Earth-based observers churns away. Turbulent eddies to the West (left) of the storm indicate that it is moving eastward relative to the westward-flowing winds at this latitude on Saturn.
Scientists gave the nickname "Storm Alley" to the area around 35° South Latitude because of the large amount of activity seen there from the beginning of the Cassini spacecraft's approach to Saturn in early 2004. The Region has spawned two large and powerful storms since the Cassini spacecraft began observations.
The image was taken with the Cassini spacecraft narrow-angle camera on Feb. 16, 2006, using a filter sensitive to wavelengths of infrared light centered at 750 nanometers, and at a distance of approx. 3,2 MKM (such as about 2 MMs) from Saturn. The image scale is roughly 19 Km (about 12 miles) per pixel.
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Saturn-PIA08143.jpgThe texture of the Rings and Northern Regions of Saturn53 visiteShadows drape Saturn's Northern Hemisphere, providing a different kind of look at prominent features in the Rings. From the lower left corner upward, the visible features are: the shadow of the outer B-Ring, followed by the wide, bright Cassini Division, then the A-Ring with the embedded thin, bright Encke Gap and finally the dark, narrow, F-Ring.
The image was taken with the Cassini spacecraft narrow-angle camera on Feb. 18, 2006, using a filter sensitive to wavelengths of infrared light centered at 750 nnmts, and at a distance of approx. 2,8 MKM (such as about 1,7 MMs) from Saturn. The image scale is roughly 16 Km (about 10 miles) per pixel.
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Saturn-PIA08151.jpgSaturn's Southern Restlesness53 visiteThis view of high Southern Latitudes on Saturn shows very linear clouds at top, usually indicative of stable prevailing winds, and two turbulent, swirling features farther South. It is possible that these features merged some time after this image was taken.
The image was taken with the Cassini spacecraft narrow-angle camera on March 6, 2006, using a filter sensitive to wavelengths of infrared light centered at 750 nnmts. The image was acquired at a distance of approximately 2,8 MKM (about 1,8 MMs) from Saturn. The image scale is approx. 16 Km (roughly 10 miles) per pixel.
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