Saturn: the "Ringed Beauty" and His Moons
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Rings-PIA06588.jpgThe "rings" and a "string" of Moons...55 visiteCaption NASA originale:"Moons visible in this image: Mimas (398 Km, or 247 miles across) at right, Pandora (84 Km, or 52 miles across) near center and Janus (181 Km, or 113 miles across) in the lower left corner. Mimas' orbit inclination of 1,6° relative to Saturn's equator is enough to make it appear as if it orbits just beyond the F-Ring when viewed from this vantage point of 5° below the Rings. In fact, it is 34.000 Km (such as approx. 21.000 miles) more distant than Janus".
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Rings-PIA06616.jpgDistances...57 visiteCaption NASA originale:"This sweeping view from Cassini gives a sense of the awesome scale of the planet's disk-like ring system, which stretches many thousands of kilometers into the distance. The shepherd moon Prometheus maintains a lonely sojourn with the thin, outer F-Ring.
A notable brightening of the F-Ring material is visible ahead of Prometheus in its orbit, near the right side of this image.
The view was obtained in visible light with the Cassini spacecraft narrow-angle camera on Feb. 18, 2005, at a distance of approximately 1 MKM (approx. 621.000 miles) from Prometheus and at a phase angle of 105°. The image scale is 6 Km per pixel".
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Rings-PIA07556.jpgThe "Opposition Effect"58 visiteCaption NASA originale:"The "opposition effect" can be seen in this image of Saturn's B ring. The bright spot occurs where the angle between the spacecraft, the Sun and the Rings is near zero.
Studies of the Opposition Effect on Saturn's Rings may help scientists constrain some of the properties of the Ring particles, such as their sizes and spatial distribution.
The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 26, 2005, at a distance of approximately 478.000 Km (about 297.000 miles) from Saturn. The image scale is 3 Km (about 2 miles) per pixel".
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Rings-PIA07579.jpgPandora, Prometheus and the F-Ring55 visiteOriginal NASA caption:"From just outside the faint edge of Saturn's F-Ring, the moon Pandora keeps watch over her fine-grained flock.
The outer flanks of the F-Ring region are populated by ice particles approaching the size of the particles comprising smoke!
As a shepherd moon, Pandora helps her cohort Prometheus confine and shape the main F-Ring (Pandora is 84 Km (such as 52 miles) across while Prometheus is 102 Km (such as 63 miles) wide and orbits interior to the F-Ring.
The small knot seen attached to the core is one of several that Cassini scientists are eyeing as they attempt to distinguish "embedded moons" from "transient clumps of material".
The image was taken with the Cassini spacecraft narrow-angle camera on Aug. 2, 2005, using a filter sensitive to wavelengths of infrared light centered at 930 nnmts at a distance of approx. 610.000 Km (such as about 379.000 miles) from Pandora and at a Sun-Pandora-spacecraft, or phase, angle of 146°. Image scale is 4 Km per pixel".
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Rings-PIA07654.jpgCrescent Enceladus and Crescent Rings57 visiteSunlight reflects off the bright, frozen surfaces of the billions and billions of particles comprising Saturn's Rings to brighten the Planet's Southern Skies.
The particles in Saturn's Rings are each too small to be seen by Cassini in this image but, if they could, each would look like the bright reflective crescent of Enceladus seen here, with each reflecting sunlight onto the Southern Hemisphere of the Planet.
The image was taken in polarized infrared light with Cassini's wide-angle camera on Nov. 2, 2005, at a distance of approx. 1,7 MKM (1,1 MMs) from Saturn and at a phase angle of 119°. The image scale is roughly 104 Km (about 65 miles) per pixel.
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Rings-PIA07716.jpgCan the "clumps" in the Rings be the TSP (Transient Saturnian Phoenomena)?55 visite"Scientists have long suspected that small moons hiding among Saturn's Rings strands might be producing some of the unusual structure observed in the F-Ring. While the shepherd moon Prometheus is the main culprit behind the strange behavior of Saturn's F-Ring, it cannot explain all observed features. The current dilemma facing scientists is that Cassini is detecting extended objects like those pictured here - that may be either solid moons or just loose clumps of particles within the Ring. This montage of 4 enhanced Cassini narrow-angle camera images shows bright clump-like features at different locations within the F-Ring.
Two objects in particular, provisionally named S/2004 S3 and S/2004 S6, have been repeatedly observed by Cassini over the past 13,5 months and 8,5 months, respectively. The orbits for these 2 objects have not yet been precisely determined, in part because perturbations from other nearby moons make the orbits of objects in this region complicated. Thus, scientists cannot be completely confident at the present time if they in fact have observed new sightings of S3 and S6, or additional transient clumps.
The upper two images show features that may be S6. From previous observations, S6 appears to have an orbit that crosses that of the main F ring. This unexpected behavior currently is a subject of great interest to ring scientists.
The upper left image was taken on June 21, 2005, and shows an object in the outer ringlets of the F ring. The radial (or lengthwise) extent of the feature is approximately 2,000 kilometers (1,200 miles). The radial resolution on the ring is about 13 kilometers (8 miles) per pixel.
The image at the upper right was taken on June 29, 2005, and shows a bright feature within the F ring's inner ringlets. The radial extent of the feature seen here is about 2,000 kilometers (1,200 miles); the radial resolution is 36 kilometers (22 miles).
The image at the lower left was taken on August 2, 2005, and shows a feature that may be S3. S3 has been found to have an orbital path that is tightly aligned with that of the main F ring. The radial resolution in the image is 3.5 kilometers (2.2 miles) per pixel.
The lower right image was taken on April 13, 2005, and has a radial resolution of 7 kilometers (4 miles) per pixel. This object does not appear to be either S3 or S6.
Structures like knots and clumps within the F ring often are transient, appearing and then disappearing within months. Repeated observation of the objects seen in this region hopefully will give scientists firm evidence about whether these features are actual moons that disturb the material around them or perhaps the short-lived products of interactions between the F ring and larger moons such as Prometheus.
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Rings-PIA07718.jpgArcs in the G-Ring54 visiteOriginal NASA caption:"This sequence of images shows a faint arc of material in Saturn's G-Ring, a tenuous ring outside the main Ring System. These images were each taken about 45' apart. During this time, the arc (slightly brighter than the Ring itself) moves around the outer edge of the Ring. The arc is visible on the lower part of the Ring in the first image, just beneath the ansa (or outer edge). In the second image the arc is easily seen on the outer edge and then faintly just above the outer edge in the third image.
What makes this part of the G-Ring brighter than other parts is not clear. However, the existence of this arc might hold clues about how this ring was formed and where the material which makes up this ring comes from. These 3 images were taken in polarized near-infrared light using the Cassini spacecraft narrow-angle camera on May 24, 2005, at a distance of approx. 1,7 MKM (about 1,1 MMs) from Saturn. Resolution in the original images was about 97 Km per pixel".
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Rings-PIA08241.jpgDifferent Light, Different Brightness, Different Motion...66 visiteCaption NASA:"This close-up view of the inner A-Ring shows intriguing variations in brightness along the direction of the Ring motion - from top to bottom. Close examination reveals dark regions that appear to widen and then narrow, and thin bright regions that disappear altogether.
Variations in brightness are to be expected in the direction of increasing orbital distance from Saturn, but variations along the azimuthal (or circumferential) direction are unusual, as they should be smoothed out quickly by ring particle motion.
Note: the faint "doughnut" left of center and the dark area in the lower right corner are imaging artifacts.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 23, 2006 at a distance of approx. 285.000 Km (about 177.000 miles) from Saturn. Image scale is about 1 Km (0,6 mile) per pixel".
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Rings-W00004066.jpgOverexposed Rings and a lonely moon...54 visiteImmagine ampiamente sovraesposta (ma non per questo meno suggestiva) della parte più esterna degli Anelli di Saturno, con l'aggiunta di una luna solitaria (Encelado?) che, grazie anche alla lunga esposizione operata dalla camera della Sonda, brilla come un faro nel buio dello spazio intorno al secondo Gigante del Sistema Solare.
Una bellissima "istantanea dallo Spazio", a nostro parere...
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RingsStructure-2-PIA03550.jpgThe "Rings' Structure"57 visiteSaturn's Rings make up an enormous, complex structure. From edge-to-edge, the Ring System would not even fit in the distance between Earth and the Moon. The 7 main rings are labeled in the order in which they were discovered. From the planet outward, they are D, C, B, A, F, G and E. The D-Ring is very faint and closest to Saturn. The main Rings are A, B and C. The outermost Ring, easily seen with Earth-based telescopes, is the A-Ring. The Cassini Division is the largest gap in the Rings and separates the B from the A-Ring. Just outside the A-Ring is the narrow F-Ring, shepherded by tiny moons Pandora and Prometheus. Beyond that are 2 much fainter Rings named G and E. Saturn's diffuse E-Ring is the largest planetary ring in our Solar System, extending from Mimas' orbit to Titan's orbit, about 1 MKM.
The particles in Saturn's rings are composed primarily of water ice and range in size from microns to tens of meters. The rings show a tremendous amount of structure on all scales; some of this structure is related to gravitational interactions with Saturn's many moons, but much of it remains unexplained. One moonlet, Pan, actually orbits inside the A ring in a 330-kilometer-wide (200-mile) gap called the Encke Gap. The main rings (A, B and C) are less than 100 meters (300 feet) thick in most places, compared to their radial extent of 62,120 kilometers (38,600 miles). The main rings are much younger than the age of the solar system, perhaps only a few hundred million years old. They may have formed from the breakup of one of Saturn's moons or from a comet or meteor that was torn apart by Saturn's gravity.
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SA-Night On Saturn.jpgNight On Saturn56 visitenessun commento
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SATURN by VOYAGER - 1980.jpgSaturn from the Voyager79 visitenessun commento
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