| Piú viste - Saturn: the "Ringed Beauty" and His Moons |
The Rings-2-PIA07872.jpgThe "Rings": the most spectacular view ever seen!57 visiteSpecially designed Cassini orbits place Earth and Cassini on opposite sides of Saturn's rings, a geometry known as "occultation". Cassini conducted the 1st radio occultation observation of Saturn's Rings on May 3, 2005.
Three simultaneous radio signals of 0,94; 3,6, and 13 cm wavelengths (Ka-, X-, and S-bands) were sent from Cassini through the rings to Earth. The observed change of each signal as Cassini moved behind the Rings provided a profile of the distribution of ring material as a function of distance from Saturn, or an optical depth profile.
This simulated image was constructed from the measured optical depth profiles. It depicts the observed ring structure at about 10 Km in resolution. Color is used to represent information about ring particle sizes in different regions based on the measured effects of the 3 radio signals. Shades of purple, primarily over most of the inner ring (ring B) and the inner portion of the next ring (ring A), indicate regions where there is a lack of particles less than 5 centimeters (about 2 inches) in diameter. Green and blue shades indicate regions where there are particles of sizes smaller than 5 centimeters (2 inches) and 1 centimeter (less than one third of an inch), respectively, primarily in outer ring A and within most of ring C. From other evidence in the radio observations, all ring regions appear to be populated by a broad range of particle size distribution that extends to boulder sizes (several to many meters or yards across).
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Saturn-W00006821.jpgSpark in the Dark! (possible Anomaly)57 visiteCassini sta viaggiando nel cono d'ombra generato da Saturno e quindi, se il 'volto di Saturno' sta guardando il Sole, noi possiamo pure dire che Cassini è 'alle spalle' del Gigante Anellato.
Ciò premesso, riusciamo comunque a vedere una porzione dell'Anello F (ancora illuminato da Sole e davvero caratteristico ed inconfondibile per i suoi 'clumps'!) sull'estrema Dx dell'immagine mentre, proprio al centro del frame, distinguiamo chiaramente un corpo luminoso sferico e svariati altri puntini luminosi e svariati graffi. Sui 'puntini luminosi' ed i 'graffi', la nostra esperienza in campo di fotografia astronomica e spaziale ci dice che si tratta di semplici photo-artifacts. Il punto luminoso centrale, invece, secondo noi NON lo è.
Ora, dato che stiamo guardando in una regione immersa nell'ombra di Saturno (e dunque nel buio), quel punto - se effettivamente NON è un photo-artifact - NON può neppure essere una delle Lune Saturniane!
E allora che cos'è?
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The Rings-N00034622.jpgSunshine and stars, through the F-Ring!57 visiteUn'immagine davvero molto bella e suggestiva; inutili altri commenti.
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Saturn-PIA06658.jpgSunlit South...57 visiteCaption NASA originale:"This poetic wide-angle camera view of Saturn reveals several small, dark storms in the southern latitudes, where storm activity has been prevalent since before Cassini arrived in orbit.
Also notable here is the semi-transparent C-Ring, which is visible against the backdrop of the planet.
The image was taken in visible light with the Cassini spacecraft wide-angle camera on April 23, 2005, through a filter sensitive to wavelengths of infrared light centered at 1028 nnmts and at a distance of approx. 2,4 MKM (about 1,5 MMs) from Saturn. The image scale is 142 Km (approx. 88 miles) per pixel".
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Atlas-PIA06659.jpgAtlas: Ring-Master or Prisoner of the Rings?57 visiteCaption NASA originale:"Saturn's little moon Atlas orbits Saturn between the outer edge of the A-Ring and the fascinating, twisted, F-Ring. This image just barely resolves the disk of Atlas and also shows some of the knotted structure for which the F-Ring is known. Atlas is 32 Km (about 20 miles) across. The bright outer edge of the A-Ring is overexposed here, but farther down the image several bright ring features can be seen. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 25, 2005, at a distance of approx. 2, 4 MKM (about 1,5 MMs) from Atlas and at a Sun-Atlas-Spacecraft, or phase, angle of 60°. Resolution in the original image was 14 Km (approx. 9 miles) per pixel".
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The Rings-PIA07512.jpgClose-up on the Rings!57 visiteCaption NASA originale:"This amazing close-up of Saturn's Rings reveals their incredible variety. In some regions there are wavelike structures, while in other places the Rings' structure appears to be more chaotic.
This image shows (from top to bottom) the A-Ring with the Encke gap, the Cassini Division, the B-Ring and the C-Ring.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 26, 2005, at a distance of approx. 2,3 MKM (such as 1,5 MMs) from Saturn. The image scale is 14 Km (approx. 8 miles) per pixel".
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Hyperion-N00035398.jpgHyperion, from about 202.000 Km (3)57 visiteE' davvero semplice 'caos' quell'estrema complessità che caratterizza il moto di Iperione, così come la struttura di alcuni lontanissimi 'oggetti' di origine forse stellare (quali i Buchi Neri, i Quasar ed i Pulsar etc.), oppure anche questi 'movimenti' e queste 'strutture', così lontane dal nostro pensare e sapere, obbediscono a delle Logiche Maggiori che, oggi, non riusciamo neppure ad immaginare?
Questa piccola diversione filosofica non è, a nostro modo di vedere, un inutile esercizio dialettico: noi siamo sempre più convinti, infatti, che la disarmante 'semplicità' con cui la Scienza Consolidata cerca di spiegare alcuni fenomeni, unita all'estrema - ed inutile - complessità con cui Essa cerca di spiegarne altri, sìano entrambe espressioni di un notevole imbarazzo di fondo il quale si manifesta davanti ad una realtà piuttosto evidente.
Quale? La realtà che l'Universo è ancora molto lontano non solo dall'essere compreso nei suoi meccanismi quanto, addirittura, dall'essere anche solo immaginato...
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TheRings-PIA07522.jpgFour versions of the "F-Ring"57 visiteCaption NASA originale:"This montage of 4 images of Saturn's knotted F-Ring shows different locations around the Ring itself. Even though all the images were taken within a few hours of each other, there is remarkable variation in the structure of the F-Ring at these four locations.
For example, the number of ring strands differs from image to image and in some images, kinks are clearly visible in the F-Ring, while other regions appear more smooth.
Astronomers believe that the structure of Saturn's F-Ring is governed by its shepherding moons, Prometheus and Pandora. The F-Ring's appearance is expected to vary depending on how recently a ring section has encountered each moon and how close the moon came to the ring".
Nota: nel primo quadro (in alto a Sx) c'è qualcosa, posto proprio al di sopra del 'nodo' centrale visibile sull'intreccio più luminoso dell'Anello F, che sembra un 'filamento' o, comunque, un oggetto estraneo all'Anello F stesso, ma reale (NON crediamo che sia un photo-artifact). Cos'è?
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Pandora-PIA07530.jpgPandora: the closest view so far!57 visiteCaption NASA originale:"This is one of Cassini's closest views to date of Saturn's F-Ring shepherd moon Pandora. At least one crater is visible on the surface of this moon, which is thought to be an icy rubble pile, loosely bound together by gravity. Pandora is 84 Km across.
Several of Saturn's Ring moons, including Pandora, show elongated, oval-like shapes with their long axes oriented along the moon-Saturn line. In this view, Cassini is looking at the side of Pandora facing away from Saturn. The image shows the moon's leading hemisphere (although, as mentioned, Pandora is not actually round). To the right, much of the moon's surface is in shadow. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 20, 2005, at a distance of approx. 346.000 Km from Pandora and at a Sun-Pandora-spacecraft, or phase, angle of 21°".
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Epimetheus-PIA07531.jpgEpimetheus57 visiteCaption NASA originale:"Cassini continues to survey the small worlds that orbit near Saturn's Rings, capturing this view of Epimetheus.
The moon's lumpy, irregular topography can be seen here, along with several impact craters. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 20, 2005, at a distance of about 345.000 Km from Epimetheus and at a phase angle of 26°.
Resolution in the original image was 2 Km per pixel.
The view was also magnified by a factor of two and contrast-enhanced to aid visibility of the moon's surface".
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Hyperion-anagliph-PIA06244.jpgStereo-Hyperion! (from about 176.000 Km)57 visiteCaption NASA originale:"Saturn's moon Hyperion pops into view in this stereo anaglyph (or 3D view) created from Cassini images. Images taken from slightly different viewing angles allow construction of such stereo views, which are helpful in interpreting the moon's irregular shape.
Hyperion's unusual dimensions are 164 by 130 by 107 Km (such as 102 by 81 by 66 miles).
Craters are visible on the moon's surface down to the limit of resolution in this image, about 1 Km (0,6 mile) per pixel. The fresh appearance of most of these craters, combined with their high spatial density, makes Hyperion look something like a sponge. The moon's spongy-looking exterior is an interesting coincidence, as Hyperion's density seems to indicate that it is porous and much of its interior is filled with voids.
Dark material is concentrated in the bottoms of many craters visible here, perhaps resulting from the down slope movement of material, combined with sublimation of brighter ice".
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Enceladus-N00037076.jpgGood-bye Enceladus! (1)57 visiteEncelado è ormai una splendida "falce" nel cielo e questo ci fa capire che la Sonda Cassini ha ormai superato il suo punto di maggior vicinanza a questo mondo di ghiaccio e di neve, i cui caratteri superficiali terranno impegnati Scienziati e Ricercatori per mesi (o forse anni...).
Cassini si allontana rapidamente ed ora si sta proiettando, ancora una volta, verso lo Spazio di Saturno.
Ma ritornerà...
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