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Saturn: the "Ringed Beauty" and His Moons
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Prometheus_and_Pandora-PIA07544.jpgPrometheus and Pandora56 visiteSaturn's moons Prometheus and Pandora are captured here in a single image taken from less than 1° above the dark side of Saturn's Rings. Pandora is on the right and Prometheus is on the left. Prometheus is 102 Km (63 miles) across, while Pandora is 84 Km (52 miles) across.
The two moons are separated by about 69.000 Km (about 43.000 miles) in this view. The F-Ring, extending farthest to the right, contains a great deal of fine, icy material that is more the size of dust than the boulders thought to comprise the dense B-Ring.
These tiny particles are particularly bright from this viewing geometry, especially at right near the ansa, or edge.
At left of center, a couple of ringlets within the Encke gap (325 Km or 200 miles wide) can also be easily seen due to their fine dust-sized material. The other dark features in the Rings are density waves and bending waves. The image was taken in visible light from a mean distance of 1,85 MKM from the moons.
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Prometheus_and_the_Rings.jpgPrometheus and the Rings57 visiteCaption NASA originale:"What do Saturn's Rings look like from the other side? From Earth, we usually see Saturn's Rings from the same side of the ring-plane that the Sun illuminates them. Geometrically, in the above picture taken in April by the Cassini Spacecraft, the Sun is behind the camera but on the other side of the ring-plane. Such a vantage point gives a breathtaking views of the most splendid ring system in the Solar System. Strangely, the Rings have similarities to a photographic negative of a front view. For example, the dark band in the middle is actually the normally bright B-Ring. The Ring brightness as recorded from different angles indicates ring thickness and particle density of ring particles. Images like these are also interesting for what they do not show: such as the spokes. The unexpected shadowy regions once recorded by the Voyager missions when they passed Saturn in the early '80s are not, so far, being seen by Cassini. Extra credit: Can you spot the small moon (Prometheus)?
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Prometheus~0.jpgThe "Rise" of Prometheus...61 visiteCaption NASA:"What is that dark streak below Prometheus? Although it may look like a shadow or a trail blazed by sweeping up material, computer simulations indicate that the dark streak is better understood as an empty path pulled away by the gravity of Saturn's small moon. The particles don't follow Prometheus so much as glide sideways past where Prometheus used to be. One dark Streamer is created during each pass of Prometheus through the F-Ring that it shepherds.
The Streamers were unpredicted and first discovered in 2004 on HR images taken by the Cassini Spacecraft orbiting Saturn.
Close inspection of the Surface of Prometheus itself in the above image shows interesting structure and craters.
The Cassini Spacecraft arrived at Saturn in 2004 and, as it continues to function well, is now expected to continue to send back data and images from the distant ringed world until 2017".MareKromium
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Propeller-PIA11672-a.jpgGiant "Propeller" in the A-Ring (CTX Frame)60 visiteAn unusually large "Propeller" feature is detected just beyond the Encke Gap in this Cassini image of Saturn’s outer A-Ring taken a couple days after the Planet’s August 2009 Equinox.
The unique geometry of Equinox has thrown into relief small moonlets within the Rings and the structures they create around them. Propeller-like features, a few kilometers long, centered on and created by the action of small embedded moonlets only about 100 meters across, were discovered early in the mission (see also PIA07792 and PIA07790).
These previous findings constituted the first recognition of the presence in Saturn’s Rings of bodies bigger than the largest ring particles (about 10 meters, or 30 feet, across) but smaller than the 8-Km-wide (about 5-mile-wide) ring moon, Daphnis, in the outer A-Ring.
From the 350-Km (about 220-mile) length of the shadow cast by this 130-Km-long (about 80-mile-long) Propeller, the heights of these features above the Ring-Plane have been measured to reach about 200 meters (650 feet), indicating the moonlet responsible for the Propeller in this image is likely to be 400 meters (1300 feet) across.
A previously released early-Equinox image also had revealed a moonlet in the outer B-Ring about 400 meters (1300 feet) across (see PIA11665).MareKromium
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Propeller-PIA11672-b.jpgGiant "Propeller" in the A-Ring (EDM)54 visiteIt has since become a growing realization resulting from Cassini’s exploration of Saturn that the objects forming Saturn’s Rings very likely span the full spectrum of sizes, from the smallest dust-sized ring particles to the ring-moons like Daphnis and 29-Km-wide (18-mile-wide) Pan - a significant advance in divining the origin of Saturn’s Rings.
The novel illumination geometry that accompanies equinox lowers the Sun’s angle to the Ring-Plane, significantly darkens the Rings and causes out-of-plane structures to cast long shadows across the Rings. (The Rings have been brightened in this image to enhance visibility)
These scenes are possible only during the few months before and after Saturn’s Equinox which occurs only once in about 15 Earth years.
This view looks toward the Northern Side of the Rings from about 20° above the Ring-Plane.
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on Aug. 13, 2009.
This view was acquired at a distance of approx. 1,2 MKM (about 746.000 miles) from Saturn and at a Sun-Saturn-Spacecraft, or Phase, Angle of 87°.
Image scale is roughly 7 Km (about 4,5 miles) per pixel.MareKromium
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Propeller-PIA12790-1.jpgSaturnian "Propeller": Earhart54 visiteA propeller-shaped structure created by an unseen moon is brightly illuminated on the Sunlit Side of Saturn's Rings in this image obtained by NASA's Cassini Spacecraft.
The moon, which is too small to be seen, is at the center of the Propeller Structure visible in the upper left of the image, near the Encke Gap of the A-Ring. The A-Ring is the outermost of Saturn's Main Rings.
The moon is likely about 1 Km (a little moere than half a mile) across. Disturbed ring material to the upper left and lower right of the moon reflects Sunlight brightly and appears like a white airplane propeller.
Several density waves are also visible in the Ring. A spiral density wave is a spiral-shaped accumulation of particles that tightly winds many times around the Planet. It is the result of gravitational tugs by individual moons whose orbits are in resonance with the particles' orbits at a specific distance from Saturn.
A Propeller's appearance changes with viewing geometry, and this image shows the way a Propeller looks when viewed from the sunlit side of the Rings. Contrasts can reverse when the structure is observed on the dark side of the Rings: for example, the bright structure of this Propeller corresponds to the dark portion at the center of the propeller seen in PIA12791 which was imaged from the unilluminated side of the Rings.
This image is part of a growing catalogue of "Propeller Moons" that, despite being too small to be seen, enhance their visibility by creating larger disturbances in the surrounding fabric of Saturn's Rings. Cassini scientists now have tracked several of these individual Propeller Moons embedded in Saturn's disk over several years.
These images are important because they represent the first time scientists have been able to track the orbits of objects in space that are embedded in a disk of material. Continued monitoring of these objects may lead to direct observations of the interaction between a disk of material and embedded moons. Such interactions help scientists understand fundamental principles of how Solar Systems formed from disks of matter. Indeed, Cassini scientists have seen changes in the orbits of these moons, although they don't yet know exactly what causes these changes.
Imaging scientists nicknamed the Propeller shown here "Earhart" after the early American aviatrix Amelia Earhart. The Propeller Structure is about 5 Km (a little more than 3 miles) in the radial dimension (the dimension moving outward from Saturn which is far out of frame to the lower right of this image). It is about 60 Km (approx. 35 miles) in the azimuthal (longitudinal) dimension.
This same Propeller can be seen casting a shadow around the time of the Planet's Equinox in PIA11672. See PIA07791 and PIA07792 to learn more about Propeller shapes and to see smaller Propellers.
Scale in the original image was about 2 Km (about 1,3 miles) per pixel. The image has been rotated and contrast-enhanced to aid visibility.
This view looks toward the Southern, sunlit side of the Rings from about 81° below the Ring-Plane. The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on April 11, 2008. The view was obtained at a distance of approx. 364.000 Km (such as about 226.000 miles) from Saturn and at a Sun-Saturn-Spacecraft, or Phase, Angle of 82°.MareKromium
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Propeller-PIA12790-2.jpgSaturnian "Propeller": Blériot57 visiteNASA's Cassini Spacecraft captured a Propeller-shaped Disturbance in one of Saturn's Rings created by a moon that is too small to be seen here.
The moon, likely about 1 Km (a little more than half a mile) across, is invisible at the center of the image. However, it is larger than many other "Propeller" moons and has cleared ring material from the dark wing-like structures to its left and right in the image. Disturbed ring material closer to the moon reflects Sunlight brightly and appears like a white airplane propeller. This Propeller appears in the A-Ring, which is the outermost of Saturn's Main Rings.
Taken in 2006, this image is part of a growing catalogue of "Propeller Moons" that, despite being too small to be seen, enhance their visibility by creating larger disturbances in the surrounding fabric of Saturn's Rings. Cassini scientists now have tracked several of these individual Propeller Moons embedded in Saturn's disk over several years.
These images are important because they represent the first time scientists have been able to track the orbits of objects in space that are embedded in a disk of material. Continued monitoring of these objects may lead to direct observations of the interaction between a disk of material and embedded moons. Such interactions help scientists understand fundamental principles of how Solar Systems formed from disks of matter. Indeed, Cassini scientists have seen changes in the orbits of these moons, although they don't yet know exactly what causes these changes.
Imaging scientists nicknamed the Propeller shown here "Bleriot" after a French aviator named Louis Bleriot.
The Propeller's structure is about 5 Km (approx. 3 miles) in the radial dimension -- the dimension moving directly outward from Saturn. The dark wings appear approx. 1100 Km (about 700 miles) in the azimuthal (longitudinal) dimension, while the central propeller structure is roughly 110 Km (about 70 miles) long.
See PIA12792 to watch a movie of "Bleriot." PIA11672 shows the giant propeller "Earhart" named after another aviator, Amelia Earhart. See PIA07791 and PIA07792 to learn more about propeller shapes and to see smaller propellers.
This image has been re-projected so that orbiting material moves to the right and Saturn is down. The Propeller was seen at the edge of the camera's field of view when the image was taken, so some data were missing; the blank space at the top of the image was filled in with a gray color. Scale in the original image was approx. 2 Km (about 1,3 miles) per pixel. Image scale in this re-projected view is about 1 Km (a little more than half a mile) per pixel.
This view looks toward the Southern, Sunlit side of the Rings from about 30° below the Ring-Plane. The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on Dec. 15, 2006. The view was acquired at a distance of approx. 463.000 Km (about 288.000 miles) from Saturn and at a Sun-Saturn-Spacecraft, or Phase, Angle of 15°.MareKromium
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Propellers-000-PIA07792.jpgThe "Propellers" of the Rings (1) - HR55 visiteThis collection of 3 Cassini images provides context for understanding the location and scale of some "propeller-shaped features" observed within Saturn's A-Ring.
Careful analysis of the HR images taken by Cassini's cameras as the spacecraft slipped into Saturn orbit revealed the 4 faint, propeller-shaped double-streaks in an otherwise bland part of the mid A-Ring. Imaging scientists believe the "propellers" provide the first direct observation of the dynamical effects of moonlets which are approx. 100 mt (such as about 300 feet) in diameter.
The propeller moonlets represent a so far unseen size-class of particles orbiting within the Rings.
The 2nd panel provides broad context within the Rings, and shows the B-Ring, the Cassini Division, the A-Ring and the F-Ring. Image scale in the radial, or outward from Saturn, direction is about 45 Km (about 28 miles) per pixel; because the Rings are viewed at an angle, the image scale in the longitudinal - or circumferential - direction is several times greater.
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Propellers-001-PIA07792.jpgThe "Propellers" of the Rings (2) - HR54 visiteThis image is a closer view of the A-Ring, showing the radial locations where "Propeller Features" were spotted. The view is approx. 1.800 Km across (such as about 1.100 miles), from top to bottom, and includes a large density wave at the bottom (caused by the moons Janus and Epimetheus), as well as two smaller density waves.
The footprints of the Propellers are between density waves, in bland, quiescent regions of the Ring.
The Propellers appear as double dashes in the two close-up discovery images and they have been circled. The unseen moonlets, each roughly the size of a football field, lie in the center of each structure. These two images were taken during Saturn orbit insertion on July 1, 2004, and are presented here at one-half scale. Resolution in the original images was 52 mt (about 171 feet) per pixel.
The horizontal lines in the image represent electronic noise and do not correspond to any actual Ring features.
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Propellers-002-PIA07790.jpgThe "Propellers" of the Rings (3) - HR54 visiteThe Propellers are about 5 Km (approx. 3 miles) long from tip to tip, and the radial offset (the "leading" dash is slightly closer to Saturn) is about 300 mt (about 1000 feet).
The Propellers structures are unchanged as they orbit around Saturn.
In that way, they are much like the wave pattern that trails after a speedboat as it skims across a smooth lake. Such a pattern is hard to discern in a choppy sea (---> mare increspato). In much the same way, scientists think other effects may be preventing Cassini from seeing the Propellers except in very bland parts of the Rings.
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Propellers-003-PIA07791.jpgThe "Propellers" of the Rings (4) - HR (detail mgnf)54 visiteThis magnified view illustrates the general orientation of the Propellers in Saturn's Rings, as they orbit around the Planet.
The two dashes of the Propeller are oriented in the direction of orbital motion. The "leading" dash is also slightly closer to Saturn; this "radial offset" is about 300 mt (about 1000 feet). The unseen moonlet lies in the center of the structure.
The grainy appearance of the image is due to magnification and the fact that the Propellers are very faint - just visible above the level of the back-ground noise. Consequently, the image enhancement procedures used to create this detail mgnf, have also enhanced the noise.
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Pseudo-UFO.gifLook: a "Pseudo-UFO"!!! (GIF-Movie - credits: Dr Gianluigi Barca)54 visiteGrazie all'ottimo Lavoro del Dr Gigi Barca, ecco che possiamo illustrarVi in maniera precisa, puntuale ed adeguata un nuovo (e triste) esempio di (dis)informazione becera e malfatta: molti Appassionati, infatti, spinti dalle solite (in un sol tempo sensazionalistiche e clamorosamente superficiali) dichiarazioni di qualche "pseudo-ricercatore", starebbero osservando lo "sbuffo" (!) lasciato da un'astronave che si allontana dall'Anello "G" di Saturno.
Ebbene NO: SBAGLIATO! A costo di risultare - purtroppo è così... - "antipatici" a molti, dobbiamo fare ancora una volta i de-bunkers. "Sbuffo" di plasma-energia (alla Star-Trek)?
No, cari Amici. Proprio no.
Si tratta del solito effetto prismatico che si produce quando la luce proveniente da un corpo molto luminoso (ivi, ipotizziamo, Rhea od Encelado - o, comunque, una luna di Saturno, e questo lo capirebbe anche uno studente di Astronomia alle primissime armi...) passa attraverso la porzione esterna delle ottiche che lo riprendono.
Osservare l'Universo è bellissimo; cercare il Mistero nell'Universo, si sa, fa parte della Natura dell'Uomo.
Così come fa pure parte della Natura Umana (per lo meno: della Natura di alcuni...) lo "sparare scemenze" senza neppure pensare un attimo a ciò che si guarda ed a ciò che si dice.
Peccato. Peccato perchè è sempre facendo così che si crea ignoranza e delusione. Certo, "smontando", "razionalizzando" e "spiegando" - come tentiamo di fare noi - non si matura molta "audience" ma, detto sinceramente, di un'audience che poggia sul "niente", in fondo, a noi non importa nulla.
Un grande complimento al Dr Barca per l'ennesimo OTTIMO Lavoro!
MareKromium
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