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| Piú viste - Saturn: the "Ringed Beauty" and His Moons |
Tethys-PIA09766.jpgThe "Dark Belt" of Tethys123 visiteCaption NASA:"Around the Equator on its Leading Side, Tethys wears a band of slightly darker surface material. Cassini Imaging Scientists suspect that the darkened region may represent an area of less contaminated ice with differently sized grains than the material at higher latitudes on either side of the band.
Lit terrain seen here is on the Saturn-facing side of Tethys. North is up. Part of the great canyon system Ithaca Chasma can be seen near the eastern limb in this frame-filling view.
The image was taken with the Cassini spacecraft narrow-angle camera on Sept. 30, 2007 using a spectral filter sensitive to wavelengths of infrared light centered at 930 nanometers. The view was acquired at a distance of approx. 186.000 Km (such as about 116.000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 62°.
Image scale is roughly 1 Km (about 0,6 mile) per pixel".MareKromium
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Helene-PCF-LXTT-IPF.jpgHelene (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team) 123 visiteHelene (one of the many moons of the Giant Gas-Planet Saturn) was discovered by the French Astronomers Pierre Laques and Jean Lecacheux in 1980, from ground-based observations carried out at the "Pic du Midi" Observatory; at first, it was designated S/1980 S 6. Afterwards, in 1988, it was officially named Helene (after Helen of Troy, who was the granddaughter of Cronus - Saturn -, according to Greek mythology).
This small moon (we are talking about a Celestial Body, mostly made of Ice and Rock, which is approx. 30 Km across) is also designated as Saturn XII, a number which it received in 1982, under the designation of Dione B (since Helene is co-orbital with Dione and located in its Leading Lagrangian Point - L4). Helene is one of 4 (four) known so-called "Trojan Moons" of the Saturnian System.
For sake of clarity, please remember that:
A) the Saturnian System contains two sets of Trojan Moons. Both Tethys and Dione have, in fact, two Trojan Moons: Telesto and Calypso, which are located in Tethys' L4 and L5 Lagrangian Points, respectively, and Helene with Polydeuces, which are located in Dione's L4 and L5 Lagrangian Points, respectively;
B) in Astronomy, a co-orbital configuration refers to 2 (two) or more Celestial Objects - such as Asteroids, Moons, or even Planets - that orbit at the same, or very similar, distance from their Parent Object as well as from each other. In other words, they are in a 1:1 (one-to-one) mean Motion Resonance;
C) there are several Classes of co-orbital Objects, depending on their Point of Libration. The most common and best-known Class, is the Trojan, which librate around one of the two stable Lagrangian Points (also known as "Trojan Points"), L4 and L5, 60° ahead of, and behind, the larger Parent Body, respectively. Another class is the so-called "Horseshoe Orbit", in which the Celestial co-Orbital Objects librate around 180° from the larger Parent Body. Objects librating around 0° are called, instead, "Quasi-Satellites".
When two co-Orbital Objects are of similar masses (and thus they exert a non-negligible - i.e.: meaningful - Gravitational Influence on each other) they can even arrive to exchange their orbits. For instance, talking about Janus and Epimetheus, we know that the Timing and Magnitude of their Momenta exchange in such a way that the two moons actually "trade" their orbits, while never getting closer (---> approaching each other) than about 10.000 Km. The exchange takes place about once every 4 years; the last close approaches occurred on January 21, 2006, and in 2010, when Janus' Orbital Radius increased by ~20 Km, while Epimetheus' decreased by ~80 Km. However, Janus' orbit is less affected by the swop, because Janus itself is about 4 times more massive than Epimetheus. As far as it is currently known, this "arrangement" is unique in the Solar System.
As we already said hereabove, Helene was initially observed from Earth in 1980 but, when the NASA - Voyager Probes passed through the Saturnian System, they allowed us to get much closer views of it. Afterwards, the NASA - Cassini Spacecraft, which went into orbit around Saturn in 2004, provided still better views and allowed more in-depth analysis of this moon, including views of its Surface under different lighting conditions. Although conventional Impact Craters and Hills do appear, this image also shows Terrain that looks unusually smooth and streaked. Some of the closest images of Helene to date are from the Cassini Spacecraft's 1800 Km Fly-By that occurred on March 3, 2010, and another very successful imaging sequence which was obtained in June 2011.
There have been many other approaches over the course of the Cassini mission, and future Fly-Bys may yield additional data.This frame has been colorized in Natural Colors (such as the colors that a perfect human eye would actually perceive if someone were onboard the NASA - Cassini Spacecraft and then looked outside, towards the Saturnian moon Helene), by using an original technique created - and, in time, dramatically emproved - by the Lunar Explorer Italia Team.MareKromium
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EnceladusFountains-PIA07762.gifThe "Fountains" of Enceladus122 visiteJets of icy particles burst from Enceladus in this GIF sequence of 4 images taken on Nov. 27, 2005. The sensational discovery of active eruptions on a third outer Solar System body (after Jupiter's moon, Io, and Neptune's moon, Triton) is one of the great highlights of the Cassini mission.
Images taken in January 2005, appeared to show the plume originating from the fractured South Polar Region of Enceladus, but the visible plume was only slightly brighter than the background noise in the image because the lighting geometry was not suitable to reveal the true details of the feature. This potential sighting, in addition to the detection of the icy particles in the plume by other Cassini instruments, prompted imaging scientists to target Enceladus again with exposures designed to confirm the validity of the earlier plume sighting.
The new views show individual jets, or plume sources, that contribute to the plume with much greater visibility than the earlier images.
The full plume towers over the 505-kilometer-wide (314-mile) moon, and is at least as tall as the moon's diameter.
The four, 10-second exposures were taken over the course of about 36 minutes at approximately 12-minute intervals. Enceladus rotates about 7.5 degrees in longitude over the course of the frames, and most of the observed changes in the appearances of the jets are likely due to changes in the viewing geometry. However, some of the changes may be due to actual variation in the flow from the jets on a time scale of tens of minutes.
Additionally, the shift of the sources seen here should provide information about their location in front of and behind the visible limb (edge) of Enceladus.
These images were obtained using the Cassini spacecraft narrow-angle camera at distances between 144,350 and 149,520 kilometers (89,695 and 92,907 miles) from Enceladus and at a phase angle of about 161 degrees. Image scale is about 900 meters (2,950 feet) per pixel on Enceladus.
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Enceladus-PIA10354.jpgStellar Data on "Enceladus Plume"121 visiteCaption NASA:"New structure, density and composition measurements of Enceladus' water plume were obtained when the Cassini Spacecraft's Ultraviolet Imaging Spectrograph observed the star "Zeta Orionis" pass behind the plume Oct. 24, 2007, as seen in this frame.
Changes in the starlight as it dimmed while passing through the plume allowed the spectrograph to identify the plume's physical and chemical composition.
The spectrograph detected 4 high-density gas streams composed of Water Vapor. The density of the Water Vapor is twice that of the broad plume of gas that surrounds each jet.
This measurement confirms the theoretical analysis performed prior to the flyby that showed it was safe for Cassini to fly very closely past Enceladus, even through part of the plume, during the March 12, 2008 flyby".MareKromium
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UnusualObject-N00122114-4.jpgUnusually-looking "Object" in the Space of Saturn (edm n. 2, by Lorenzo Leone)121 visitenessun commentoMareKromium
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Enceladus-PIA12719-PCF-LXTT.jpgEnceladus (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)121 visiteCaption NASA:"Two sources of light reveal the dramatic Surface of Saturn's moon Enceladus in this Cassini image in which geologic features give the appearance of the leathery skin of an elephant.
Geologically young and (relatively) smooth Terrain in the Southern and Middle Latitudes gives way to older, Cratered Terrain in the Northern Latitudes of the moon.
Sunlight illuminates the right of the image, and light reflected off Saturn ("Saturnshine") dimly illuminates the left. This view looks toward the Leading Hemisphere of Enceladus.
North on Enceladus is up.
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on April 7, 2010. The view was obtained at a distance of approx. 198.000 Km (such as about 123.000 miles) from Enceladus and at a Sun-Enceladus-Spacecraft, or Phase, Angle of 92°.
Image scale is roughly 1 Km (3300 feet) per pixel".MareKromium
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AF-A new Streak in the Sky-N00015685.jpgA new "Big Streak" in the Sky of Saturn120 visiteImmagine ripresa dalla Sonda Cassini/Huygens il giorno 30 Agosto 2004 e ricevuta dal Mission Control il giorno successivo. C'è qualcosa che è passato (o sta passando...) accanto alla Sonda, mentre questa riprende un'immagine dello Spazio di Saturno.
E' un semplice riflesso?
Forse no.
Vi abbiamo proposto delle immagini che riprendono "riflessi" (o qualcosa di simile ad essi) e l'effetto che si vede è molto diverso.
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AAB-The Sky of Saturn before the 2nd Streak.jpgSaturn's Sky just before the 2nd "Streak" - W00000827119 visiteIl giorno 6 Agosto 2004 accade nuovamente qualcosa di affascinante ed inspiegabile: una delle fotocamere di cui la Sonda Cassini/Huygens è dotata si sta riposizionando verso un nuovo obbiettivo e, nel farlo, riprende immagini "random" dello Spazio di Saturno, ossia senza puntare ad un oggetto determinato (questo in accordo a quanto riportano le fonti ufficiali). Questo è il frame che precede l'apparizione della nuova "striscia di luce": si vedono alcune stelle e tutto sembra normale.
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The_Rings-N00154409-416-EB-LXTT.gifThe Beautiful Rings of Saturn (a GIF-Movie by Elisabetta Bonora - Lunexit Team)119 visitenessun commentoMareKromium
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Saturn-PIA09009-PCF-LXTT-IPF.jpgSaturnian Cloud Bands (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunar Explorer Italia/Italian Planetary Foundation)119 visiteCaption NASA:"The Cassini Spacecraft spies smooth, sometimes wavy, contours in the banded East-West flowing clouds of Saturn. This view shows clouds in Saturn's Northern Mid-Latitudes.
The image was taken using a spectral filter sensitive to wavelengths of infrared light centered at 727 nanometers. The view was obtained with the Cassini spacecraft narrow-angle camera on July 8, 2007 at a distance of approx. 2,9 MKM (about 1,8 MMs) from Saturn.
Image scale is roughly 34 Km (about 21 miles) per pixel".
Un nuovo passo in avanti per la Colorizzazione Naturale Assoluta creata da Lunar Explorer Italia: ora, infatti, inizieremo la rivalutazione (in senso di analisi cromatica) dei frames CASSINI e, quindi, la ricolorizzazione di Saturno. Ecco il primo "nato" di questa nuova serie.MareKromium
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The_Rings-N00124202.jpgAnother UFO in the Space of Saturn?117 visiteCaption NASA:"N00124202.jpg was taken on November 16, 2008 and received on Earth November 17, 2008. The camera was pointing toward SATURN-RINGS that, at the time, were approx. 384.802 Km away, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated".MareKromium
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Aurora Borealis on Saturn (HST).jpgAurora Borealis on Saturn (HST)116 visiteUn'Aurora Boreale sul Polo Sud di Saturno: forse la cosa non sorprenderà nessuno e l'immagine che Vi proponiamo, infatti, è piuttosto vecchia (siamo nel Gennaio 1998).
Siamo tuttavia certi che solo pochi Appassionati e Ricercatori sanno che, solo sino a pochissimi anni fa, la Comunità Scientifica Mondiale supponeva che le Aurore Boreali (che Hubble ha fotografato mentre si scatenavano su tutti i Giganti Gassosi) fossero un fenomeno 'tipicamente terrestre'.
E così chissà quante altre fenomenologie che riteniamo essere 'tipicamente terrestri' sono, in realtà, una prerogativa comune all'intero Universo...
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