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| Piú votate - Uranus and His Moons |
Uranus-familyportrait-PIA01975_modest.jpgThe 5 major moons of Uranus59 visiteThis "family portrait" of Uranus' 5 largest moons was compiled from images sent back Jan. 20, 1986, by Voyager 2 spacecraft. The pictures were taken through a clear filter from distances of 5 to 6,1 MKM (3,1 to 3.8 MMs). In this comparison, we see the relative sizes and relativities of the satellites. From left, in order of increasing distance from the planet, they are Miranda, Ariel, Umbriel, Titania and Oberon. The 2 largest, Oberon and Titania, are about half the size of Earth's Moon, or roughly, 1.600 Km (1.000 miles) in diameter. Miranda, smallest of the 5, has about one-quarter to one-third the diameter. Even in these distant views, the satellites exhibit distinct differences in appearance. On average, Oberon and Titania reflect about 20% of the sunlight, Umbriel about 12%, Ariel and Miranda about 30%. Ariel shows the largest contrast on its surface, with the brightest areas about 25%. All five satellites show only slight color variations on their surfaces, with their average color being very nearly gray. The best views of the satellites will be obtained Jan. 24, the day of closest approach.
(5 voti)
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VC-Belinda-V2.jpgBelinda - Voyager 254 visiteEd ora una carrellata relativa ad alcune delle Lune "minori" di Urano. La maggior parte di esse è stata scoperta ex-post, cioè analizzando le immagini mandateci alcuni anni fa dai nostri Messaggeri inviati ai confini del Sistema Solare: le Sonde Voyager 1 e 2. Si tratta di mondi assai minuscoli, dalle forme irregolari, probabilmente non originari del Sistema di Urano, ma "catturati" dal Gigante Gassoso in epoche più o meno remote. Forse, queste Lune minori, sono delle "comete mancate" o forse sono frammenti, schegge di corpi celesti più grandi entrati in collisione quando il Sistema Solare era ancora - relativamente - "giovane". Qualunque sia la verità (che, probabilmente, non conosceremo mai), noi Vi offriamo le immagini che abbiamo raccolto in giro per la Rete e desideriamo ringraziare l'Ing. Calvin J. Hamilton, creatore e curatore del bellissimo Sito conosciuto come "Views of the Solar System".
(5 voti)
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Oberon-V2-PIA01352_modest.jpgOberon, from far away...55 visiteOberon, la Luna Maggiore di Urano: la più esterna e la più grande.
In questa immagine (a differenza della precedente che, ad oggi, è la migliore disponibile!) la Sonda Voyager 2 era ancora troppo lontana da Oberon per catturarne i segreti (la fotografia è stata scattata da una distanza di circa 2.700.000 Km!), ma alcuni dettagli delle sua superficie (i quali peraltro evidenziano una scarsissima albedo: Oberon, in effetti, riflette - in media - circa il 20% della luce solare che riceve) appaiono già con una certa chiarezza.
(5 voti)
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VA-Uranus_ Rings-V2-PIA01977_modest.jpgUranus' Rings (1)55 visiteEcco gli Anelli di Urano, dei quali si è sovente parlato, ma senza mai approfondire l'argomento in maniera particolare.
Noi Vi offriamo 3 istantanee provenienti dalla Sonda Voyager 2 e relative a questa ennesima Meraviglia del Cosmo. Non ci sono segni evidenti di anomalie e le immagini, occorre dirlo, non sono di grandissima qualità. Tuttavia, in attesa di nuovi passaggi ravvicinati accanto a questo strano Gigante Gassoso (passaggi, purtroppo, non previsti a breve...), noi guardiamo ancora al passato ed a ciò che abbiamo raccolto negli anni trascorsi.
Il valore storico di queste fotografie è indiscutibile; quello scientifico può essere meglio compreso confrontandole con le immagini ad Alta Definizione degli Anelli di Saturno che ci arrivano - possiamo dire "quotidianamente" - dalla Sonda NASA-ESA Cassini-Huygens.
(5 voti)
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Titania-PIA01978-PCF-LXTT-IPF.jpgOn the Limb of Titania (Possible Absolute Natural Colors; credits for the additional process. and color. Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)82 visiteLike their semi-divine namesakes, Dione's twin Impact Craters Romulus and Remus (just above-right of the center) stand together while Dido, the larger Impact Crater showing a magnificent and impressive Central Peak, lies to the South/East, on the lower left Limb of Dione and almost half-way on top of the Terminator. The lit Terrain seen here is on the Saturn-facing Hemisphere of Dione and North is up.
The image was taken in Visible Light with the NASA - Cassini Spacecraft Narrow-Angle Camera on April 28, 2013. The view was obtained at a distance of approximately 870.000 miles (such as a little more than 1,4 Million KiloMeters) from Dione and at a Sun-Dione-Cassini Spacecraft, or Phase, Angle of 77°. Image scale is roughly 5 miles (a little more than 8 Km) per pixel.
This frame (which is an Original NASA - Cassini Spacecraft b/w frame published on the NASA - Planetary Photojournal with the ID n. PIA 17126) has been additionally processed, contrast enhanced, magnified to aid visibility of the Surface details and then colorized, according to an educated guess carried out by Dr Paolo C. Fienga/LXTT/IPF, in what they should be its Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Cassini Spacecraft and then looked outside, towards the Saturnian moon Dione), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Dione, each having a different Albedo (---> Reflectivity) and Chemical Composition.
Note: it is possible (but we, as IPF, have no way to be one-hundred-percent sure of such a circumstance), that the actual luminosity of Dione - as it is in this frame - would appear, to an average human eye, a little bit lower than it has been shown (or, better yet: interpreted) here.MareKromium
(4 voti)
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Miranda-PIA00042-PCF-LXTT-IPF.jpgMiranda's Southern Hemisphere (Possible Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)76 visiteThis image-mosaic of the Uranian moon Miranda was taken by the NASA - Voyager 2 Spacecraft on January 24, 1986, from a distance of approx. 147.000 Km (such as about 91.287 miles). This image-mosaic was constructed from images taken through the Spacecraft's Narrow-Angle Camera's Green, Violet and UltraViolet Filters.
Miranda, just about 480 Km (such as approx. 299 miles) across, is the smallest of Uranus' five Major natural satellites. Miranda's Regional Geologic Provinces are shown very well in this view of its Southern Hemisphere, imaged at a resolution of roughly 2,7 Km (such as 1,67 miles) per pixel. The dark- and bright-Banded Region with its curvilinear traces, covers about half of the frame. Higher-resolution pictures taken some time later showed many Fault Valleys and Ridges, all parallel to these "Bands". Near the Terminator Line (on the right - Dx), another system of Ridges and Valleys abuts the Banded Terrain; furthermore, many Impact Craters pockmark the Surface of Miranda all over this Region. The largest of these Craters are about 30 Km (approx. 18,63 miles) in diameter and many more of them lie in the range of 5 to 10 Km (such as from 3,1 to 6,2 miles) in diameter.
This frame (which is an Original NASA - Voyager 2 Spacecraft Natural Color image-mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 00042) has been additionally processed, contrast enhanced, magnified to aid visibility of the Surface details and then re-colorized, according to an educated guess carried out by Dr Paolo C. Fienga/LXTT/IPF, in what they should be its Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 2 Spacecraft and then looked outside, towards the Uranian moon Miranda), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Miranda, each having a different Albedo (---> Reflectivity) and Chemical Composition.
Note: it is possible (but we, as IPF, have no way to be one-hundred-percent sure of such a circumstance), that the actual luminosity of Miranda - as it is in this frame - would appear, to an average human eye, a little bit lower than it has been shown (or, better yet: interpreted) here.MareKromium
(4 voti)
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Titania-PIA01979-PCF-LXTT-IPF.jpgTitania (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)100 visiteCaption NASA:"Voyager 2 obtained this full-disk view of Uranus' moon Titania in the early morning hours of Jan. 24, 1986, from a distance of about 500.000 Km (approx. 300.000 miles). Many circular depressions -- probably impact craters -- are visible in this clear-filter image returned by the Voyager narrow-angle camera.
Other bright spots are distinguished by radiating rays and are probably halo craters that mark relatively more recent impacts. Even more interesting are Linear Troughs (right) that are probably Fault Canyons (Tectonic Fractures). The Troughs break the crust in two directions, an indication of some tectonic extension of Titania's crust. These features indicate that this icy satellite has a dynamic, active interior. Titania is about 1600 Km (approx. 1000 mi) in diameter; the resolution of this image is about 9 Km (approx. 6 mi) per pixel". MareKromium
(4 voti)
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Miranda-PIA00042-PCF-LXTT.jpgMiranda (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)204 visitenessun commentoMareKromium
(4 voti)
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Miranda-PIA00044-Verona_Rupes-PCF-LXTT.jpgVerona Rupes (Super Close-Up - Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)203 visitenessun commentoMareKromium
(4 voti)
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UMBRIEL-vg2-SV.jpgUmbriel's most prominent Surface Features: Skynd and Wunda Craters (Natural Colors; credits: NASA)54 visiteThe surface of Umbriel is an ancient one.
A collection of impact craters of various sizes was found to saturate the landscape. As Voyager 2 drew closer, became clear that most or all of the bright features are related to craters. On the Terminator, one can see 2 interesting craters.
One, Skynd, has a bright Central Peak. The other, Wunda, at the top of the image, has a bright rim and no apparent Central Peak. This is the best color image obtained by Voyager 2.MareKromium
(4 voti)
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UMBRIEL-vg2_p29502-Wunda.jpgUmbriel's extremely unusual surface feature: Wunda Crater (Natural Colors; credits: NASA)54 visiteHere is a closeup systhesis from all the close-ups of Wunda Crater.
It is hard to tell if the craters dug up the bright material, or if they had something to do with the impacts. Maybe it was derived from eruptions or melting caused by impacts.
Or maybe they are some sort of frost left over from impacts.
This issue may not be resolved until another spacecraft observes Umbriel. Here is the best view of Wunda that can be generated with the available data.MareKromium
(4 voti)
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Uranus-Neptune-HST3_.JPGUranus and Neptune, from HST (Natural Colors and Enhanced Natural Colors; credits: NASA)54 visitenessun commentoMareKromium
(4 voti)
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