| Piú viste - Uranus and His Moons |
Uranus-HST-CJH.jpgUranus, from HST103 visitenessun commento
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Miranda-vg2_2684617-A.jpgThe beautiful "Verona Rupes" from a different angle (context image)100 visitenessun commento
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UMBRIEL-PIA00040-PCF-LXTT-IPF.jpgUmbriel (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)100 visiteThe Southern Hemisphere of the Uranian moon Umbriel displays heavy Cratering in this NASA - Voyager 2 image, taken on January 24, 1986, at a distance of approx. 557.000 Km (such as a little less than 346.000 miles) from the Surface of the moon. This frame, taken through the Clear-Filter of Voyager's Narrow-Angle Camera, is the most detailed image of Umbriel that we have, with a resolution of about 10 Km (such as 6,21 miles) per picture element.
Umbriel is the darkest of Uranus' larger moons and the one that appears to have experienced the lowest level of Geological Activity. It has a diameter of about 1200 Km (a little more than 745 miles) and its Surface reflects only 16% of the light that receives; in the latter respect, Umbriel is similar to the Lunar Highland Areas of our own Moon. Umbriel, as we wrote herebefore, is heavily cratered, but it lacks the numerous Bright-Ray Craters that are commonly seen on the other large Uranian Natural Satellites; this fact, among other things, results in a relatively uniform Surface Albedo (---> Reflectivity).
The prominent Impact Crater visible on the Terminator (at about 11 o'clock of Umbriel's disk) is approx. 110 Km (such as 68,3 miles) across and it shows a really bright Central Peak. On the other hand, the strangest Surface Feature visible in this image (on the Limb of Umbriel, right at 12 o'clock of the disk) is a curious-looking Bright Ring which represents the most reflective area seen on Umbriel itself. The Bright Ring is about 140 Km (approx. 87 miles) in diameter and it lies near the moon's Equator. The nature of the Bright Ring is unknown, although it might be a very large Frost Deposit, perhaps associated with (located on top and near) the Rim of a huge Impact Cater. The few white spots that can be barely seen against the black background are not stars, but just just image artifacts, due to 'noise' in the data received on Earth.
This frame (which is the Original NASA - Voyager 2 b/w image published on the NASA - Planetary Photojournal with the ID n. PIA 00040) has been additionally processed and then colorized, according to an educated guess carried out by Dr Paolo C. Fienga (LXTT-IPF), in 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 Neptunian moon Triton), 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 Triton, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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Miranda-V2-PIA01980_modest.jpgMiranda: a funny shaped Moon99 visiteIn questa seconda immagine di Miranda risulta ben visibile una vastissima depressione situata in prossimità del suo Polo Nord la quale potrebbe aver avuto origine a seguito di un impatto con un altro corpo celeste di notevoli dimensioni.
Una luna che ha "sofferto", dunque, e la cui storia risale - molto probabilmente - alle stesse origini del nostro Sistema Solare, quando gli impatti - specie nella sua "periferia" - avvenivano con una frequenza di gran lunga maggiore rispetto a quanto accade ai giorni nostri.
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VI-Puck-V2.jpgPuck - Voyager 299 visitenessun commento
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Uranus-familyportrait-PIA01975_modest.jpgThe 5 major moons of Uranus97 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.
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VF-Cressida, Ophoelia, Portia.jpgCressida, Ophoelia and Portia - Voyager 296 visiteUn piccolissimo commento (forse abbastanza scontato): noi non sappiamo chi, fisicamente, abbia dato i nomi a queste Lune Minori di Urano ma, certamente, si trattava di un appassionato lettore di Sir William Shakespeare.
Non credete?!?...
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Oberon-vg2_2683623-1.jpgOberon's "Peak"96 visiteEd ecco il più intrigante rilievo superficiale di Oberon: una montagna (la cui forma, per gli appassionati di "Space Oddities", ricorda una specie di piramide) di circa 6000 mt di altezza che spicca, molto chiaramente, sul bordo di questa affascinante e lontano Corpo Celeste.
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VE-Caliban.jpgCaliban95 visiteUna "Luna Minore" di Urano, Calibano, persa fra le stelle ed individuabile solo grazie alla "cerchiatura" bianca inserita in questa (comunque molto bella) immagine.
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VG-Desdemona-V2.jpgDesdemona - Voyager 293 visitenessun commento
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AB-Ariel-vg2_2684535.jpgCrescent Ariel (HR)93 visitenessun commento
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Uranus-Voyager2-PIA00369.jpgUranus Cloud Movement93 visiteTime-lapse Voyager 2 images of Uranus show the movement of 2 small, bright, streaky clouds - the first such features ever seen on the Planet. The clouds were detected in this series of orange-filtered images taken Jan. 14, 1986, over a 4.6-hour interval (from top to bottom). At the time, the spacecraft was about 12,9 MKM (about 8 MMs) from the Planet, whose pole of rotation is near the center of each disk. Uranus, which is tipped on its side with respect to the other planets, is rotating in a counterclockwise direction, as are the 2 clouds seen here as bright streaks.
(The occasional donut-shaped features that show up are shadows cast by dust in the camera optics. The processing necessary to bring out the faint features on the Planet also brings out these camera blemishes.) The larger of the 2 clouds is at a latitude of 33°; the smaller cloud, seen faintly in the 3 lower images, lies at 26° (a lower latitude and hence closer to the limb). Their counterclockwise periods of rotation are 16.2 and 16.9 hours, respectively. This difference implies that the lower-latitude feature is lagging behind the higher-latitude feature at a speed of almost 100 meters per second (220 mph). Latitudinal bands are also visible in these images. The faint bands, more numerous now than in previous Voyager images from longer range, are concentric with the pole of rotation -- that is, they circle the planet in lines of constant latitude.MareKromium
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