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| Piú viste - Uranus and His Moons |
Uranus from Keck Obs..jpgUranus from Keck Observatory112 visiteCaption NASA originale:"These sharp views of tilted gas giant Uranus show dramatic details of the planet's atmosphere and ring system. The remarkable ground-based images were made using a near-infrared camera and the Keck Adaptive Optics system to reduce the blurring effects of Earth's atmosphere. Recorded in July 2004, the pictures show two sides of Uranus. In both, high, white cloud features are seen mostly in the northern (right) hemisphere, with medium level cloud bands in green and lower level clouds in blue. The artificial color scheme lends a deep reddish tint to the otherwise faint rings. Because of the severe tilt of its rotational axis, seasons on Uranus are extreme and last nearly 21 Earth years on the distant planet. Uranus is now slowly approaching its southern autumnal equinox - the beginning of fall in the southern hemisphere - in 2007".
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VI-Puck-HR-V2.JPGPuck (possible Natural Colors; credits: Lunar Explorer Italia)112 visitenessun commentoMareKromium
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Oberon-PIA01352-PCF-LXTT-IPF.jpgIcy Oberon (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunar Explorer Italia/Italian Planetary Foundation)111 visiteUranus' outermost and largest moon, Oberon, can be very well seen in this NASA - Voyager 2 frame which was obtained January, 22, 1986, from a distance of approx. 2,77 Million KiloMeters (such as a little more than 1,72 Million Miles). The Clear-Filter Image, shuttered by the Voyager's Narrow-Angle Camera, shows us that Oberon displays several distinct Highly Reflective (---> High-Albedo) "Patches" of its Surface which also show - and this circumstance still sounds kind of strange/unusual - very Low-Albedo Centers. Some of the bright Patches are suggestive of Radial Patterns that could represent the visible consequence of powerful Impact Events which occurred on a basically Ice-rich Surface (in other words, we may be looking at Rayed Impact Craters that formed - were excavated - on an extremely hard and frozen Surface) .
On average, Oberon reflects (in all directions) only about 20% (twenty-percent) of the Incident Sunlight and that fact makes it Celestial Body with a (relatively) Low Albedo. The moon is about 1600 Km (such as approx. 993,6 miles) in diameter; the resolution of this image is roughly 51 Km (such as about 31,67 miles) per pixel. This frame was taken 2 (two) days before Voyager's 2 Closest Approach to Oberon (at which point the Spacecraft flew-by Oberon at a distance of approx. 471.000 Km - such as about 292.491 miles - from its frozen Surface).
This frame (which is an Original NASA - Voyager 2 Spacecraft Natural Color image published on the NASA - Planetary Photojournal with the ID n. PIA 01352) 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 Oberon), 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 Oberon, each having a different Albedo (---> Reflectivity) and Chemical Composition.
Note 1: 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 Oberon - 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.
Note 2: the "squared" feature visible at about 4 o'clock of Oberon's disk (almost on the Limb of the moon and right on the Terminator Line), is just an original image defect.MareKromium
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Miranda-PIA00140.jpgMiranda, from approx. 31.000 Km110 visiteCaption NASA originale:"This Voyager 2 image of Miranda was taken Jan 24, 1986, from a distance of about 31.000 Km (19.000 miles), shortly before the spacecraft's closest approach to the Uranian moon. The HR of 600 meters (2.000 feet) reveals a bewildering variety of fractures, grooves and craters, as well as features of different albedos (reflectancea). This clear-filter, narrow-angle view encompasses areas of older, heavily cratered terrain with a wide variety of forms. The grooves and troughs reach depths of a few Km (or miles) and expose materials of different albedos. The great variety of directions of fractures and troughs, and the different densities of impact craters on them, signify a long, complex geologic evolution of this satellite".
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Uranus from Voyager2.jpgUranus from Voyager 2109 visiteL'immagine che state osservando venne scattata dalla Sonda Voyager 2 nel 1986. Fu grazie a questa Sonda (l'unica - ad oggi - che sia mai passata nelle vicinanze del Pianeta) che gli Scienziati riuscirono a catturare qualche dettaglio del Sistema di Urano il quale, al pari dei Sistemi di Nettuno, Giove e Saturno, evidenzia l'esistenza di anelli intorno al Pianeta (ma molto sottili e deboli) ed un elevato quantitativo di lune (5 maggiori ed una quindicina minori).
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A - Uranus.jpgUranus from Voyager 2109 visiteUranus Data and Statistics
Discovered by William Herschel
Date of discovery = AD 1781
Mass (kg) = 8.686e+25
Mass (Earth = 1) = 1,4535e+01
Equatorial radius = 25.559 Km
Equatorial radius (Earth = 1) = 4,0074
Mean density (gm/cm^3) = 1,29
Mean distance from the Sun = 2.870.990.000 Km
Mean distance from the Sun (Earth = 1) = 19,1914
Rotational period (hours) = - 17,9
Orbital period (years) = 84,01
Mean orbital velocity = 6,81 Km per second
Tilt of axis = 97,86°
Orbital inclination = 0,774°
Equatorial surface gravity (m/sec^2) = 7,77
Equatorial escape velocity = 21,30 Km per second
Magnitude (Vo) = 5,52
Mean cloud temperature = - 193°C
Atmospheric pressure (bars) = 1,2
Atmospheric composition: Hydrogen 83%; Helium 15%; Methane 2%
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Miranda-PIA00042_modest.jpgMiranda in natural colors (elab. NASA)109 visiteCaption NASA originale:"This color composite of the Uranian satellite Miranda was taken by Voyager 2 on Jan. 24, 1986, from a distance of 147.000 Km (91.000 miles). This picture was constructed from images taken through the narrow-angle camera's green, violet and ultraviolet filters. It is the best color view of Miranda returned by Voyager. Miranda, just 480 Km (300 mi) across, is the smallest of Uranus' 5 major satellites. Miranda's regional geologic provinces show very well in this view of the Southern Hemisphere, imaged at a resolution of 2,7 km (1,7 mi). The dark and bright-banded region with its curvilinear traces covers about half of the image. HR pictures taken later show many fault valleys and ridges parallel to these bands. Near the terminator (at right), another system of ridges and valleys abuts the banded terrain; many impact craters pockmark the surface in this region. The largest of these are about 30 Km in diameter; many more lie in the range of 5 to 10 Km in diameter".
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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)107 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
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URANUS from HST.jpgUranus from the Hubble Space Telescope106 visiteUrano, il terz'ultimo Pianeta del Sistema Solare, fa parte della famiglia dei "Giganti Gassosi", assieme a Giove, Saturno e Nettuno. In ordine di grandezza Urano è il terzo Pianeta dopo Giove e Saturno e, dal punto di vista della sua struttura, esso assomiglia (quasi) come una goccia d'acqua a Nettuno.
Al pari di questo, infatti, la (spessissima) atmosfera di Urano appare costituita principalmente da Idrogeno ed Elio con una sensibile presenza, nei suoi strati più alti, di Metano (il quale conferisce al Pianeta il suo caratteristico colore azzurrino).
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Miranda-PIA01354_modest.jpgMiranda (close-up of the Verona Rupes Region) - HR106 visiteCaption NASA originale:"Miranda, innermost of Uranus' large satellites, is seen at close range in this Voyager 2 image, taken Jan. 24, 1986, as part of a HR mosaicing sequence. Voyager was some 36.000 Km (22.000 miles) away from Miranda. This clear-filter, narrow-angle image shows an area about 250 Km (150 mi) across, at a resolution of about 800 meters (2.600 feet). Two distinct terrain types are visible: a rugged, higher-elevation terrain (right) and a lower, striated terrain. Numerous craters on the rugged, higher terrain indicate that it is older than the lower terrain. Several scarps, probably faults, cut the different terrains.
The impact crater in the lower part of this image is about 25 Km (15 mi) across".
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Titania from Voyager 2.jpgTitania from Voyager 2 (2)105 visitenessun commento
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AAA-Uranus&Co..jpgThe Uranus' "Family"103 visitenessun commento
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