| Piú viste - Neptune and His Moons |
ZC-Neptune_s Rings-PIA01493_modest.jpgThe Rings of Neptune66 visiteCaption NASA originale:"In Neptune's outermost ring, 39.000 miles out, material mysteriously clumps into 3 arcs.
Voyager 2 acquired this image as it encountered Neptune in August 1989".
|
|
Triton-PIA00056_modest.jpgTriton's limb66 visiteCaption NASA originale:"Voyager 2 acquired this black and white image of Triton, Neptune's largest satellite, during the night of Aug. 24-25, 1989. Triton's limb cuts obliquely across the middle of the image. The field of view is about 1.000 Km (600 miles) across. Three irregular dark areas, surrounded by brighter material, dominate the image. Low-lying material with intermediate albedo occupies the central area, and fresh craters occur along the right margin. Sub-parallel alignment of linear patches of dark material shown in the lower and left part of the image suggests that the patches are structurally controlled".
|
|
Neptune-crescent-PIA02204_modest.jpgNeptune's bright crescent66 visiteCaption NASA originale:"Neptune's bright crescent taken in six filters (from bottom to top: UV, violet, blue, clear, green, orange) on August, 31, 1989. The images were shuttered in temporal order: violet, blue, UV, clear, green, orange. These images how the bright core of D2, the South Polar feature, and the symmetric structure immediately surrounding the South Pole. The relatively high contrast of the features in these images indicates that they extend above most of the scattering haze and absorbing methane gas in Neptune's atmosphere. [Image processing by D.A. Alexander]"
|
|
ZA-Neptune_s Rings-PIA01996_modest.jpgThe Rings of Neptune (closest approach)65 visiteCaption NASA originale:"The Voyager 2 spacecraft took this picture after closest approach to Neptune on Aug. 25 1989, using the clear filter of the wide-angle camera with an exposure time of 255 seconds. The view back towards Neptune at a phase angle of 135° found the 2 known rings to be 5 to 10 times brighter than seen in backscattering during Voyager approach at much lower phase angle. This brightness increase implies a large percentage of microscopic particles within the rings".
|
|
ZA-Triton-PIA02247_modest.jpgFarewell Triton...65 visiteCaption NASA originale:"Voyager 2 obtained this parting shot of Triton, Neptune's largest satellite, shortly after closest approach to the moon and passage through its shadow on the morning of Aug. 25, 1989. The distance to Triton was 90.000 Km and the phase angle was 155°, so that only a thin crescent of Triton's south polar region can be seen. Because of the high phase angle, and perhaps because of scattering sunlight in Triton's hazy atmosphere, few surface features are also easily discernible". Un piccolo commento: non sembra anche a Voi di intuire una sottile somiglianza fra Tritone e Titano?...
|
|
Neptune and Triton - PIA01491_modest.jpgNeptune and Triton65 visiteCaption NASA originale:"This image was returned by the Voyager 2 spacecraft on July 3, 1989, when it was 76 MKM from Neptune. The planet and its largest satellite, Triton, are captured in the field of view of Voyager's narrow-angle camera through violet, clear and orange filters. Triton appears in the lower right corner at about 5 o'clock relative to Neptune.
Recent measurements from Voyager images show Triton to be between 1.400 and 1.800 Km in radius with a surface that is about as bright as freshly fallen snow".
|
|
s Rings-PIA02207_modest.jpgNeptune's Rings (and a crescent Neptune) from 1,1 MKM65 visiteCaption NASA originale:"This wide-angle Voyager 2 image, taken through the camera's clear filter, is the first to show Neptune's rings in detail. The 2 main rings, about 53.000 Km and 63.000 Km from Neptune, are 5 to 10 times brighter than in earlier images and the difference is due to lighting and viewing geometry. In approach images, the rings were seen in light scattered backward toward the spacecraft at a 15° phase angle. However, this image was taken at a 135° phase angle as Voyager 2 left the planet. That geometry is ideal for detecting microscopic particles that forward-scatter light preferentially. The fact that Neptune's Rings are so much brighter at that angle means the particle-size distribution is quite different from most of Uranus' and Saturn's rings, which contain fewer dust-size grains. However, a few components of the Saturnian and Uranian ring systems exhibit forward-scattering behavior: the F-Ring and the Encke Gap ringlet at Saturn, and 1986U1R at Uranus".
|
|
Neq-Neptune-PIA00051.jpgNeptune in false colors65 visiteCaption NASA originale:"In this false color image of Neptune, objects that are deep in the atmosphere are blue, while those at higher altitudes are white. The image was taken by Voyager 2's wide-angle camera through an orange filter and two different methane filters. Light at methane wavelengths is mostly absorbed in the deeper atmosphere. The bright, white feature is a high altitude cloud just south of the Great Dark Spot. The hard, sharp inner boundary within the bright cloud is an artifact of computer processing on Earth. Other, smaller clouds associated with the Great Dark Spot are white or pink, and are also at high altitudes. Neptune's limb looks reddish because Voyager 2 is viewing it tangentially, and the sunlight is scattered back to space before it can be absorbed by the methane. A long, narrow band of high altitude clouds near the top of the image is located at 25° north latitude and faint hazes mark the equator and polar regions".
|
|
Triton-PIA12185.jpgVolcanic Plains on Triton65 visiteCaption NASA:"This view of the Volcanic Plains of Neptune's moon Triton was produced using topographic maps derived from images acquired by NASA's Voyager Spacecraft during its August 1989 flyby, 20 years ago this week (August 2009).
Triton, Neptune's largest natural moon, was the last solid object visited by the Voyager 2 Spacecraft on its epic 10-year tour of the Outer Solar System. This view shows a close-up of a prominent chain of Volcanic Features surrounded by smooth Volcanic Plains formed by lavas or ash deposits of water or other ices, such as Methane or Ammonia.
The smaller pits and domes are typically 10 Km (about 6 miles) across and have relief of no more than a few hundred meters (several hundred feet).
The large depressions at the far left and right of the chain are 50 to 80 Km (about 31 to 50 miles) across.
The Surface of Triton is very rugged, scarred by rising blobs of ice (diapirs), faults and volcanic pits and lava flows composed of water and other ices. The Surface is also extremely young and sparsely cratered and could be geologically active today.
This scene is on the order of 500 Km (about 310 miles) across and is taken from a new flyover movie across the Equatorial Regions of Triton commemorating the Voyager anniversary of the Triton flyby.
Vertical relief has been exaggerated by a factor of 25 to aid interpretation".MareKromium
|
|
Nereid-V2-PIA00054.jpgNereid64 visiteUn'immagine certo non magnifica, ma di grande valore e molto rara: si tratta di Nereide, la seconda delle due Lune Maggiori di Nettuno. I dettagli che possono percepirsi da questa fotografia ottenuta dal Voyager 2 sono troppo indefiniti per poter azzardare delle valutazioni, ma l'ipotesi pių probabile relativamente alle fattezze di Nereide, č che si tratti di un piccolo mondo fatto di roccia e ghiaccio, dalla forma irregolare, ricoperto di crateri da impatto e costellato da crepacci che ne rendono la superficie completamente inospitale.
Forse, come sostengono alcuni Scienziati, si potrebbe trattare di un KBO catturato da Nettuno in tempi assai remoti.
|
|
Triton-PIA01536_modest.jpgTriton (through green, violet and ultraviolet filters)64 visiteCaption NASA originale:"This color photo of Neptune's large satellite Triton was obtained on Aug. 24 1989 at a range of 530.000 Km (or 330.000 miles). The resolution is about 10 Km (6,2 miles), sufficient to begin to show topographic detail. The image was made from pictures taken through the green, violet and ultraviolet filters. In this technique, regions that are highly reflective in the ultraviolet appear blue in color. In reality, there is no part of Triton that would appear blue to the eye. The bright southern hemisphere of Triton, which fills most of this frame, is generally pink in tone as is the even brighter equatorial band. The darker regions north of the equator also tend to be pink or reddish in color".
|
|
Triton-PIA00317_modest.jpgTriton (False Colors; credits: NASA/JPL/USGS)64 visiteCaption NASA originale:"The color was synthesized by combining HR images taken through orange, violet and ultraviolet filters; these images were displayed as red, green and blue images and combined to create this color version. With a radius of 1.350 Km, about 22% smaller than Earth's Moon, Triton is by far the largest satellite of Neptune. It is 1 of only 3 objects in the Solar System known to have a nitrogen-dominated atmosphere (the others are Earth and Saturn's giant moon, Titan). Triton has the coldest surface known anywhere in the Solar System (38 K, about -391 degrees F); it is so cold that most of Triton's nitrogen is condensed as frost, making it the only satellite in the Solar System known to have a surface made mainly of nitrogen ice. The pinkish deposits constitute a vast south polar cap believed to contain methane ice, which would have reacted under sunlight to form pink or red compounds. The dark streaks overlying these pink ices are believed to be an icy and perhaps carbonaceous dust deposited from huge geyser-like plumes, some of which were found to be active during the Voyager 2 flyby. The bluish-green band visible in this image extends all the way around Triton near the equator; it may consist of relatively fresh nitrogen frost deposits. The greenish areas includes what is called the cantaloupe terrain, whose origin is unknown, and a set of "cryovolcanic" landscapes apparently produced by icy-cold liquids (now frozen) erupted from Triton's interior".
|
|
| 96 immagini su 8 pagina(e) |
 |
|
|
|
6 | |
|
