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| Piú votate - Neptune and His Moons |
Triton-vg2_p34665.jpgTriton (in natural colors and HR)53 visitenessun commento
(4 voti)
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Triton-PEI.jpgMoments of Triton...56 visiteThis set of images shows the best views of Neptune's moon Triton taken by Voyager 2 as the spacecraft withdrew from the Neptune system on August 25, 1989. The top four images were constructed from various color image bands as Voyager receded from Triton.
The third image from the left is sharper than the other four, because it was taken with the Narrow Angle Camera, with Triton filling two thirds of the frame. The thin crescent first image, while much closer, spanned about a quarter of the frame. The second image was somewhat smaller, and the last was very small. The first of the four images was composed of Blue, Green, and Orange filter images. The second utilized Violet, Green, and Orange Filtered images. In both composites, the Orange image was of poorer quality. In the fourth image, no orange was available, and the green and blue images were badly smeared, though somewhat salvageable. A clear filtered image (also smeared) was substituted for orange. They were combined and used as a color overlay for a slightly overexposed, but sharp clear filtered view. The third image is composed of a Violet and a Green wide-angle image. Like all the images in the first and second composites, and like the images used to color the fourth composite, these images were underexposed. However, they were very sharp. The orange image came from a poor quality wide angle orange image. The resulting color image was combined with a well exposed clear filter image to provide the detail
The Narrow Angle images used in these mosaics were the first obtained after closest approach, with the exception of a single clear filter image obtained while the disk was about twice as big as what could be framed in the camera's field of view. It is very noisy, and by far the worst underexposure of them all, and could not be processed to the point in which the whole image could be made presentable. However, a few sections were salvaged. The first (lower left) was binned to make up for noisiness and sharpened. It was then merged with the color data from the third image above. A cloud can be seen near the limb. To its right is an image of the cloud that has not been as heavily processed. The cloud itself is better presented, as it was far brighter than the surrounding area and hence more securely detected. Its shadow can be faintly made out to its right.
The next two images are the same, but one to the right was merged with color data. The image is towards the center of the crescent, the brightest area, in which white spots can be seen. Although a few of them may be impact craters, this area, as most of the crescent, is over the south polar cap, and thus frost covered, and the appearance of this area most closely resembles the cantaloupe terrain seen on the other hemisphere before closest approach. The final image (lower right) hints of surface topography near the terminator. It seems it is one of the more rugged parts of Triton. The large, foreshortened circular feature slightly below the center of the image is a dimple similar those found in the cantaloupe terrain. The other features are too ambiguous to determine whether or not they are of the same nature.
(4 voti)
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Neptune-crescent-PIA02204_modest.jpgNeptune's bright crescent55 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]"
(4 voti)
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Neptune-clouds-PIA00047_modest.jpgThe clouds of Neptune (b/w) - 159 visiteCaption NASA originale:"The bright cirrus-like clouds of Neptune change rapidly, often forming and dissipating over periods of several to tens of hours. In this sequence Voyager 2 observed cloud evolution in the region around the Great Dark Spot (GDS). The surprisingly rapid changes which occur separating each panel shows that in this region Neptune's weather is perhaps as dynamic and variable as that of the Earth. However, the scale is immense by our standards - the Earth and the GDS are of similar size... - and in Neptune's frigid atmosphere, where temperatures are as low as 55 degrees Kelvin (-360 F), the cirrus clouds are composed of frozen methane rather than Earth's crystals of water ice".
(4 voti)
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Neptune-PIA01286_modest.jpgA new "dark spot" on Neptune, as seen by HST54 visiteCaption NASA originale:"NASA's HST has discovered a new Great Dark Spot, located in the Northern Hemisphere of Neptune. Because the planet's Northern Hemisphere is tilted away from Earth, the new feature appears near the limb of the planet.
The Spot is a near mirror-image to a similar Southern Hemisphere Dark Spot that was discovered in 1989 by the Voyager 2. In 1994, HST showed that the Southern Dark Spot had gone. Like its predecessor, the new Spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The Dark Spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere. Planetary scientists do not know how long this new feature might live. HST's HR images will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere. This image was taken on 2.11-'94 with HST's Wide Field Planetary Camera 2, when Neptune was 4,5 BKMs from Earth".
(4 voti)
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Triton-PIA01536_modest.jpgTriton (through green, violet and ultraviolet filters)57 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".
(4 voti)
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Triton-PIA02212_modest.jpgTriton from Voyager 2 (false colors?)54 visiteCaption NASA originale:"The smallest features that can be seen in this false color image of Neptune's largest satellite, Triton, are about 47 Km across. The image, taken by Voyager 2 early in the morning of Aug. 23, 1989, is a composite of three images taken through ultraviolet, green, and violet filters. The image offers an example of the kinds of puzzles scientists face on the eve of an encounter: mottling in the bright southern hemisphere may be the result of topography, if Triton's crust is predominantly water ice, which is rigid at Triton's surface temperature. Alternatively, the mottling could be due to markings on a smooth surface, if the crust is composed of nitrogen, carbon monoxide, or methane ice, since they are soft at the same temperature". Nota: in questo frame la NASA parla chiaramente di "false colors" mentre nel successivo dice "natural colors". Ora a noi i "colors" di Tritone, nei due frames, sembrano identici.
Sono dunque entrambi "natural" o "false"? Dov'è la verità?
(4 voti)
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ZC-Neptune_s Rings-PIA01493_modest.jpgThe Rings of Neptune56 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".
(4 voti)
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Triton-PIA02246-PCF-LXTT-IPF.jpgStill in the Abyss (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunar Explorer Italia/Italian Planetary Foundation)77 visiteFeatures as small as approx. 100 Km (such as a little more than 62 miles) across can be seen in this Absolut Color Image of Neptune's moon Triton, photographed by the NASA - Voyager 2 Spacecraft on August 20, 1989, while it was still approx. 5,4 Million KiloMeters (such as about 3,35 Million Miles) from Neptune. Triton's overall light pinkish color may be due to the heavy irradiation (---> the action of the Cosmic Rays and other Charged Particles, including the ones forming the Solar Wind) of the Ice (and, maybe, other Elements which were already) existing on the Surface of this distant Celestial Body.
The dark areas near the top of the image seem to be part of a belt of dark markings observed near Triton's Equator at different Longitudes. However - and generally speaking -, the darker areas visible on Triton appear to be somewhat redder in color than the brighter ones. The central Longitude in the image is 123° East. The South Pole of Triton is at about 6 o'clock of the disk, approximately 1/6th (one sixth) of the way up from its lower limb.
This frame (which is the Original NASA - Voyager 2 color frame published on the NASA - Planetary Photojournal with the ID n. PIA 02246) has been additionally processed and then re-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
(3 voti)
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Neptune-June2011-HST.jpgOne Neptunian Day...90 visiteCaption NASA:"Neptune rotates once on its axis in about 16 hours. So, spaced about 4 hours apart these 4 images of the Solar System's most distant Gas Giant cover one Neptune day. Recorded by the Hubble Space Telescope in late June 2011, they combine exposures made with visible and Near-InfraRed filters to show high-altitude Clouds composed of Methane ice crystals against the Planet's normally blue Cloud Tops.
Because Neptune's axis of rotation is tilted to its orbital plane by 29°, compared to Earth's 23,5°, Neptune experiences seasons analogous to Earth's.
As early Summer comes to Neptune's Southern Hemisphere and Winter to the North, Hubble observations have shown Cloud activity shifting to the Northern Hemisphere. In fact the progression of Neptune's seasons has come around once since its position was predicted by French mathematician Urbain Le Verrier and British mathematician John Couch Adams, and the Planet was subsequently discovered by German astronomer Johann Galle on September 23, 1846. With an orbital period of approximately 165 years, this week on July 12, 2011, Neptune has been once around the Sun since its discovery date".MareKromium
(3 voti)
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Triton-PIA12185.jpgVolcanic Plains on Triton58 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
(3 voti)
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Neptune-StrechedNaturalColors.JPGNeptune and a few of His Moons (Voyager 2 - Natural, but enhanced, Colors; credits: NASA)69 visiteCaption NASA:"Voyager 2 was the first spacecraft to observe the planet Neptune and its two satellites: Triton, the largest, and Nereid.
The most obvious feature of the Planet is its blue color, the result of Methane in the Atmosphere. Research continues on Neptune's two largest satellites and the additional 6 that were discovered by Voyager 2's investigation". MareKromium
(3 voti)
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