| Ultimi arrivi - Neptune and His Moons |
Triton3.jpgThin clouds on Triton127 visiteDeboli e sottilissime nuvole (strati) caratterizzano, saltuariamente, il cielo di Tritone. Un Mondo lontano e gelido che riceve, mediamente, poco più di 1/400mo della luce che la Terra riceve dal Sole, eppure...Eppure Tritone possiede un'atmosfera ed essa mostra (come risulta evidente da questa immagine) di essere "viva" e capace di esprimere "fenomeni" quali nuvole e venti. Probabilmente passerà un secolo (o anche di più) prima che qualche Governo finanzi una Missione ricognitiva del Sistema di Nettuno e - magari - simile, in termini di contenuti, alla Missione "Cassini-Saturno". Certamente, quando avremo avuto risposte significative alle domande che ci stiamo ponendo in questo momento, coloro che scrivono sulle pagine di Lunar Explorer non ci saranno più.
Ma è questo, forse, il fascino della Scienza: Essa non si ferma mai e, se c'è la Volontà, qualcuno riprende sempre il lavoro interrotto da altri e, prima o poi, lo conduce al termine...
Original caption:"This image of Triton shows a thin cloud layer along the limb of the moon. The image was obtained as Voyager 2 swept past Triton at a speed of 27 kilometers per second and passed within 39,800 kilometers. Voyager discovered that Triton possessed a thin atmosphere of 15 microbars or 0.000015 times the surface pressure on Earth at sea level. The limb of Triton also showed a thin haze about 13 kilometers from the surface of the planet and thin patches of clouds as shown by this image".Ott 28, 2005
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Nereid-CJH.gifNereid55 visiteNereid was discovered in 1949 by astronomer Gerard Kuiper. Nereid is about 340 Km (210 miles) in diameter and is so far from Neptune that it requires 360 days to make one orbit. Voyager's best photos of Nereid were taken from about 4,7 MKM (about 2,9 MMs). The photos show that the moon's surface reflects about 14% of the sunlight that strikes it, making it somewhat more reflective than Earth's Moon and more than twice as reflective as Proteus. Nereid's orbit is the most eccentric in the Solar System. Its distance to Neptune ranges from about 1.353.600 Km (about 841.100 miles) to 9.623.700 Km (such as about 5.980.200 miles). Ott 27, 2005
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Neptune_sEye-TheDarkSpot-V2-CJH.gifThe "Dark Spot" of Neptune64 visitenessun commentoOtt 27, 2005
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AAA-NeptuneandTriton-CJH.gifNeptune and Triton in natural colors - from Voyager 258 visiteNon si possono fare commenti ad immagini suggestive come questa: Vi lasciamo con la Vostra Fantasia ed Immaginazione, per provare a sentire che cosa questa "corsa infinita" del Voyager 2 Vi suggerisce...Ott 27, 2005
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AA-Neptune-CJH.jpgSmiling Neptune and soft, white, water-clouds - from Voyager 2 (HR)66 visiteUn'immagine davvero meravigliosa, ottenuta dalla Sonda Voyager 2, durante il suo rapido passaggio accanto all'ultimo Gigante Gassoso del nostro Sistema Solare. Era il 31 Agosto 1989...Ott 27, 2005
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Proteus2.jpgProteus (HR)55 visitenessun commentoOtt 25, 2005
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Neptune-PIA00048.jpgNeptune in true colors, from Voyager 270 visiteOriginal caption:"This image of clouds in Neptune's atmosphere is the first that tests the accuracy of the weather forecast that was made eight days earlier (nota: questa caption è relativa all'Estate del 1989) to select targets for the Voyager narrow angle camera. Three of the four targeted features are visible in this photograph; all 3 are close to their predicted locations.
The "Great Dark Spot" with its bright white companion is slightly to the left of center. The small bright "Scooter" is below and to the left, and the second "Dark Spot" with its bright core is below the Scooter. Strong eastward winds up to 400 mph cause the second dark spot to overtake and pass the larger one every five days. The spacecraft was 6,1 MKM (about 3,8 MMs) from the Planet at the time of camera shuttering, and the images uses the orange, green and clear filters of the camera".
Qualche nota sui Voyager 1 e 2: Voyager 1, launched September 5, 1977, visited Jupiter in 1979 and Saturn in 1980. It is now leaving the solar system, rising above the ecliptic plane at an angle of about 35 degrees, at a rate of about 520 million kilometers a year.
Voyager 2, launched August 20, 1977, visited Jupiter in 1979, Saturn in 1981 and Uranus in 1986 before making its closest approach to Neptune on August 25, 1989. Voyager 2 traveled 12 years at an average velocity of 19 kilometers a second (about 42,000 miles an hour) to reach Neptune, which is 30 times farther from the Sun than Earth is. Voyager observed Neptune almost continuously from June to October 1989. Now Voyager 2 is also headed out of the solar system, diving below the ecliptic plane at an angle of about 48 degrees and a rate of about 470 million kilometers a year.
Both spacecraft will continue to study ultraviolet sources among the stars, and their fields and particles detectors will continue to search for the boundary between the Sun's influence and interstellar space. If all goes well, we will be able to communicate with the two spacecraft for another 20 years, until their radioactive power sources can no longer supply enough electrical energy to power critical subsystems.
Ott 25, 2005
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Neptune-newmoons-PIA01991.jpgNew moons of Neptune64 visiteThis image captured by the Voyager 2 was used to confirm the discovery of 3 new moons orbiting Neptune. The 46" exposure was taken by Voyager 2's narrow angle camera through a clear filter on July 30, 1989, when the spacecraft was about 37,3 MKM (or 23,6 MMs) from Neptune. The large globe of the planet itself is severely overexposed and appears pure white. The image has been computer processed to accentuate the new moons, which otherwise would appear little stronger than background noise. The satellite 1989 N1, at right in this frame, was discovered by Voyager 2 in early July 1989. The new satellites are 1989 N2, 1989 N3 and 1989 N4. Each of the moons appears as a small streak: an effect caused by movement of the spacecraft during the long exposure. The new moons occupy nearly circular and equatorial orbits ranging from about 27.300 to 48.300 Km (such as 17.000 to 30.000 miles) from Neptune's cloud tops, and are estimated to range in diameter from about 100 to 200 Km (such as 60 to 125 miles).Mar 15, 2005
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Triton-clouds-PIA02203.jpgClouds on the limb of Triton75 visiteCaption NASA originale:"Limb clouds over Triton's South Polar Cap. Image is stretched to enhance the limb clouds and surface features. The image shows the cloud on the west limb that extends about 100 Km along the limb and appears detached over much of its length".
Nuvole nel cielo di Tritone: non si tratta di un'ipotesi affascinante, bensì di un fatto. Ora la domanda non può che essere questa: qual'è la composizione delle nuvole di Tritone?Mar 15, 2005
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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]"Mar 15, 2005
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Neptune-shadows-PIA02220.jpg"Cloud shadows" on Neptune56 visiteCaption NASA originale:"This image of Neptune shows the discovery of shadows in Neptune's atmosphere, shadows cast onto a deep cloud band by small elevated clouds. They are the first cloud shadows ever seen by Voyager 2 on any planet. Estimates of the height of these discrete clouds above the underlying cloud bank can be obtained by careful analysis of this data".Mar 15, 2005
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Neptune-bw-PIA02222.jpgNeptune and the "Great Dark Spot"84 visiteCaption NASA originale:"This photo was taken by Voyager 2's wide-angle camera. 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. Other, smaller clouds associated with the Great Dark Spot are white, and are also at high altitudes.
The Voyager Mission was conducted by JPL for NASA's Office of Space Science and Applications".Mar 15, 2005
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