| Ultimi arrivi - Neptune and His Moons |
Neptune-PIA01539_modest.jpgFarewell Neptune: a "bright smile" for the Earthlings...61 visiteCaption NASA originale:"Voyager 2's post-encounter view of Neptune's South Pole as the spacecraft sped away on a southward trajectory".
E con la Sonda Voyager 2 che sfiorava Nettuno e poi si dirigeva verso i più estremi confini del Sistema Solare - perdendosi per sempre nello spazio interstellare - quest'ultimo frame ci mostra (passateci il termine) il "sorriso" di Nettuno per noi Terrestri.
Un "luminoso sorriso" che a noi piace pensare sia il suo modo di dire "Arrivederci"...Ago 26, 2004
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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".Ago 26, 2004
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ZB-Neptune_s Partial Rings-PIA02200_modest.jpgNeptune's "Partial Rings" (or "Ring Arcs")57 visiteCaption NASA originale:"One of two new ring arcs, or partial rings, discovered by NASA's Voyager 2 spacecraft, is faintly visible here just outside the orbit of the Neptunian moon 1989N4, also discovered by Voyager 2.
The 155 second exposure taken by Voyager's narrow-angle camera shows the glare of an overexposed Neptune to the right of the moon and ring arc.
The two bright streaks below the moon and ring arc are stars.
The ring arc is approximately 50.000 Km (or 30.000 miles) long".Ago 26, 2004
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ZA-Neptune_s Rings-PIA01996_modest.jpgThe Rings of Neptune (closest approach)58 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". Ago 26, 2004
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ZA-Neptune_s Rings-PIA01997_modest.jpgThe Rings of Neptune (full system) 163 visiteCaption NASA originale:"These two 591-second exposures of the rings of Neptune were taken with the clear filter by the Voyager 2 wide-angle camera on Aug. 26, 1989 from a distance of 280.000 Km (175.000 miles). The 2 main rings are clearly visible and appear complete over the region imaged. The time between exposures was 1 hour and 27 minutes. [During this period the bright ring arcs in the outer bright ring were not visible in either picture (they were unfortunately on the opposite side of the planet for each exposure).] Also visible in this image is the inner faint ring at about 42.000 km (25.000 miles) from the center of Neptune and the faint band which extends smoothly from the 53.000 Km (33.000 miles) ring to roughly halfway between the 2 bright rings". Ago 26, 2004
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ZA-Neptune_s Rings-PIA02202_modest.jpgThe Rings of Neptune (full system) 255 visiteCaption NASA originale:"This pair of Voyager 2 images (FDS 11446.21 and 11448.10), two 591-s exposures obtained through the clear filter of the wide angle camera, show the full ring system with the highest sensitivity. Visible in this figure are the bright, narrow N53 and N63 rings, the diffuse N42 ring, and (faintly) the plateau outside of the N53 ring (with its slight brightening near 57.500 Km)". Ago 26, 2004
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Triton-PIA02214_modest.jpgTriton from Voyager 2 (false colors)67 visiteCaption NASA originale:"This false color image of Triton is a composite of images taken through the violet, green and ultraviolet filters. The image was taken early on Aug. 25, 1989 when Voyager 2 was about 190.000 Km (118.000 miles) from Triton's surface. The smallest visible features are about 4 Km(2,5 miles) across. The image shows a geologic boundary between completely dark materials and patchy light/dark materials. A layer of pinkish material stretches across the center of the image. The pinkish layer must be thin because underlying albedo patterns show through. Several features appear to be affected by the thin atmosphere; the elongated dark streaks may represent particulate materials blown in the same direction by prevailing winds and the white material may be frost deposits". Ago 26, 2004
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Triton-PIA02213_modest.jpgThe limb of Triton (natural colors - elab. NASA)55 visiteCaption NASA originale:"This natural color image of the limb of Triton was taken early in the morning of Aug. 25, 1989, when the Voyager 2 spacecraft was at a distance of about 210.000 Km (128.000 miles) from the icy satellite. The largest surface features visible area about 3 miles across. The picture is a composite of images taken through the violet, green and clear filters.
The image shows a geologic boundary between a rough, pitted surface to the right and a smoother surface to the left". Ago 26, 2004
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Neptune-PIA02245.jpgNeptune from 16.000.000 Km55 visiteCaption NASA originale:"This color image, produced from a distance of about 16 MKM, shows several complex and puzzling atmospheric features. The Great Dark Spot (GDS) seen at the center is about 13.000 Km by 6.600 km in size - as large along its longer dimension as the Earth. The bright, wispy "cirrus-type" clouds seen hovering in the vicinity of the GDS are higher in altitude than the dark material of unknown origin which defines its boundaries". Ago 26, 2004
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NEPTUNE from Palomar Obs.jpgNeptune and Triton from Earth (Palomar)90 visiteIn più di un'occasione, guardando le fotografie di Nettuno, l'impressione che possiamo ricavarne (così come accade per Venere) è alquanto rassicurante: un Pianeta prevalentemente azzurro (e verde!), striato da bianchissime formazioni nuvolose che tanto ricordano i nostri cirro/strati. La realtà, ancora una volta - e salvo prova contraria... -, è profondamente diversa. Nettuno è un Pianeta Gigante (uno dei 4 "Giganti Gassosi", per l'esattezza, assieme a Giove, Saturno ed Urano), posto ai confini del Sistema Solare ed immerso in una notte perenne.Lug 08, 2004
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PROTEUS.jpgProteus75 visiteUna luna minore del Sistema di Nettuno: Proteus.
Caratterizzata da una forma solo vagamente sferica, questa luna presenta un gigantesco - e facilmente visibile - cratere da impatto in prossimità del suo Polo Nord (fotografico).
Forse è proprio questo cratere la "cicatrice" generata dall'urto che ha spinto "Proteus" al di fuori dalla Fascia di Kuiper e poi verso Nettuno, dalla cui gravità è stato infine catturato.
Un probabilissimo KBO, dunque, o - come dicono alcuni - un Trans Neptunian Object.
O forse una cometa mancata.
Forse.Lug 08, 2004
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TRITON2.jpgTriton from Voyager 2 (enhanced real colors)78 visiteUn dettaglio della superficie di Tritone, sempre ripresa dal Voyager 2 (da notare che le gradazioni di colore e, conseguentemente, la qualità del dettaglio e dei particolari, sono state artificiosamente accentuate/i).
Una curiosità: a quanto è stato possibile accertare sino ad ora, le caratteristiche morfologiche superficiali di Tritone sembrano davvero molto simili a quelle di Plutone. Due mondi simili (due KBOs?) con un comune passato remoto e che, magari, sono destinati ad un comune lontano futuro...Lug 08, 2004
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