| Piú viste - Saturn: the "Ringed Beauty" and His Moons |
Helene-PIA08335-00.jpgHelene (HR and False Colors)55 visiteCaption NASA:"Cassini came close to Saturn's small moon Helene on Feb. 25, 2006, acquiring this High-Resolution (HR) view. This object seems to be buried in its own crater debris, like another Saturnian moon, Telesto.
Helene (32 Km, or 20 miles across) orbits 60° ahead of Dione in the larger moon's orbit, making it a "trojan" moon of Dione. Trojan moons are named for the Trojan group of asteroids that orbit 60° ahead of and behind Jupiter as it circles the Sun.
This image was taken in visible light with the Cassini spacecraft narrow-angle camera at a distance of approx. 68.000 Km (42.000 miles) from Helene and at a Sun-Helene-spacecraft, or phase, angle of 99°. Image scale is roughly 406 mt (1.334 feet) per pixel".
|
|
Saturn-PIA08340.jpgShadowlands55 visiteL'espressione "Shadowland/s" l'avevamo inventata un paio d'anni fa, per commentare le immagini che mostravano il profilo di rilievi elevati i quali si trovavano, al momento di effettuazione della ripresa, sul cosiddetto "Terminatore" (ossìa la linea che divide il giorno dalla notte).
E' non solo curioso ma anche, ed almeno dal nostro punto di vista, fonte di piacere il fatto di vedere che la NASA - chissà, forse anche ispirata da qualcuno dei "titoli" che diamo alle immagini... - abbia adottato questa medesima espressione per descrivere il regno di ombre che sembra caratterizzare, nel frame in oggetto, il Gigante Anellato più famoso del Sistema Solare: Saturno.
|
|
Rhea-N00075318.jpgRhea (natural colors)55 visitenessun commentoMareKromium
|
|
Mimas-N00077785.jpgOccultation? (4)55 visiteCaption NASA:"(...) The camera was pointing toward Mimas that, at the time, was at approximately 1.344.896 Km away, and the image was taken using the CL1 and CL2 filters (...)".
|
|
Mimas-N00077783.jpgOccultation? (2)55 visiteCaption NASA:"(...) The camera was pointing toward Mimas that, at the time, was at approximately 1.345.325 Km away, and the image was taken using the CL1 and CL2 filters (...)".
|
|
Mimas-N00077782.jpgOccultation? (1)55 visiteLa cosa più semplice da dire in sede di interpretazione di questo frame è che si dovrebbe trattare di una - davvero splendida - "occultazione", ossìa del transito di un Corpo Celeste sulla medesima linea visuale in cui si trova Mimas (dal punto di vista della Sonda Cassini) ed il susseguente verificarsi di una mini-eclisse.
Ma che cos'è il Corpo Celeste che viene "occultato" da Mimas? E' una stella? Secondo noi no, poichè le stelle, anche adoperando elevatissimi detail mgnf, non vengono risolte in maniera tale da mostrare dei dettagli superficiali.
Questo oggetto, invece, anche senza usare uno stretch eccessivo, si risolve in un disco e "sembra" evidenziare lievi/tenui dettagli superficiali.
Si tratta dunque di un Corpo Celeste molto più vicino all'Osservatore di quanto non lo sarebbe una stella. Che cosa sarà?
Con ogni probabilità, si tratta di un altra Luna Saturniana che, come già è accaduto tante volte in passato, viene colta in transito ravvicinato (un transito ravvicinato, come ovvio, solo apparente e determinato dal particolare movimento e relativo angolo visuale di Cassini) presso un'altra Luna del Gigante Anellato (pensate al bellissimo passaggio ravvicinato - con relativa occultazione - fra Rhea e Dione).
Oppure, se volete, si può anche pensare a qualcosa di più "esotico"...Vedete Voi!
Caption NASA:"(...) The camera was pointing toward Mimas that, at the time, was at approximately 1.345.535 Km away. and the image was taken using the CL1 and CL2 filters (...)".
|
|
Mimas-N00077789.jpgOccultation? (8)55 visiteCaption NASA:"(...) The camera was pointing toward Mimas that, at the time, was at approximately 1.344.003 Km away, and the image was taken using the CL1 and CL2 filters (...)".
|
|
Mimas-N00077788.jpgOccultation? (7)55 visiteCaption NASA:"(...) The camera was pointing toward Mimas that, at the time, was at approximately 1.344.230 Km away, and the image was taken using the CL1 and CL2 filters (...)".
|
|
Rhea-PIA08886.jpgDrawing Out Details on Rhea55 visiteRhea displays a marked color contrast from North to South that is particularly easy to see in the extreme color-enhanced Cassini spacecraft view presented here.
A clear filter image is also presented (left) alongside the color composite (right).
To create the false-color view, ultraviolet, green and infrared images were combined into a single picture that isolates and maps regional color differences.
This "color map" was then superimposed over a clear-filter image that preserves the relative brightness across the body.
The combination of color map and brightness image shows how colors vary across the surface of Rhea. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy surface material.
This view looks toward the Trailing Hemisphere on Rhea. The view shows southerly latitudes on Rhea, down to the South Pole. North is up and rotated 17° to the right.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 17, 2007 at a distance of approx. 457.000 Km (about 284.000 miles) from Rhea.
Image scale is roughly 3 Km (a little less than 2 miles) per pixel.
|
|
The_Rings-PIA08887.jpgHeading to the Darkness55 visiteCaption NASA:"This strikingly crisp view shows Atlas heading into Saturn's shadow at upper left. The moon's basic, elongated shape is easy to detect here. Above Atlas, a bright clump in the F-Ring also heads toward the darkness. This view looks toward the unlit side of the Rings from about 30° above the Ring-Plane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 19, 2007 at a distance of approx. 1,2 MKM (about 700.000 miles) from Atlas. Image scale is roughly 7 Km (about 4 miles) per pixel".
|
|
Helene_Mimas-PIA08897.jpgCelestial Wonders around Saturn: Helene and Mimas55 visiteCaption NASA:"Mimas (397 Km, or 247 miles across) is seen here just before gliding in front of Helene (32 Km, or 20 miles across), which lays about 192.000 Km (approx. 119.000 miles) in the distance beyond the larger moon.
The limb of Mimas is flattened in the West, where the rim if the large crater Herschel lies.
This view looks toward the lit side of the Rings from about 3° below the Ring-Plane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 3, 2007 at a distance of approx. 1,3 MKM (about 800.000 miles) from Mimas and 1,5 MKM (approx. 1 MMs) from Helene.
Image scale is roughly 8 Km (approx. 5 miles) per pixel on Mimas and 9 Km (about 6 miles) per pixel on Helene".
|
|
The_Rings-PIA08900.jpgThe "beginnings" of the Rings55 visiteCaption NASA:"High above the streamers of cloud in Saturn's atmosphere the Planet's immense Ring System begins with faint, thin rings populated with dust-sized ice particles. Here, features in the D-Ring are visible, beginning at about 67.000 Km (approx. 42.000 miles) from the Planet's center.
Stars trail across the background during this exposure, timed to capture the faint light from these D-Ring features.
This view looks toward the unlit side of the Rings, from about 59° above the Ring-Plane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 9, 2007 at a distance of approx. 1,7 MKM (1,1 MMs) from Saturn.
Image scale is roughly 10 Km (about 6 miles) per pixel".
|
|
| 2245 immagini su 188 pagina(e) |
 |
|
|
|
|
129 | |
|
|
|
|
