| Piú viste - Uranus and His Moons |
Uranus-2003.jpgGoing, Going, Gone: Hubble captures Uranus's Rings on Edge (1)93 visiteCaption NASA:"This series of images from NASA's HST shows how the Ring System around the distant planet Uranus appears at ever more oblique (shallower) tilts as viewed from Earth - culminating in the Rings being seen edge-on in 3 observing opportunities in 2007. The best of these events appears in the frame n. 3, taken with Hubble's Wide Field Planetary Camera 2 on August 14, 2007.
The "Edge-On Rings" appear as two spikes above and below the Planet. The Rings cannot be seen running fully across the face of the Planet because the bright glare of the planet has been blocked out in the Hubble photo (a small amount of residual glare appears as a fan-shaped image artifact). A much shorter color exposure of the Planet has been photo-composited to show its size and position relative to the Ring-Plane.
Earthbound astronomers only see Uranus Rings' edge every 42 years as the Planet follows a leisurely 84-year orbit about the Sun. However (and hironically), the last time the Rings were tilted Edge-On to Earth, astronomers didn't even know they existed".MareKromium
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VH-Juliet-V2.jpgJuliet - Voyager 292 visitenessun commento
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AAA-vg2_2684726.gifFlying over Uranus...92 visiteOriginal caption:"Image of Uranus taken by Voyager 2 about 21 minutes before closest approach. This image, centered at 4° South, 58° West, was taken with the wide angle camera. The frame is approx. 5.300 km from top to bottom and north is at 1:00. (Voyager 2, 26847.26)".
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UMBRIEL-vg2_p29502-B.jpgUmbriel's extremely unusual surface feature: Wunda Crater (HR - detail mgnf)92 visitenessun commento
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UranusfromHST-2.JPGUranus, from HST (Natural, but enhanced, Colors; credits: NASA)92 visitenessun commentoMareKromium
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ZB-Uranus-HP-V2-PIA01391_modest.jpgFarewell Uranus...91 visiteUna veduta finale di Urano, registrata dalla Sonda Voyager 2 il 27 Gennaio 1986. Come potete vedere chiaramente, Urano si sta facendo sempre più piccolo, quasi che fosse "divorato" dall'oscurità che lo circonda...
Quest'immagine, per Voyager 2 (e per noi tutti), rappresenta l'addio ad Urano ed al suo Sistema di Anelli e di Lune.
Ci torneremo mai? Sicuramente si, ma potrebbero passare tantissimi anni prima che ciò accada davvero...
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AB-Ariel-V2-PIA01534_modest.jpgBright Ariel!91 visiteSe osservata da una certa distanza (come in questa fotografia, ripresa da circa 150.000 Km), Ariel si dimostra essere una Luna decisamente luminosa, in particolar modo in alcune sue aree: a ridosso del Polo Sud ed in prossimità di alcuni dei suoi "Mari". L'elevatissima albedo di queste aree (ben visibili in questo frame) ci fa supporre che si possa trattare di una conseguenza della presenza di ghiaccio il quale, come sapete, assieme alle nuvole (laddove esistono), è causa dell'elevatissima albedo di alcuni corpi celesti (p.e.: Venere, Giove, Saturno ed alcune delle loro Lune maggiori).
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Uranus_and_Ariel.jpgUranus and Ariel: the Eclypse91 visiteCaption NASA originale:"This image is a never-before-seen astronomical alignment of a moon traversing the face of Uranus, and its accompanying shadow. The white dot near the center of Uranus' blue-green disk is the icy moon Ariel. The 700-mile-diameter satellite is casting a shadow onto the cloud tops of Uranus. To an observer on Uranus, this would appear as a solar eclipse, where the moon briefly blocks out the Sun as its shadow races across Uranus's cloud tops.
Though such "transits" by moons across the disks of their parents are commonplace for some other Gas Giant Planets, such as Jupiter, the satellites of Uranus orbit the planet in such a way that they rarely cast shadows on the Planet's Surface. Uranus is tilted so that its spin axis lies nearly in its orbital plane".
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Uranus-Hurricane01.jpgUranian Hurricane (detail 1)91 visitenessun commento
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Uranus-2005.jpgGoing, Going, Gone: Hubble captures Uranus' Rings on Edge (2)91 visiteCaption NASA:"With further analysis of the Hubble data, Astronomer Mark Showalter of the SETI Institute in Mountain View, Calif., hopes to detect some of the small moons that may shepherd the debris into distinct rings.
Until Voyager 2 flew by Uranus in January 1986, the Rings were only known from the way they temporarily blocked the light of stars passing behind the Planet. Hubble provided some of the first images of the Ring System as viewed from Earth's distance of approx. 2 BMs.
The advent of adaptive optics gave ground-based observers using large telescopes comparatively sharp views.
The Rings were discovered in 1977, so this is the first time for a Uranus Ring crossing to be observed from Earth. Earth's orbit around the Sun permits 3 opportunities to view the Rings in an "edge-on" configuration: Uranus made its first ring crossing as seen from Earth on May 3; it made its second crossing on August 16 and will cross for the third time on February 20, 2008.
Though the last ring crossing relative to Earth will be hidden behind the Sun, most of Earth's premier telescopes, including Keck, Hubble, the European Southern Observatory's Very Large Telescope and the Hale Telescope on Mt. Palomar, plan to focus on the planet again in the days following December 7, 2007. On December 7 the rings will be perfectly edge-on to the Sun".MareKromium
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VA-UranusRings-1.jpgUranus' Rings: yesterday, today, tomorrow91 visiteThe position of the Rings of Uranus from AD 1965 up to 2028.MareKromium
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VL-Rosalind-V2.jpgRosalind - Voyager 290 visitenessun commento
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