| Piú viste - Uranus and His Moons |
Uranus-2005.jpgGoing, Going, Gone: Hubble captures Uranus' Rings on Edge (2)54 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, tomorrow54 visiteThe position of the Rings of Uranus from AD 1965 up to 2028.MareKromium
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Miranda-B.JPGThe "Chevron Grooves" of Miranda (perspective view)54 visitenessun commentoMareKromium
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Uranus-Neptune-HST3_.JPGUranus and Neptune, from HST (Natural Colors and Enhanced Natural Colors; credits: NASA)54 visitenessun commentoMareKromium
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UMBRIEL-vg2_p29502-Wunda.jpgUmbriel's extremely unusual surface feature: Wunda Crater (Natural Colors; credits: NASA)54 visiteHere is a closeup systhesis from all the close-ups of Wunda Crater.
It is hard to tell if the craters dug up the bright material, or if they had something to do with the impacts. Maybe it was derived from eruptions or melting caused by impacts.
Or maybe they are some sort of frost left over from impacts.
This issue may not be resolved until another spacecraft observes Umbriel. Here is the best view of Wunda that can be generated with the available data.MareKromium
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UMBRIEL-vg2-SV.jpgUmbriel's most prominent Surface Features: Skynd and Wunda Craters (Natural Colors; credits: NASA)54 visiteThe surface of Umbriel is an ancient one.
A collection of impact craters of various sizes was found to saturate the landscape. As Voyager 2 drew closer, became clear that most or all of the bright features are related to craters. On the Terminator, one can see 2 interesting craters.
One, Skynd, has a bright Central Peak. The other, Wunda, at the top of the image, has a bright rim and no apparent Central Peak. This is the best color image obtained by Voyager 2.MareKromium
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UMBRIEL.jpgFarewell Umbriel! (Natural Colors; credits: Ted Stryk)54 visitenessun commentoMareKromium
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VB-Uranus-EpsilonRing-V2-PIA01983_modest.jpgUranus' Rings (4) - the "Epsilon Ring"53 visitenessun commento
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VM-Sycorax.jpgSycorax53 visitenessun commento
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VAA-Uranus Rings-1.jpgUranus' Rings (3)53 visiteCiò che intendiamo dire (l'ipotesi di lavoro che Vi proponiamo) è questo: forse gli Anelli di Giove, Urano e di Nettuno hanno un'origine diversa (almeno in parte) rispetto a quelli di Saturno. Gli Scienziati che vanno per la maggiore, infatti, pensano che la differenza nella "tessitura" degli Anelli tipici dei Giganti Gassosi dipenda solo dalle dimensioni originali del corpo celeste (o dei corpi celesti) dal cui disintegrarsi essi vennero generati: più grande era questo/i corpo/i, maggiore era il quantitativo di materiale che si distribuiva lungo l'orbita, più grande e maestosa (scenicamente) risultava la trama finale degli Anelli. Noi opiniamo che, forse, questa costruzione spiega gli Anelli di Giove, Urano e Nettuno ma non è sufficiente - da sola! - per spiegare l'origine degli Anelli di Saturno i quali ci appaiono troppo grandi e troppo complessi per essere derivati soltanto da un evento come quello dianzi ipotizzato.
Ne riparleremo ancora.
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Oberon-vg2_2683623.jpgLeaving Oberon (HR)53 visitenessun commento
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Oberon-vg2_2683625.jpgLeaving Oberon (HR)53 visitenessun commento
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