| Piú viste - Uranus and His Moons |
Uranus-2003.jpgGoing, Going, Gone: Hubble captures Uranus's Rings on Edge (1)55 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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Miranda-A86-7026_a.jpgMiranda (possible natural colors; credits: Lunexit)55 visitenessun commentoMareKromium
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UranusfromHST-3.JPGUranus, from HST (Natural, but enhanced, Colors; credits: NASA)55 visitenessun commentoMareKromium
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UranusfromHST-1.JPGUranus, from HST (False Colors; credits: NASA)55 visitenessun commentoMareKromium
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VC-Belinda-V2.jpgBelinda - Voyager 254 visiteEd ora una carrellata relativa ad alcune delle Lune "minori" di Urano. La maggior parte di esse è stata scoperta ex-post, cioè analizzando le immagini mandateci alcuni anni fa dai nostri Messaggeri inviati ai confini del Sistema Solare: le Sonde Voyager 1 e 2. Si tratta di mondi assai minuscoli, dalle forme irregolari, probabilmente non originari del Sistema di Urano, ma "catturati" dal Gigante Gassoso in epoche più o meno remote. Forse, queste Lune minori, sono delle "comete mancate" o forse sono frammenti, schegge di corpi celesti più grandi entrati in collisione quando il Sistema Solare era ancora - relativamente - "giovane". Qualunque sia la verità (che, probabilmente, non conosceremo mai), noi Vi offriamo le immagini che abbiamo raccolto in giro per la Rete e desideriamo ringraziare l'Ing. Calvin J. Hamilton, creatore e curatore del bellissimo Sito conosciuto come "Views of the Solar System".
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VAA-Uranus Rings.2jpg.jpgBeautiful Starfield, through Uranus' Rings54 visitenessun commento
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UranusinTime.jpgUranus along the years...54 visiteCaption NASA originale:"This diagram shows how the inclination of orbits of Uranus' moons have appeared increasingly more oblique over the past 12 years due to Uranus's orbit about the Sun. Hubble Space Telescope has been watching Uranus over that period and has traced, in detail, our changing view of the Planet. Uranus is tilted so that its spin axis lies nearly in its orbital plane. This means that only around the time when Uranus's equator is aimed at the Sun (every 42 years) do the orbits of its satellites lie edge-on to the Sun, allowing their shadows to strike the Planet, producing Solar Eclipses on the Planet".
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Uranus-Hurricane00.jpgUranian Hurricane (context image)54 visiteCaption NASA originale:"Just as we near the end of the hurricane season in the Atlantic Ocean, winds whirl and clouds churn 2 BMs away in the atmosphere of Uranus, forming a dark vortex large enough to engulf two-thirds of the United States.
Lawrence Sromovsky of the University of Wisconsin-Madison leads a team that used NASA's HST to take the first definitive images of a dark spot on Uranus. The elongated feature measures 1.100 by 1.900 miles (such as about 1.700 by 3.000 Km).
There have been prior unconfirmed sightings of dark spots on Uranus, including sketches made in the early 1900s, low-contrast ultraviolet Voyager spacecraft flyby images in 1986, and near-infrared observations taken from a ground-based Observatoryin 1993. However, no other HST images taken almost every Summer from 1994 up to 2006 have shown such a dark spot.
This indicates that the current dark disturbance probably formed very recently (...)".
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Uranus-Hurricane02.jpgUranian Hurricane (detail 2)54 visitenessun commento
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Uranus-HST-PIA01283.jpgUranus' Rotation from HST54 visiteThese 3 NASA HST images of the planet Uranus reveal the motion of a pair of bright clouds in the Planet's Southern Hemisphere, and a high altitude haze that forms a "cap" above the Planet's South Pole.
Hubble's view was obtained on August 14, 1994, when Uranus was 1,7 BM (about 2,8 BKM) from Earth. These atmospheric details were only previously seen by the Voyager 2 spacecraft, which flew by Uranus in 1986. Since then, detailed observations of Uranus's atmospheric features have not been possible because the Planet is at the resolution limit of ground-based telescopes.
Hubble's Wide Field Planetary Camera 2 observed Uranus through a filter that is sensitive to light reflected by a pair of high altitude clouds. This makes a high altitude haze over Uranus' south polar region clearly visible, along with a pair of high altitude clouds or plume-type features that are 2500 and 1800 miles (4300 and 3100 kilometers) across, respectively. This sequence of images shows how the clouds (labeled A and B) rotate with the planet during the three hours that elapsed between the first two observations (left and center picture) and the five hours that elapsed between the second pair of observations (center and right picture). Some cloud motion might be due to high altitude winds on the planet. (Observations are indicated in Universal Time.)
By tracking the motion of high-altitude clouds, the new Hubble observations will allow astronomers to make new measurements of Uranus' rotation period. Based on the previous Voyager observations, Uranus spins on its axis at a faster rate than Earth does, completing one rotation every 7 hours, 14 minutes.
One of the four gas giant planets of our solar system, Uranus is largely featureless. Unlike Earth, Uranus' south pole points toward the Sun during part of the planet's 84-year orbit. Thanks to its high resolution and ability to make observations over many years, Hubble can follow seasonal changes in Uranus's atmosphere, which should be unusual given the planet's large tilt.
The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.
MareKromium
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Uranus-2007-01.jpgGoing, Going, Gone: Hubble captures Uranus's Rings on Edge (4)54 visitenessun commentoMareKromium
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Uranus-2007-00.jpgGoing, Going, Gone: Hubble captures Uranus's Rings on Edge (3)54 visiteCaption NASA:"Showalter is a member of a team led by Imke de Pater of the University of California, Berkeley, who reported that the Rings of micron-sized dust have changed significantly since the Voyager 2 spacecraft photographed the Uranus System 21 years ago. Observations were also gleaned from near-infrared adaptive optics observations with the Keck II telescope on May 28, 2007, and reported in an article appearing on August 23 in Science Express, the online edition of Science Magazine".MareKromium
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