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Eros-NP-PIA02498.jpgThe North Pole of Eros52 visiteCaption NASA originale:"For a long time, imaging activities on the NEAR Shoemaker spacecraft have focused on the high northern latitudes of Eros. The point at which the Sun is directly overhead - known as the "subsolar point" - has been steadily moving from Eros' Northern Regions toward the equator as the asteroid's seasons progress. As this happens, the Northern Hemisphere is illuminated less and less and previously dark southern latitudes progressively come into view. In this image, taken March 19, 2000, from a range of 205 Km (approx. 127 miles), the asteroid's North Pole is in the upper right of the frame. The whole scene is 7,4 Km (approx. 4,6 miles) across".
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Eros from 700 mt - PIA03146_modest.jpgFalling down: Eros from 700 mt52 visiteCaption NASA:"...The image is 33 meters across. The large, oblong rock casting a big shadow measures 7.4 meters across...".
Riuscite a distinguere in questo scorcio ulteriormente ravvicinato qualche dettaglio il quale - ora, ovviamente, ingrandito - fosse gi presente nel frame precedente? Noi non ci siamo riusciti.
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Eros from 250 mt - PIA03147_modest.jpgFalling down: Eros from 250 mt60 visiteCaption NASA:"...The image is 12 meters across. The cluster of rocks at the upper right measures 1.4 meters across...". Vale quanto gi detto in precedenza: riuscite a vedere dei dettagli gi presenti nel frame precedente?!?
NEAR, scendendo, fotografa "random"?
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Eros from 120 mt - PIA03148_modest.jpgFalling down: Eros from 120 mt52 visiteCaption originale:"This is the last image of asteroid 433 Eros received from NEAR Shoemaker. Taken from a range of 120 meters, it measures 6 meters across. What we can see of the rock at the top of image measures 4 meters across. The streaky lines at the bottom indicate loss of signal as the spacecraft touched down on the asteroid during transmission of this image". La Sonda - probabilmente - si ribalta al momento del touch-down, il segnale si perde e la Missione termina per sempre. Sin qui l'ufficialit. Ufficiosamente, possiamo dirVi che la Sonda ha continuato a trasmettere dati ancora per molto tempo dopo l'impatto, ma su come abbia potuto farlo e di quali dati si trattasse, come potrete agevolmente intuire, non siamo riusciti a sapere assolutamente nulla. E' strano, per: la NASA avrebbe dovuto celebrare trionfalmente la sopravvivenza della Sonda NEAR all'impatto con l'asteroide, cos come sta trionfalmente celebrando la sopravvivenza "oltre le pi rosee aspettative" dei Mars Rovers, e invece...Silenzio.
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Eros from 1150 mt - PIA03145_modest.jpgFalling down: Eros from 1150 mt54 visiteIn sequenza, le ultime (?) 4 immagini ricevute sulla Terra e relative alla discesa della Sonda NEAR sull'asteroide Eros. Purtroppo non siamo in grado di operare delle valutazioni precise sul contenuto di questi frames i quali, per svariati ordini di motivi, NON ci convincono. I particolari della superficie di Eros variano da frame a frame (come se la Sonda stesse precipitando, seguendo una traiettoria non lineare), ma la qualit (in termini di definizione e nitidezza dei dettagli ripresi) dei singoli frames, invece, lascia supporre un landing morbido ed una discesa "smooth".
La NASA, inoltre, dice che "...The image is 54 meters across. The large rock at lower left is 7.4 meters across..." ma questi dati non sembrano totalmente convincenti.
Vediamo gli altri 3 frames...
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Eros - impact site - PIA03144_modest.jpgEros: NEAR-Shoemaker's Probe landing site52 visiteThis map projection of NEAR Shoemaker images shows locations and sizes of landmarks surrounding the spacecraft's planned landing site. Diameters of craters are shown in red, and diameters of boulders are shown in yellow. Diameters are given in units of meters (1 meter is about 3.3 feet). Coordinates along the left side of the map are degrees south latitude and coordinates along the bottom are degrees west longitude.
The six yellow "footprint" boxes represent approximate image size at 500, 1.000, 1.500, 2.000, 2.500 and 3.000 meters above the surface during descent. The spacecraft will take pictures continuously between each spot. The arrow marks the estimated touchdown site.
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Eris_Dysnomia.jpgEris and Dysnomia54 visiteNASA's HST has teamed up with the W.M. Keck Observatory to precisely measure the mass of Eris, the largest member of a new class of Dwarf Planets in our Solar System. Eris is 1,27 times the mass of Pluto, formerly the largest member of the Kuiper Belt of icy objects beyond Neptune.
Hubble observations in 2006 showed that Eris is slightly physically larger than Pluto. But the mass could only be calculated by observing the orbital motion of the moon Dysnomia around Eris. Multiple images of Dysnomia's movement along its orbit were taken by Hubble and Keck.
Astronomer Mike Brown of the California Institute of Technology in Pasadena, Calif. and colleagues also report in this week's Science Magazine that Dysnomia is in a nearly circular 16-day orbit. This favors the idea that Dysnomia was born out of a collision between Eris and another Kuiper Belt object (KBO).
A gravitationally captured object would be expected to be in a more elliptical orbit.
The satellites of Pluto, as well as the Earth-Moon system are also believed to have been born out of a collision process where debris from the smashup goes into orbit and coalesces into a satellite.
By comparing the mass and diameter, Brown has calculated a density for Eris of 2.3 grams per cubic centimeter. This is very similar to the density of Pluto, the large Kuiper Belt object 2003 EL61, and Neptune's moon Triton which is likely a captured KBO. These higher densities imply that these bodies are not pure ice but must have a significant rocky composition.
The discovery of Eris in 2005 (originally nicknamed Xena, and officially cataloged 2003 UB313) prompted a debate over the planetary status of Pluto because astronomers realized they would have to call it the "10th" planet if Pluto retained its own planetary status, which was already under debate. This led the International Astronomical Union, in 2006, to make a new class of solar system object called dwarf planets. These are spherical bodies in hydrostatic equilibrium (objects that have sufficient gravity to overcome their own rigidity and form a spherical shape) like the planets, but unlike the major planets in the solar system, they have not gravitationally cleared out the neighborhood of particles and small debris along their orbits.
MareKromium
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Eris.jpgAnother "Dwarf Planet" with satellite: 136199-Eris and Dysnomia53 visiteDa "NASA - Picture of the Day" del 18 Settembre 2006:"Is Pluto the largest Dwarf Planet? No! Currently, the largest known dwarf planet is 136199-Eris, renamed last week from 2003 UB313. Eris is just slightly larger than Pluto, but orbits as far as twice Pluto's distance from the Sun. Eris is shown above in an image taken by a 10-meter Keck Telescope from Hawaii, USA.
Like Pluto, Eris has a moon, which has been officially named by the International Astronomical Union as (136199) Eris I (Dysnomia). Dysnomia is visible above just to the right of Eris. Dwarf Planets Pluto and Eris are Trans-Neptunian Objects that orbit in the Kuiper belt of objects past Neptune. Eris was discovered in 2003, and is likely composed of frozen water-ice and methane. Since Pluto's recent demotion by the IAU from planet to dwarf planet status, Pluto has recently also been given a new numeric designation: 134340-Pluto.
Currently, the only other officially designated Dwarf Planet is 1-Ceres".
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EnckeCometTailRipoff_movie_short.gifComet Encke encounters a CME52 visiteCaption NASA:"Swinging inside the orbit of Mercury, on April 20th, 2007, periodic comet Encke encountered a blast from the Sun in the form of a Coronal Mass Ejection (CME). When CMEs, enormous clouds of energetic particles ejected from the Sun, slam into Earth's magnetosphere, they often trigger auroral displays.
But in this case, the collison carried the tail of the comet away.
The tail was likely ripped off by interacting magnetic fields rather than the mechanical pressure of the collision.
This a GIF-movie showing the remarkable event as recorded by the Heliospheric Imager onboard the STEREO A spacecraft. In the movie, the time between frames is about 45 minutes, while the frames span about 14x20 MKM at the distance of the comet. Of course, similar collisions have happened before as the ancient comet loops through its 3,3 year solar orbit. So don't worry, Encke's tail will grow back!".MareKromium
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EROS-PIA03143.jpgEros: NEAR-Shoemaker's Probe landing site74 visiteThe location of NEAR Shoemaker's landing site is shown in this image mosaic taken on December 3, 2000, from an orbital altitude of about 200 Km (approx. 124 miles). In this view, south is to the top and the terminator (the imaginary line dividing day from night) lies near the equator. The landing site (at the tip of the arrow) is near the boundary of two distinctly different provinces, both of which the spacecraft will photograph as it descends. To the south and east (above and to the left) lies older, cratered terrain, while to the north (down) is the saddle-shaped feature Himeros, whose lesser density of superposed craters indicates relatively recent resurfacing by geologic processes.
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EROS-PIA03129.jpgEros from above (2)62 visiteNEAR Shoemaker photographed this area of Eros on December 18, 2000, from an orbital altitude of 33 Km. This part of the asteroid's surface, like many others, appears vaguely "sculptured" due to its low, elongated ridges and depressions with seemingly consistent orientations. Some of the low spots also contain accumulations of smooth, pond-like materials. Neither the surface sculpturing nor the pond-like materials are well understood, and both will be investigated in detail using even higher-resolution images from NEAR Shoemaker's low passes over Eros in early 2001. The whole scene is about 1 Km across.
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EROS-PIA02951.jpgEros from above (1)57 visiteIn NEAR Shoemaker's long-awaited close-up images of Eros, the asteroid's small-scale features are revealing their fascinating diversity. This picture, taken July 8, 2000, from an orbital altitude of only 36 Km, shows a variety of differently shaped boulders. Some are nearly round, whereas others are elongated or even blade-shaped. Such varied shapes might arise from differences in the strength and fracturing of preexisting rock. The whole scene is about 1.4 Km across.
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