Fitxer:Saturn, its rings, and a few of its moons.jpg

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Fitxer original(7.227 × 3.847 píxels, mida del fitxer: 3,58 Mo, tipus MIME: image/jpeg)

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English: Seen from our planet, the view of Saturn's rings during equinox is extremely foreshortened and limited. But in orbit around Saturn, Cassini has no such problems. From 20 degrees above the ring-plane, Cassini's wide angle camera shot 75 exposures in succession for this mosaic showing Saturn, its rings, and a few of its moons a day and a half after exact Saturn equinox, when the Sun's disk was exactly overhead at the planet's equator. The novel illumination geometry that accompanies equinox lowers the Sun's angle to the ring-plane, significantly darkens the rings, and causes out-of-plane structures to look anomalously bright and to cast shadows across the rings. These scenes are possible only during the few months before and after Saturn's equinox which occurs only once in about 15 Earth years. Also at equinox, the shadows of the planet's expansive rings are compressed into a single, narrow band cast onto the planet as seen in this mosaic.

The images comprising the mosaic, taken over about eight hours, were extensively processed before being joined together. First, each was re-projected into the same viewing geometry and then digitally processed to make the image "joints" seamless and to remove lens flares, radially extended bright artefacts resulting from light being scattered within the camera optics. At this time so close to equinox, illumination of the rings by sunlight reflected off the planet vastly dominates any meagre sunlight falling on the rings. Hence, the half of the rings on the left illuminated by planet-shine is, before processing, much brighter than the half of the rings on the right. On the right, it is only the vertically extended parts of the rings that catch any substantial sunlight. With no enhancement, the rings would be essentially invisible in this mosaic. To improve their visibility, the dark (right) half of the rings has been brightened relative to the brighter (left) half by a factor of three, and then the whole ring system has been brightened by a factor of 20 relative to the planet. So the dark half of the rings is 60 times brighter, and the bright half 20 times brighter, than they would have appeared if the entire system, planet included, could have been captured in a single image.

The moon Janus (179 kilometres across) is on the lower left of this image. Epimetheus (113 kilometres across) appears near the middle bottom. Pandora (81 kilometres across) orbits outside the rings on the right of the image. The small moon Atlas (30 kilometres across) orbits inside the thin F ring on the right of the image. The brightnesses of all the moons, relative to the planet, have been enhanced between 30 and 60 times to make them more easily visible. Other bright specks are background stars. Spokes -- ghostly radial markings on the B ring -- are visible on the right of the image. This view looks toward the northern side of the rings from about 20 degrees above the ring-plane.
Data
Font NASA CICLOPS
Autor NASA/JPL/Space Science Institute
Altres versions JPL Photojournal

The image was taken about 1.25 days after exact equinox. Red, green and blue spectral filters of the wide angle camera and were combined to create this natural colour view. The image was obtained at a distance of approximately 847,000 kilometres from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 74 degrees. Image scale is 50 kilometres per pixel.

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Public domain Aquest fitxer és en el domini públic perquè ha estat creat per la NASA. L'avís legal de la NASA diu que «el material de la NASA no està protegit per copyright si no es diu el contrari». (NASA copyright policy page o JPL Image Use Policy).
Atenció:
  • L'ús dels logotips de la NASA, insígnies i emblemes està restringit la llei dels EUA 14 CFR 1221.
  • El lloc web de la NASA disposa d'un gran nombre d'imatges de l'Agència Espacial Russa, o soviètica, i d'altres agències no nord-americanes. Aquestes imatges no són necessàriament en el domini públic.
  • El material del Telescopi espacial Hubble pot tenir els drets reservats si no prové explícitament del STScI. [1]
  • Tot el material de la sonda SOHO està reservat i requereix d'autorització per a un ús comercial no educatiu. [2]
  • Les imatges destacades en el lloc web Astronomy Picture of the Day (APOD) poden tenir drets d'autor. [3]

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Data/horaMiniaturaDimensionsUsuari/aComentari
actual18:08, 7 juny 2014Miniatura per a la versió del 18:08, 7 juny 20147.227 × 3.847 (3,58 Mo)NH2501Lower compression, taken from http://www.dlr.de/media/en/desktopdefault.aspx/tabid-4986/8423_read-12880/8423_page-2
20:24, 21 set 2009Miniatura per a la versió del 20:24, 21 set 20097.227 × 3.847 (1.018 Ko)Originalwana{{Information |Description={{en|1=Seen from our planet, the view of Saturn's rings during equinox is extremely foreshortened and limited. But in orbit around Saturn, Cassini had no such problems. From

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