Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2010 October 12
See Explanation.  Clicking on the picture will download
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Saturn: Light, Dark, and Strange
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

Explanation: What's creating those dark bands on Saturn? Sometimes it takes a little sleuthing to figure out the how and why of a picture taken by the Saturn-orbiting Cassini spacecraft. Let's see. That large orb on the left must be Saturn itself. Those arcs on the right are surely the rings. The dark band running diagonally must be the shadow of Saturn on the rings. That leaves the unusual dark bands superposed on Saturn's disk -- are they the shadows of the rings? A punctilious detective would conclude that they are not. If one looks carefully, the rings arc from behind the planet on the lower left, around to the right, and therefore must pass on the camera side of the planet on the upper left. So the rings themselves cause the dark streaks on Saturn. These rings segments appear dark because they are in the shadow of Saturn. The night part of Saturn shows a faint glow because of sunlight reflected from other parts of the rings. Got it? Unfortunately, if it weren't for the tile floor, tomorrow's picture would be even harder to understand.

Tomorrow's picture: virtuous patience

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