Explanation:
Saturn at Equinox!
Until last month, it was not clear what Saturn’s rings would look like when they pointed directly at the Sun. Every 15 years, as observed from Earth, the rings seem to disappear when they point toward Earth. Now, the disappearing rings are no longer a mystery; we know the rings are very thin, and Earth is so close to the Sun that when the rings point directly at the Sun, they are also edge-on to Earth. Fortunately, in the third millennium, humans can use spacecraft to observe Saturn at equinox directly from the side. Last month, the Cassini spacecraft captured a series of images of Saturn at equinox. The image above combines 75 frames, where the rings appear unusually dark and cast a very thin shadow on Saturn’s cloud tops. Particles being brightly illuminated create long shadows on the ring plane. Examining these images helps in understanding the particle dynamics and orbital motion of objects like the particles in Saturn’s rings.
Translation from:
NASA Website:
http://antwrp.gsfc.nasa.gov/apod/astropix.html
http://antwrp.gsfc.nasa.gov/apod/ap090930.html
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