Starship Asterisk*

Happy Saturn equinox day!

http://antwrp.gsfc.nasa.gov/apod/ap080921.html
http://antwrp.gsfc.nasa.gov/apod/ap050726.html
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http://www.planetary.org/blog/article/00002041/

Titan's shadow on Saturn near equinox

<<This photo was taken by Cassini on August 4, 2009, just a week before Saturn's equinox. Sunlight strikes Saturn's rings almost perfectly edge-on, making their shadow on Saturn an incredibly thin line along the equator. The rings are dark, illuminated almost only by light reflected off of Saturn, except for the F ring, whose dusty particles scatter light to Cassini's cameras. The shadow of Titan crosses the rings and forms a dark blob on Saturn's equator. Because the rings are lit by Saturnshine, not sunshine, Titan's shadow isn't visible on the ring system except where it crosses the F ring, which is lit up by sunlight. A relatively long exposure was required to capture detail in the rings, so Saturn's sunlit areas are overexposed; some "pixel bleeding" results from the overexposure. Credit: NASA / JPL / SSI>>
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Saturn's Rings to Disappear Tuesday - 2009 August 11

In a celestial feat any magician would appreciate, Saturn will make its wide but thin ring system disappear from our view Aug. 11.

Saturn's rings, loaded with ice and mud, boulders and tiny moons, is 170,000 miles wide. But the shimmering setup is only about 30 feet thick. The rings harbor 35 trillion-trillion tons of ice, dust and rock, scientists estimate.

The rings shine because they reflect sunlight. But every 15 years, the rings turn edge-on to the sun and reflect almost no sunlight.

"The light reflecting off this extremely narrow band is so small that for all intents and purposes the rings simply vanish," explained Linda Spilker, deputy project scientist for the Cassini Saturn mission at NASA's Jet Propulsion Laboratory.

Revelations in Saturn's rings continue as equinox approaches

The equinox lowers the Sun's angle to the ring plane and causes out-of-plane structures to cast long shadows across the rings' broad expanse, making them easy to detect.

Thanks to a special play of sunlight and shadow as Saturn continues its march towards its August 11 equinox, recent images captured by NASA's Cassini spacecraft are revealing new three-dimensional objects and structures in the planet's otherwise flat rings.

Through the detections of shadows cast upon the rings, a moonlet has been spotted for the first time in Saturn's dense B ring and narrow vertical structures are seen soaring upward from Saturn's intricate F ring.