Gale
08-08-2009, 07:50 AM
Fascinating ... every 15 years Saturn's rings briefly disappear.
"Saturn has been performing the "ring plane crossing" illusion about every 15 years since the rings formed, perhaps as long as 4.5 billion years ago, so by now it is pretty good at it," said Spilker. "The magician's tools required to perform this trick are pure sunlight, a planet that wobbles, and a main ring system that may be almost 200-thousand miles wide, but only 30 feet thick."
All planets in our solar system wobble on their axes to some extent. This change of attitude eventually places a planet's equator directly in line with the photons of light streaming in from the sun. This is called "equinox," and on Earth it occurs every year about March 21 (spring equinox) and Sept. 22 (autumnal equinox). On Saturn, it occurs twice during each 29 Earth-year-long orbit around the sun (about every 15 years).
"Whenever equinox occurs on Saturn, sunlight will hit Saturn's thin rings, the ring plane, edge-on," said Spilker."The light reflecting off this extremely narrow band is so small that for all intents and purposes the rings simply vanish."
Saturn to Pull Celestial Houdini on Aug. 11 (http://saturn.jpl.nasa.gov/news/cassinifeatures/feature2009087/)
"Saturn has been performing the "ring plane crossing" illusion about every 15 years since the rings formed, perhaps as long as 4.5 billion years ago, so by now it is pretty good at it," said Spilker. "The magician's tools required to perform this trick are pure sunlight, a planet that wobbles, and a main ring system that may be almost 200-thousand miles wide, but only 30 feet thick."
All planets in our solar system wobble on their axes to some extent. This change of attitude eventually places a planet's equator directly in line with the photons of light streaming in from the sun. This is called "equinox," and on Earth it occurs every year about March 21 (spring equinox) and Sept. 22 (autumnal equinox). On Saturn, it occurs twice during each 29 Earth-year-long orbit around the sun (about every 15 years).
"Whenever equinox occurs on Saturn, sunlight will hit Saturn's thin rings, the ring plane, edge-on," said Spilker."The light reflecting off this extremely narrow band is so small that for all intents and purposes the rings simply vanish."
Saturn to Pull Celestial Houdini on Aug. 11 (http://saturn.jpl.nasa.gov/news/cassinifeatures/feature2009087/)