In the course of Saturns trip around the Sun, it lifts its skirt of rings once every 29 years.
Instead of seeing Saturn's hoops edge-on, they appear, as shown in a recently released Hubble Space Telescope image, to open up, providing a fuller view that may help astronomers discern more about the composition, formation and fate of the rings.
The photos were taken with the Wide Field Planetary Camera 2, a camera that can obtain high resolution images over a relatively wide field of view.
How it works
Saturns equator is tilted at 27 degrees, much like Earth. And like Earth's tilt which causes the seasons to change by oscillating the hemispheres' position in relation to the Sun, Saturn's hemispheres and rings also oscillate. This process is shown starting from the lower left, during its 1996 northern autumnal equinox and follows the planet into 2000, when it was winter in the north and summer in the south.
"The brightness and color of the rings change as they open up," said Wellesley College astronomer Richard G. French, who helped collect the Hubble images. "These details tell us an awful lot about how theyre put together -- whether they're a thin sheet of ice or piled up on top of each other."
Astronomers do know that Saturns ruffle is made from chunks of dirty ice that vary in size anywhere from bits just a few centimeters wide to boulders several yards (meters) across. Their slight reddish color is from organic materials.
The ice chunks of the rings constantly collide, but Saturns gravity pulls them apart and prevents more moons from forming. Astronomers have discovered 18 moons around Saturn, making it the planet with the most moons in our solar system.
Mission to a flattened planet
Saturn is the second largest planet in our solar system -- only Jupiter is larger -- and, like its bigger neighbor, it is composed primarily of gas. With days lasting only 10 hours, the planet spins so fast that its poles are flattened. Strong winds pushing the atmosphere around show up as horizontal bands in the photos. Smog in the atmosphere gives the various color and brightness to these bands.
Hubble is helping astronomers prepare for the next mission to Saturn. In 2004, the Cassini/Huygens spacecraft, now en route, will arrive to orbit the gas giant for four years. It will also land the Cassini probe on the moon Titan, one of only a few places in our solar system that life may have formed.
"We hope that this long-term survey with the world's premier telescope over these past seven years will provide the foundation for planning the observations to be made when Cassini gets there," French said.
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