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Saturn at Opposition

April 4, 2011

A giant world marches across the southern sky this week, shining like a golden beacon all night long.

Saturn is the second-largest planet in the solar system -- a gasbag of a world that's about nine times the diameter of Earth.

It probably consists of a rocky core surrounded by layers of hydrogen and helium, the two lightest chemical elements. So even though Saturn is huge, it's fluffy -- the planetary equivalent of cotton candy. And to keep the food theme going, it's topped by bands of clouds the color of butter or mustard.

Because the planet is a bag of gas, it's hard to measure the length of its day. There are no surface features to track because there's no solid surface. And the clouds are blown by high-speed winds, so you can't use them to track Saturn's rotation, either.

Instead, planetary scientists have had to use some trickier techniques to get at Saturn's day. They've measured radio waves produced by the planet's magnetic field -- waves that are synchronized to the planet's rotation. That technique has yielded the best measurements to date: about 10 and a half hours.

And coincidentally, right now that's about the amount of time that Saturn is in view in the night sky. It's low in the east as the sky gets good and dark, and looks like a bright golden star. It arcs across the south during the night. By the time it fades from view a little before sunrise, another full day will have spun by on this bright, fluffy planet.

Script by Damond Benningfield, Copyright 2011


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