Saturn at Opposition
Saturn is putting on its best face this month. The planet is at a point in its orbit called opposition, where it lines up opposite the Sun. It rises at sunset and remains visible all night. It's closest to Earth for the year, too, so it shines brightest -- brighter than all but a handful of true stars.
Saturn is best known for its rings, which are wider than the distance between Earth and the Moon. The Cassini spacecraft, which has orbited Saturn since 2004, has found that there are thousands of individual rings. Several small moons orbit inside the rings. They act as gravitational "shepherds," keeping the rings in place.
Some of the rings consist almost entirely of ice, while others also contain chunks of rock, plus lots of dust. When viewed at their greatest tilt, the rings can double Saturn's brightness. But this year we're starting to see the rings more nearly edge-on, so they don't add quite as much to Saturn's luster.
The rings may have formed fairly recently -- within the last hundred million years or so -- when a small moon or a wandering comet passed too close to Saturn and was pulled apart by the planet's strong gravity. But some of Cassini's observations hint that the rings may be as old as Saturn itself -- four and a half billion years.
Look for Saturn low in the east at nightfall. It looks like a bright star. The true star Regulus stands to its upper right. They soar high overhead during the night.
Script by Damond Benningfield, Copyright 2007
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