Moon and Saturn

StarDate: July 25, 2009

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The crescent Moon and the planet Saturn put on a nice display this evening. Saturn looks like a bright star to the Moon's right or upper right at nightfall.

Saturn's best-known feature is its rings -- broad, thin bands that encircle the planet.

Galileo Galilei was the first person to see the rings, in 1610. Through his crude telescope, though, they looked like "bumps" on the side of the planet. Since Galileo had already found several moons orbiting Jupiter, he surmised that Saturn's bumps were moons, too. When he looked again two years later, the bumps were nowhere in sight. But when they reappeared two years after that, Galileo concluded that they were "arms," not moons.

Their true nature was discovered by Dutch astronomer Christiaan Huygens. Using telescopes with a clearer view than Galileo's, he saw space between the structures and Saturn itself. In a book published 350 years ago this month, he wrote that they must be rings around the planet.

Today, we know that there are thousands of individual rings. They're made of small bits of ice and rock that orbit Saturn as tiny moons.

We also know why they temporarily "disappeared" from Galileo's telescope. As Saturn orbits the Sun, we see the rings at different angles. At certain times, we see them edge-on, so they all but vanish. And in fact, that's happening right now. So when you look at Saturn through a telescope, the rings appear as a thin but bright band around the giant planet.

Script by Damond Benningfield, Copyright 2009

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