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'Bumpy' Saturn

July 30, 2010

By the summer of 1610, the great Italian astronomer Galileo Galilei had found wonders galore. Using his first crude telescopes, he'd discovered that the planet Venus shows phases, just as the Moon does; that moons orbit the planet Jupiter; and that the surface of our own Moon is rugged and uneven.

And 400 years ago today, Galileo wrote of yet another wonder: he'd seen "bumps" on the sides of the planet Saturn. He wrote that through his telescope, the planet looked "triple bodied...not a single star, but three together, which almost touch each other." Galileo suspected that he'd discovered two large moons orbiting the planet.

What he'd really discovered were Saturn's rings, but the view through his telescope wasn't clear enough for him to discern their true nature. In fact, Galileo was perplexed when he looked at Saturn two years later, and the bumps had disappeared. That was because the rings had turned almost edge-on to Earth, so they were too thin for his telescope to see.

Galileo never knew what he'd really discovered, because astronomers didn't discern the true nature of the rings until almost a half-century later -- long after Galileo's death.

Saturn is in good view tonight. It teams up with two other planets low in the west in early evening. Venus is the brightest of the three -- it's the "evening star." Saturn and Mars look like fainter stars to the upper left of Venus, with Saturn a little above Mars.

Script by Damond Benningfield, Copyright 2010

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