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Moon and Giants

June 5, 2010

Uranus is the third-largest planet in the solar system, yet most of us have never seen it. It's so far away that it's quite faint -- you need binoculars to pick it out.

But if you have binoculars, tomorrow presents a great chance to find this hidden giant. It's near Jupiter, which looks like a brilliant star to the lower right of the Moon at first light. From Jupiter, scan just a bit toward the Moon for a tiny blue-green "star."

Uranus has more than two dozen moons of its own. A few are interesting worlds in their own right.

The largest are Titania and Oberon -- names that come from Shakespeare's play "A Midsummer Night's Dream."

We've had just one clear view of these moons -- from the Voyager 2 spacecraft a quarter-century ago.

Titania's about a thousand miles in diameter. Voyager's pictures revealed big cracks on its surface that may be the result of motions beneath its crust. And bright features along the cracks could be frost -- perhaps indicating that Titania has a thin atmosphere.

The surface of Oberon appears to be older and less active. Its most interesting feature is a mountain that towers four miles above the moon's icy surface.

When Voyager flew past Uranus, though, much of the northern hemispheres of these worlds were in darkness. They just emerged into the sunlight a few years ago. So today, astronomers are watching these moons to see if they undergo any changes as their northern latitudes move into the light.

Script by Damond Benningfield, Copyright 2010

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