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Saturn is known for its beautiful rings, and its moon Titan, which may have liquid water.

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Is Phoebe a Planet?

Is Phoebe a Planet?

Credit: NASA/JPL/Space Science Institute
Source: http://en.wikipedia.org/wiki/File:Phoebe_closeup_cassini_NASA.jpg
License: CC BY-NC 3.0

Remember all the things a planet has to be? It has to: orbit a star, be spherical, not be a star itself, and have cleared its orbit of debris. Could Saturn’s moon Phoebe be a planet? Let’s count the ways (it isn’t).

Amazing But True!

Credit: NASA/JPL-Caltech/SSI/Cornell
Source: http://en.wikipedia.org/wiki/File:Phoebe_contour_map_PIA15507.jpg
License: CC BY-NC 3.0

Stripped of its impact craters, Phoebe was once spherical, or nearly so [Figure2]

  • Astronomers aren’t really suggesting that Phoebe is a planet, but it’s not like Saturn’s other moons either.
  • Scientists have reconstructed its impact history and determined that its shape was nearly spherical.
  • Phoebe is one of more than 60 moons of Saturn.

Can You Apply It?

With the links below, learn more about Saturn’s moon, Phoebe. Then answer the following questions..

  1. What are the reasons that Phoebe is not a planet?
  2. How is Phoebe not like the other moons of Saturn?
  3. How could Phoebe have been nearly spherical in the beginning?
  4. Where do scientists think Phoebe originated and why?
  5. How did Phoebe become a moon of Saturn?
  6. Do you think that the other moons of Saturn have a similar history to Phoebe’s? Why or why not?

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Image Attributions

  1. [1]^ Credit: NASA/JPL/Space Science Institute; Source: http://en.wikipedia.org/wiki/File:Phoebe_closeup_cassini_NASA.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: NASA/JPL-Caltech/SSI/Cornell; Source: http://en.wikipedia.org/wiki/File:Phoebe_contour_map_PIA15507.jpg; License: CC BY-NC 3.0

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