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Dwarf Planets

Dwarf planets, including Pluto, are like planets except they have not cleared their orbits of debris.

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The Frost Line

The Frost Line

Credit: NASA
Source: http://commons.wikimedia.org/wiki/File:Ceres_optimized.jpg
License: CC BY-NC 3.0

Ceres is a dwarf planet covered by a dusty regolith (outer soil layer). No one is quite sure what is beneath that dust. The answer to the question may help astronomers to understand something about the early solar system.

Why It Matters

  • The placements of the planets in our solar system led scientists to an idea.
  • The hot sun drove off the ices and gases when the inner planets formed. Further out in the solar system, cooler temperatures allowed gases and ices to exist.
  • The result is that the rocky planets are near the sun and the gas giants are further out.
  • Credit: NASA
    Source: http://commons.wikimedia.org/wiki/File:Solar_system.jpg
    License: CC BY-NC 3.0

    Planets in order of distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune [Figure2]

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With the links below, learn more about the frost line. Then answer the following questions.

  1. Why didn’t the solar system cool uniformly? How did it cool instead?
  2. What is the frost line?
  3. Why do scientists want to know what is beneath the dusty regolith of Ceres?
  4. Comet ISON came from the far outer reaches of the solar system. When it got to the sun, it broke apart. What do you think the comet was made of and why did it break apart?

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Image Attributions

  1. [1]^ Credit: NASA; Source: http://commons.wikimedia.org/wiki/File:Ceres_optimized.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: NASA; Source: http://commons.wikimedia.org/wiki/File:Solar_system.jpg; License: CC BY-NC 3.0

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