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Planets of the Solar System

The eight planets of the solar system with increasing distance from the sun have larger orbits.

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Pluto's Identity Crisis
Teacher Contributed

Pluto’s Identity Crisis

Is Pluto a planet? A dwarf planet? A plutoid?

It seems as if Pluto’s official title is once again up in the air! In 2006, astronomers from around the world decided at the International Astronomical Union’s meeting to reclassify Pluto as a dwarf planet because it did not have gravitational dominance over its area in space. This decision made big waves in the scientific community as well as the larger general public. Pluto had always been defined as a planet and now that was changing. What was next? Is the Earth not round after all? It appears that there is still a lot about Pluto that we do not know. In July 2012, images of Pluto came back from Hubble Space Telescope with a new moon, labeled in the photo below as P5. Check it out:

Because of this newly identified moon, again Pluto’s status is being questioned? Does this mean that Pluto now can be considered a planet? Not according to scientists, but that will not stop the public from voicing their opinions: http://news.discovery.com/space/pluto-doesnt-have-to-be-a-planet-to-be-interesting.html

What do you think? How should we define a planet? How should we classify Pluto?

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  1. In order to accurately understand the situation, here is a little data on dwarf planets from NASA: http://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwarf
    1. How is a dwarf planet different from a regular planet?
    2. What is a plutoid?
    3. Why is Ceres not considered a plutoid?
  2. Use this interactive to further explore Pluto and gather evidence: http://science.nationalgeographic.com/science/space/solar-system/dwarf-planet/
  3. What do you think? How would you classify Pluto?
  4. As we explore further in our solar system and out into the universe, do you think that our definition and classification of Pluto as a dwarf planet will become more or less clear? Why?

Resources Cited

Discovery News. http://news.discovery.com/space/pluto-doesnt-have-to-be-a-planet-to-be-interesting.html

NASA. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwarf


National Geographic. http://science.nationalgeographic.com/science/space/solar-system/dwarf-planet/

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