8.1 Exploring Our Solar System

You probably learned we once had nine planets in our Solar System.  Now we have only eight!  What happened?  Astronomers from all over the world had a meeting to decide on the definition of a planet.  When they were finished Pluto was no longer considered to be a planet.  It is now called a dwarf planet. 
Watch the Space School Pluto video to find out more about Pluto and its reclassification from planet to dwarf planet.  You will use the video to help you answer the questions that follow. You may pause the video to record your answers. You should also make sure the Close Captioning (CC) button is turn on.

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When was Pluto first discovered?

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When was Pluto reclassified as a dwarf planet?

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What are the three rules to be classified as a planet? List them below.

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What rule does Pluto not follow?

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According to scientist, Pluto is composed mostly of

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The surface of Pluto is composed almost entirely of

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Pluto has strong gravity.

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Pluto is one of the coldest planets in our universe.

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Look at the picture above. These are dwarf planets from our solar system compared to the Earth’s moon. How does Pluto’s size compare to our moon?

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When was Pluto first discovered?

When was Pluto reclassified as a dwarf planet?

What are the three rules to be classified as a planet? List them below.

What rule does Pluto not follow?

According to scientist, Pluto is composed mostly of

The surface of Pluto is composed almost entirely of

Pluto has strong gravity.

Pluto is one of the coldest planets in our universe.

Look at the picture above. These are dwarf planets from our solar system compared to the Earth’s moon. How does Pluto’s size compare to our moon?

Which of these dwarf planets is larger than Pluto? (Ignore the negative sign in front of the numbers.)