Tour of the Solar System

Learning Goal #16: I can analyze statistical data to compare and contrast objects in our solar system.

Guiding Questions:

  1. How do we measure and represent very large distances and sizes?
  2. What kinds of objects are found in our solar system?
  3. Compare and contrast the inner and outer planets.
    1. What features do the inner planets share?
    2. What features do the outer planets share?
  4. Where does Pluto belong in this classification system?

Before you embark on this tour, let’s review how scientists measure and represent large distances in space. What units are used to measure space distances? When might each unit be used?

  1. Kilometer

    • Used to measure small distances, such as within our solar system
      • The moon is 384,400 km from Earth
  2. Astronomical Unit (AU)

    • 1 AU = ~150,000,000 km
    • Equivalent to the distance from the Earth to the sun
    • Used to measure distances within our solar system
      • Pluto is 39.5 AU from the sun
    • AU
  3. Light Year (ly)

    • The distance light travels in one year
    • 1 ly = ~9.5 trillion km or 6 trillion miles
    • Used to measure distances outside of our solar system, such as to nearby stars or galaxies
      • The Andromeda galaxy is 2,538,000 light years away.
    • Light-year

      Light Year

  4. Parsec (pc)

    • Stands for “parallax of one arc second”
    • Used to measure distances outside of our galaxy
    • 1 parsec = 3.26 light years
    • 1 megaparsec = 1 million parcecs = 3.26 million light years
      • The distance to the nearest star, Proxima Centauri is 1.3 pc away.
      • The Virgo galaxy cluster is 16.5 mpc away.
    • parsec

The first stop as you leave planet Earth is our lovely satellite… Luna! Our moon is just one of many natural satellites in space. What are some other space objects you’ll encounter in the solar system?

There are a lot of objects in our solar system, including planets, moons, asteroids, meteoroids, and comets.


  • moons of ss


  • Asteroids are rocky metallic objects that orbit the sun, ranging in size from dust particles to nearly dwarf planets
  • Often irregularly shaped due to the weak amount of gravity
  • Tens of thousands exist in our solar system, located primarily in Asteroid Belt between Mars and Jupiter
  • NASA Asteroids Page
  • Brainpop: Asteroids

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  • Small pieces of rock & debris that orbit the sun, possibly pieces of asteroid or comet
  • They become meteors – or shooting stars – when they fall through a planet’s atmosphere and leave a bright tail
  • Sometimes, larger meteors cause a bright flash called a fireball.
  • Meteorites are smaller pieces that survive the journey to hit the ground
  • Most weigh only a few pounds & cause little damage. Occasionally, large ones reach Earth and cause damage
  • NASA Meteor & Meteorites


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  • Cosmic snowballs of frozen gases, ice, rock and dust
  • Roughly the size of a small town… or downtown LA…
  • When a comet’s orbit brings it close to the sun, it heats up and spews dust and gases into a giant glowing head larger than most planets.
  • The dust and gases form a tail that stretches away from the sun for millions of kilometers.
  • NASA Comets
  • Brainpop: Comets


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Next stop, the inner planets. What are the four inner planets and what features do they share? 


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Before traveling to the outer planets, you pass through the asteroid belt. What are some common misconceptions about asteroids and the asteroid belt?

You finally reach the outer planets! What are the four outer planets and what features do they share?

Keep going a little farther and you visit poor Pluto. In 2006, the International Astronomical Union (IAU) downgraded Pluto from a planet to a dwarf planet. Do you agree with this classification, or do you feel that Pluto is best classified as something else? Explain.


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On the way out of the solar system, you encounter two more regions. First, you pass through the Kuiper Belt. After that, you bust through the Oort Cloud. What is important about these regions?


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Additional Resources