Across
- 7. when one object orbits another
- 9. the distance from a star where liquid water can exist
- 11. these planets are small and dense
- 12. a piece of ice that has a tail and orbits the sun
- 13. mass divided by volume
Down
- 1. the force responsible for the formation of our solar system
- 2. the shape of a planet's orbit
- 3. when an object spins on an axis
- 4. these planets are farther from the sun and larger
- 5. an object that orbits a planet
- 6. the sun is at the center of the solar system
- 8. a rock that hits the surface of a planet
- 10. chunks of rock that orbit the sun