Across
- 3. the relative size of things
- 4. the border between light and dark on the Moon
- 5. a planet outside our solar system
- 7. an object, diagram, or computer program that helps us understand something by making it simpler or easier to see
- 8. something we observe to be similar over and over again
Down
- 1. a moon outside our solar system
- 2. the amount of time it takes for a planet to complete one orbit around a star or stars
- 3. the star that is the main source of light at the center of our solar system
- 6. when the Moon is completely dark