Across
- 1. our galaxy
- 5. a theory explaining how the universe began
- 7. a ball of ice and rock that forms a long tail near the sun
- 9. the force of attraction between objects in the universe
- 10. defined as "an object in motion will stay in motion unless acted upon by an outside force"
- 13. the orbiting of bodies around a star
- 16. a meteoroid that enters our atmosphere
- 17. the process of forming helium from hydrogen in stars
- 19. any object observed in the sky
- 20. color shift exhibited by objects moving towards us
- 21. planets that are rocky and found closer to our sun
Down
- 2. the brightness of a star relative to our sun
- 3. consists of our sun and the objects orbiting around it
- 4. the shape of planetary orbits around the sun
- 6. gas giants
- 8. a collection of billions of stars, dust, and gases held together by gravity
- 11. a large ball of gas held together by gravity that gives off energy
- 12. everything
- 14. color shift exhibited by objects moving away from us
- 15. the apparent change in frequency of light or sound as the source moves towards or away from the observer
- 16. a body orbiting a planet
- 18. a small, rocky body orbiting the sun; many are found in a belt between Mars and Jupiter