Astronomy I Crossword Puzzle

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