First Semester

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Across
  1. 5. Limits of a system
  2. 6. Something that makes a system operate
  3. 10. Gases surrounding a planet
  4. 12. Length of time an object goes around another object
  5. 14. Interacting parts working together
  6. 17. Spinning on an axis
  7. 18. Three dimensional round object
  8. 20. A scientist who defined the laws of gravity
Down
  1. 1. Solid surface
  2. 2. Half of a sphere
  3. 3. Livable
  4. 4. Planet made of gas
  5. 7. One of four strong forces
  6. 8. Planetary object
  7. 9. Orbiting sphere with its own path around a star
  8. 11. System Planets orbiting a star(s)
  9. 13. the line or point on which an object turns
  10. 15. At the center of a solar system
  11. 16. Celestial body orbiting a planet
  12. 19. An imaginary line between the northern and southern hemispheres