Solar System - Higgins

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Across
  1. 4. Unit of measurement within the Solar System; average distance from Earth to the Sun. Abbreviated AU.
  2. 7. Planet with the coldest atmosphere in the Solar System.
  3. 9. Term that refers to the inner four planets.
  4. 10. Nebular clouds consist mostly of the gases hydrogen and ____.
  5. 14. Atmospheric gas which allows life to exist on Earth.
  6. 15. Planet which does NOT contain an atmosphere.
  7. 16. Bodies of water ice, frozen gases, rocks and dust which orbit the sun.
  8. 18. Rocky bodies that form from debris.
  9. 19. Third planet from the Sun.
  10. 20. Extremely bright, super-powerful exploding star.
Down
  1. 1. Object formed from dust, rock and materials which collide and join to form the infant stages of a planet.
  2. 2. First large planet to develop through the merging of icy planetesimals.
  3. 3. Our galaxy; includes the Solar System.
  4. 5. Force that draws matter together to form a star and possibly planets.
  5. 6. Region of the Solar System, between the orbits of Mars and Jupiter, that contain solid orbiting bodies.
  6. 8. An enormous interstellar cloud of dust and gas; nursery for new stars.
  7. 11. Earth's only natural satellite.
  8. 12. Once considered a planet; downgraded to a "dwarf planet".
  9. 13. Hottest planet in the Solar System due to its dense atmosphere.
  10. 17. How many natural satellites (moons) do the inner planets combined have?