Formation of the Solar System

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Across
  1. 5. person who first proposed the nebular theory
  2. 6. Mercury, Venus, Earth, and Mars are classified as this kind of planet
  3. 8. this movement made the solar nebula spin faster
  4. 12. when a nebula is flattened by spinning and gravity
  5. 14. Jupiter and Saturn are classified as this kind of planet
  6. 16. these planets form before the inner planets
  7. 18. once a protoplanet has accumulated enough material to reach a certain size it becomes this
  8. 19. Uranus and Neptune are classified as this kind of planet
  9. 20. a contracting mass of gas which represents the step before a star is born
Down
  1. 1. when rocky, solid, or metal particles accumulate and stick together
  2. 2. it is believed that this planet most likely formed first
  3. 3. when icy or gaseous particles accumulate and stick together
  4. 4. the force that causes the solar nebula to shrink and heat up
  5. 7. the step that comes after planetesimal and before planet
  6. 9. theory that states our solar system formed from the collapse of a solar nebula
  7. 10. the celestial body whose explosion & resulting shockwave triggered the solar nebula to collapse
  8. 11. rocks from this celestial body provide proof of the nebular theory
  9. 13. massive rotating cloud of gas and dust
  10. 15. small, irregularly shaped bodies
  11. 17. a protostar turns into this once it is hot enough for nuclear fusion to occur