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