Solar System

2. force by which a planet or other body draws objects toward its center
5. the time needed for one revolution
6. the belief that the sun was in the center of the solar system
7. a flattened nebula; shaped like a fried egg; thicker in the center; thin at the edge
9. property of matter that stays at rest or stays in motion until acted on by a force
11. point where a planet is closest from the Sun in its orbit
13. the belief that the Earth was in the center of the universe
14. the speed at which a planet revolves around a central more massive object
15. a large, thin cloud of gas and dust; spins when it was hit with the shockwave of a supernova
17. planets composed mostly of hydrogen or helium
18. backward motion of a planet
20. a curved path of an object as it revolves around a star, planet or moon
21. Law of Universal Gravitation (all objects attract due to gravity)
22. Laws that explain planetary motion

1. colliding and clumping of matter - due to gravity. Smaller pieces form larger pieces
3. point where a planet is farthest away from the Sun in its orbit
4. planets that have a compact, rocky surface
8. an oval shape
10. moon-sized planetesimals
12. the solar system formed from a solar nebula
16. an object in orbit (natural or human-made)
19. asteroid-like bodies combine (by colliding) to form initial planets