1. How all the stuff in the solar system was created

2. Step 1: Nebula forced out of balance by nearby supernova (probably) Step 2: Solar nebula forms, gravity pulls lighter elements toward center forming a protostar. 

3. Step 3: Protoplanetary disk, or accretion disk, flattens out due to rotation of protostar.

4. Step 4: Heavier elements stay close to sun and coalesce to form planetessimals, from gravity and heat from collisions. – Terrestrial planets form when gravity makes planetessimal round – Leftover heavy material forms asteroid belt.

5. Step 5: Sun’s fusion creates solar wind, which blows lighter elements (mostly hydrogen and helium) to outer solar system, creating four large “outer planets.” Sun’s energy doesn’t allow inner planets to be icy or gassy. Leftover, distant icy material forms the Oort cloud.

6. Formation of gas giant

7. The Oort cloud is spherical, while all else is flat. – It is the birthplace of comets

8. Distances and shapes of our solar system

9. What parts of the solar system will continue to change?