1. Nebular Theory of Solar System Formation

2. Learning Goals
Understand how the solar system formed Understand evidence proving the solar nebular theory

3. Solar Nebular Theory Summary

4. Solar System
1. All the orbits of the planets are prograde (i.e. if seen from above the North pole of the Sun they all revolve in a counter-clockwise direction/revolve west to east).
2. All the planets orbit in the same plane
3. Terrestrial planets are dense, rocky and small, while Jovian planets are gaseous and large.

5. Early Solar System
Stars and planets formed together from a low-density cloud of interstellar gas and dust called a nebula

6. Solar Nebular Theory
Gravity pulled this cloud of dust together and it created a hot dense object in the center called a protostar These clouds of dust particles ranged in size from a grain of sand to planet sized rocks The nebula started to collapse and rotate in a flat disk

7. Solar Nebular Theory: Sun
When the temperature reaches 10,000,000 Celsius, nuclear fusion begins and the protostar begins producing energy Enormous pressure and heat cause hydrogen atoms to combine to become helium atoms and light energy in the core

8. Solar Nebular Theory: Planets
Condensed grains from nebula collide and stick to form planetesimals These planetesimals grew by further collisions called accretion Gravity holds them together, when big enough some planetesimals eventually become very small planets.

9. Solar Nebular Theory: Planets II
As rotating nebular disk cooled, the only metals and rocks could condense near the sun Far away from the Sun ice large ice chunks were able to condense Ice clumps were able to get much more massive (since there was more of them); through gravitational pull, they were able to attract large amounts of nebular gas and become gas giants

10. Proof for the Nebular Theory
Many young stars in the Orion Nebula are surrounded by dust disks: Probably sites of planet formation right now!

11. Homework
Exit Card Describe two pieces of evidence that supports the Solar Nebular Theory