1. Origin of the Solar System Astronomy 311 Professor Lee Carkner Lecture 8

2. Quiz 1 Monday  Covers lectures 1-8 and associated readings  About half multiple choice (~20 questions), half short answer/problems (~4 questions)  Study:  Notes  Can you write a paragraph explaining each major concept?  Exercises  Can you solve all the exercises with no resources?  Readings  Can you do all the homework with no book?  Bring pencil and calculator!  No sharing!

3. The Solar System  The solar system is not just a random collection of planets  The solar system has a structure  

4. Where Did the Solar System Come From?   We can’t look back in time to see how the Sun and planets formed, but we can look at young stars that are forming today

5. Star Formation  Stars are formed in clouds of gas and dust when a clump of material starts to contract  The mutual gravity of the particles in the clump causes the contraction to continue   Conservation of angular momentum makes the clump spin faster 

6. Star Formation in Action

7. Star Formation in Orion

8. Protoplanetary Disks in Orion

9. Protostellar Jet

10. Circumstellar Disks  Disks are fairly cool and can be detected with infrared and millimeter telescopes   Disks are common around young stars

11. From Disks to Planets   Where does the disk go?   A disk has more surface area than a group of planets with the same mass, so it radiates more light

12. How Do Planets Form?  There are 4 stages to planet formation 11 22 33 4  gas and leftover planetesimals are cleared from solar system

13. What Was the Solar Nebula Made of?  Solar Nebula -- Initial disk of material that the solar system formed from   Two basic components  Gas --  Dust --

14. Solar System Dust Grain

15. Accretion of Grains  Dust grains are very small (< 1 mm), how do they form planets?  Grains get larger by sticking together and settle to the center of the disk   Eventually the grains form into larger bodies (a few km in size) called planetesimals 

16. Accretion in a Protoplanetary Disk Star Disk High Density Low Density Larger Grains move to center

17. Temperature and the Solar Nebula  Two basic types of material in solar nebula:  Volatiles --  Refractory Material --  Temperatures were higher in the inner solar system and lower in the outer solar system  Near the Sun the volatiles boiled off leaving only the refractory material behind  Inner solar system --  Outer solar system --

18. Planetesimals to Planets  Due to gravity and intersecting orbits the planetesimals collide with each other   Planet formation happens differently in inner and outer solar system

19. Formation of Gas Giants  In the outer solar system you have more material (both volatiles and refractory material), so planets are larger    Thus, in the outer system where the temperatures are lower you have gas giants

20. Formation of Terrestrial Planets  In the inner solar system planets grew more slowly out of less material, most of it refractory 

21. Accretion of the Inner Planets

22. Beyond the Gas Giants  Beyond Neptune the densities are so low and the orbital timescales are so long no planets form at all   Other icy planetesimals are ejected by a close encounter with Jupiter or another gas giant 

23. Cleaning Up  Some of the material in the solar nebula does not end up in the final solar system   The solar wind will eventually blow most of the unaccreted gas and small particles out of the system

24. The Final Solar System  Our picture of planet formation is driven by an attempt to explain our own solar system and its three regions   Outer or Gas Giant region   We have also found other types of planetary systems different from our own 

25. Regions of Formation Temperature Rocky Icy Gas

26. Building the Solar System  By looking at stars with protoplanetary disks and the structure of our own solar system and we can develop a theory of how planetary systems form   Our current picture of planet formation explains the 3 regions of the solar system

27. Step by Step 1Inner solar system -- 2Outer solar system -- large planet cores form rapidly from refractory and icy material, acquire large gas envelopes 3Edge of solar system --