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

2. What would be the easiest way to increase the magnification of your telescope? a)Increase the size of the primary mirror b)Increase the size of the secondary mirror c)Use an eyepiece with a longer focal length d)Use an eyepiece with a shorter focal length e)There is no way, the magnification of a given telescope is fixed

3. Which of the following types of electromagnetic radiation are best studied from space? a)Ultraviolet b)Radio c)X-ray d)a and c only e)a, b, and c

4. 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 and Quizdom questions with no notes?  Bring pencil and calculator!  No sharing!

5. The Solar System  Questions   When did it form?   Why does it have structure?

6. Structure of the Solar System  The solar system has three distinct regions  Inner Region  Mercury, Venus, Earth, Mars, Asteroids   Outer region  Jupiter, Saturn, Uranus, Neptune and Moons   Trans-Neptunian region  Kuiper Belt and Oort Cloud 

7. 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

8. 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  Rapid rotation causes the outer layers to form a disk

9. Circumstellar Disks   We also can see them silhouetted against a bright background in Hubble images  Disks are common around young stars

10. From Disks to Planets  Many stars between 1-50 million years old have disks, but stars slightly older generally do not  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 

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

12. What Was the Solar Nebula Made of?  Solar Nebula --  From studying meteorites and star forming regions we hope to discover what the solar nebula was made of  Two basic components  Gas --  Dust -- made of rock (silicates), metal (iron) and ices (water, methane, ammonia, carbon dioxide)

13. Solar System Dust Grain

14. Accretion of Grains  Dust grains are very small (< 1 mm), how do they form planets?   If dust grains are fractal they may stick together more easily   At the end of this stage the solar system is populated by a few thousand planetesimals, such a system is invisible to telescopes

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

16. Temperature and the Solar Nebula  Two basic types of dust 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   Outer solar system -- icy planetesimals

17. Regions of Formation Temperature Rocky Icy Gas

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   No more hydrogen gas after a few million years  Thus, in the outer system where the temperatures are lower you have gas giants

20. Formation of Terrestrial Planets   Result is small rocky planets with no large gassy outer layers

21. Accretion of the Inner Planets

22. Orbital Evolution   This causes:  Shifting of the orbits of the Gas Giants   Icy planetesimals ejected to form the Kuiper Belt and Oort cloud

23. 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 

24. Steps in Solar System Formation 1Inner solar system -- volatiles boil off, resulting in small rocky planets 2Outer solar system -- large planet cores form rapidly from refractory and icy material, acquire large gas envelopes 3Edge of solar system -- leftover and ejected icy planetesimals form Kuiper belt and Oort cloud