1. © 2004 Pearson Education Inc., publishing as Addison-Wesley Announcements Second Mid Term Exam Weds Mar 14 On energy, Newtons Laws, light, telescopes, the Solar System (including all material covered up to and including Fridays lecture) This weeks homework, due Mar 10 REMINDER: Telescope nights next Mon & Thurs rain or shine (unless UMBC closed) show up on Physics Building floor 4 room 401 at ~7:30 pm for ~ 1.5 hour session You only need go to one!!! Surnames A-M Mon Mar 12 Surnames N-Z Thurs Mar 15 OK, if you need to swap for the other night -don’t need to clear a swap with me These replace the lectures so no class Mon, Mar 12 or Friday Mar 16 and WEDs Mar 14 is the exam

2. 8. Welcome to the Solar System

3. © 2004 Pearson Education Inc., publishing as Addison-Wesley 8.1 Comparative Planetology What can we learn by comparing the planets to each other? Our goals for learning:

4. © 2004 Pearson Education Inc., publishing as Addison-Wesley Comparative Planetology Studying the similarities among and differences between the planets –this includes moons, asteroids, & comets This approach is useful for learning about: –the physical processes which shape the planets –the origin and history of our Solar System –the nature of planetary systems around other stars

5. © 2004 Pearson Education Inc., publishing as Addison-Wesley 8.2 The Layout of the Solar System What are the major patterns of motion in our solar system? What are the two major types of planet? Where do we find asteroids and comets in the solar system? Describe a few important exceptions to the general rules. Our goals for learning:

6. © 2004 Pearson Education Inc., publishing as Addison-Wesley The Layout of the Solar System Large bodies in the Solar System have orderly motions –planets orbit counterclockwise in same plane –orbits are almost circular –the Sun and most planets rotate counterclockwise –most moons orbit counterclockwise

7. © 2004 Pearson Education Inc., publishing as Addison-Wesley The Layout of the Solar System Pl anets fall into two main categories –Terrestrial (i.e. Earth-like) –Jovian (i.e. Jupiter-like or gaseous)

8. © 2004 Pearson Education Inc., publishing as Addison-Wesley Mars Neptune TerrestrialJovian

9. © 2004 Pearson Education Inc., publishing as Addison-Wesley

10. The Layout of the Solar System Swarms of asteroids and comets populate the Solar System

11. © 2004 Pearson Education Inc., publishing as Addison-Wesley

12. Oort cloud - immense spherical cloud surrounding planetary system - extends ~ 3 light years (30 trillion km) from Sun Largest structure falling under Sun’s sphere of influence Within it, comets exist …weakly bound to Sun …passing stars can change their orbits, sending them into inner solar system or out into interstellar space

13. © 2004 Pearson Education Inc., publishing as Addison-Wesley A Few Exceptions to the Rules… Both Uranus & Pluto are tilted on their sides. Venus rotates “backwards” (i.e. clockwise). Triton orbits Neptune “backwards.” Earth is the only terrestrial planet with a relatively large moon.

14. © 2004 Pearson Education Inc., publishing as Addison-Wesley The Sun – King of the Solar System How does the Sun influence the planets? –Its gravity regulates the orbits of the planets. –Its heat is the primary factor which determines the temperature of the planets. –It provides practically all of the visible light in the Solar System. –High-energy particles streaming out from the Sun influence planetary atmospheres and magnetic fields.

15. © 2004 Pearson Education Inc., publishing as Addison-Wesley What have we learned? What can we learn by comparing the planets to each other? We gain new insights into the physical processes that shape Earth and other planets, we learn about the origin and history of the solar system as a whole, and we learn to apply ideas from our solar system to other planetary systems. What are the two major types of planet? The small, rocky terrestrial planets and the large, hydrogen-rich Jovian planets.

16. © 2004 Pearson Education Inc., publishing as Addison-Wesley What have we learned? What are the major patterns of motion in our solar system? All planets orbit the Sun in the same direction and with nearly circular orbits in nearly the same plane. The Sun and most planets rotate in the same direction that they orbit. Most large moons orbit their planets in the same direction as well. Where do we find asteroids and comets in the solar system? Most asteroids reside in the asteroid belt between Mars and Jupiter. Comets are found in two main regions: the Kuiper belt and the Oort cloud.

17. © 2004 Pearson Education Inc., publishing as Addison-Wesley Outer planets…Pluto & Planet X Pluto was discovered in 1930 but remained an enigma for over 60 years because of its stark differences with the other planets. The discovery of the Kuiper belt in the mid-1990s revolutionized our view of the solar system and placed Pluto in its proper context. Pluto can now be viewed as the gateway to the debris disk beyond Neptune that is a leftover of the planetary formation process that terminated roughly 4 billion years ago.

18. © 2004 Pearson Education Inc., publishing as Addison-Wesley Outer planets…Pluto & other dwarf planets Pluto downgraded to “dwarf planet” designation

19. © 2004 Pearson Education Inc., publishing as Addison-Wesley A Brief Tour of the Solar System -- Motions

20. © 2004 Pearson Education Inc., publishing as Addison-Wesley What is density? density = mass/volume typical units: [ g/cm 3 ] Density of water is defined as 1 g/cm 3.

21. © 2004 Pearson Education Inc., publishing as Addison-Wesley A Brief Tour of the Solar System – Composition

22. © 2004 Pearson Education Inc., publishing as Addison-Wesley A Brief Tour of the Solar System – Summary

23. © 2004 Pearson Education Inc., publishing as Addison-Wesley Major Categories of Spacecraft Mission 1. Flyby – spacecraft “flies by” a world just once 2. Orbiter – spacecraft orbits the world it studies –longer-term study is allowed 3. Lander/Probe – spacecraft lands on the surface of the world or plunges through its atmosphere 4. Sample Return – spacecraft returns to Earth with a sample of the world it has studied These types of mission are listed in order of increasing cost.