1. Chapter 12: Dwarf Planets and Small Solar System Bodies

2. Pluto: distant ice world that was once a planet

3. Pluto was discovered by Clyde Tombaugh in 1930 Percival Lowell made calculations on the orbit of Neptune and predicted a 9 th planet. His calculations were based on flawed data, there is no 9 th planet.

4. Pluto’s moon Charon was discovered by James Christy in 1978

5. Pluto and Charon are tidally locked on each other Just as we only see one side of our moon from Earth, Pluto only sees one side of Charon. Since Pluto is also tidally locked, Charon also only sees one side of Pluto.

6. Four more moons have been discovered around Pluto

7. Pluto, Charon, Nix and Hydra are not very large

8. Pluto Has An Atmosphere!

9. The New Horizons mission is on its way to Pluto. It will fly by in 2015

10. Eris is the reason Pluto isn’t a planet anymore

11. There are a number of “large” Kuiper Belt Objects

12. There are now 5 Dwarf Planets

13. Ceres has been promoted from asteroid to dwarf planet Ceres was called a planet when it was discovered in 1801 but it was later demoted when we started to find lots of other objects in the asteroid belt

14. The Debris of the Solar System Asteroids and comets are leftover planetesimals. We don’t see the icy planetesimals until the fall in to the inner part of the system solar

15. When a piece of an asteroid comes close to Earth it may become a meteor

16. Meteoroids, Meteors and Meteorites NEO 1994 XM 1 Leonid Meteor Shower

17. Big rocks DO fall from the sky! Fortunately for us, they don’t do it too often

18. A bad day for the dinosaurs

19. The impact released trillions of tons of CO 2 into the atmosphere The crater is buried several hundred meters under the surface and is over 200 km in diameter

20. Fortunately, most impacts are small The Peekskill meteorite fell in 1992 and hit an 1980 Chevy Malibu. Insurance wouldn’t pay for the damage but she got $10k for the car and $69k for the meteorite from a collector.

21. Meteorites are classified as Stones, Irons or Stony-irons

22. The most common meteorite, stones look like ordinary rocks with burnt crust

23. The most common “find” is an iron meteorite

24. Widmanstätten Patterns are iron crystals that take millions of years to form The iron has to cool from the molten state at no more than a few degrees every million years to form these crystal patterns

25. Stony-Irons are intermediate between stones and irons

26. Carbonaceous chondrites are from the earliest age of the solar system They show the original condensation grains from the solar nebula period when they formed

27. The different types of meteorites implies different types of parent asteroids Some asteroids have a lot of carbon materials. These are known as C-type asteroids

28. S-type and M-type asteroids are from differentiated bodies

29. To form S-type and M-type asteroids a larger body must be smashed to pieces

30. Most (but not all) asteroids orbit between Mars & Jupiter

31. The Apollo, Aten and Amor asteroids cross Earth’s orbit

32. Most asteroids are small and irregular shaped

33. Asteroids tumble Most have rotational periods of 9 to 10 hours

34. Some asteroids are piles of debris 253 Mathilde

35. We have landed on one asteroid: Eros

36. Comets are the debris of the Outer Solar System

37. Many comets come from the Kuiper Belt The Kuiper Belt is a thick donut shaped region extending from about 30 AU out to 50 AU. Pluto and Eris are the largest known Kuiper Belt objects

38. Some comets come from the Oort Cloud The Oort Cloud may extend out to a lightyear (50,000 AU) from the Sun

39. When a comet approaches the inner solar system the ice evaporates

40. The gas and flaked off dust form a coma and tail

41. A comets tail always points away from the Sun There are two tails: a dust tail that trails behind some and an ion tail that always points directly away from the Sun

42. Comet tails can be millions of kilometers long

43. The tail can break off due to “gusts” in the solar wind

44. Comet orbits are tilted from the ecliptic and very eccentric

45. What happens to comets?

46. Comets “die” in one of three ways 1: They fall in to the Sun They don’t have to actually fall into the Sun, just get close enough to burn up

47. 2: They collide with a planet or moon Shoemaker-Levy 9 had a amazing collision with Jupiter in 1994

48. Will a comet ever hit us? The highest rated object is rated a little below 1

49. We were probably hit by a fragment of a comet in 1908 The Tunguska event flattened over 800 square miles of forest in Siberia. It was probably an object about the size of a football field that exploded about five miles above the surface

50. 3: They break-up and fizzle out

51. Meteor Showers come at regular times of the year

52. Meteor Shows are the result of Earth passing through a debris trail left by a comet

53. Usually, meteor showers are a few dozen to a few hundred per hour

54. On rare occasions there are meteor storms The 1833 Leonid meteor storm

55. Most of the stuff floating around out there is dust sized Most of the dust is flaked off from comets and burns up in the atmosphere before reaching the ground

56. There is so much dust in the ecliptic we can see its glow It’s called the Zodiacal Light because it lies along the ecliptic which is the line of the zodiac