Not Your Parents’ Solar System!

1. Not Your Parents’ Solar System! Frank Summers Space Telescope Science Institute NSTA Institute Symposium November 15, 2003

2. How I learned the solar system • Sun & 9 planets • Separate section on each • Mention asteroids and comets • Lots of cool facts

3. Mercury My Venus Very Earth Energetic Mars Mother Jupiter Just Saturn Served Uranus Us Neptune Nine Pluto Pizzas

4. What’s wrong? • Memorization • Factoids • Highlights differences • Little or no relevance • Little or no “big picture”

5. An Improvement • Compare and contrast • Discuss broad ideas • Apply to planets, moons, etc., as a group • Highlight similarities • Appearance • Characteristics • Events

10. Other comparisons • Craters – Earth, Moon, Mercury, etc • Volcanoes – Mount St. Helens, Olympus Mons, Io, etc • Canyons – Grand Canyon, Mariner Valley • Storms, Winds, Seasons, Weather, Ice Floes, Magnetic Fields, Moons, Rings, etc

11. Compare and Contrast • Messages • What happens on Earth happens elsewhere • Solar system is understandable • Problems • Need to establish facts before comparison • Big picture still lacking

12. 21st Century View • Six families of the solar system • Star • Rocky planets • Asteroid belt • Gas giant planets • Kuiper belt • Oort cloud

16. Hollywood’s View of the Asteroid Belt

17. 500 million miles Thousands of asteroids … about a million miles apart! Scientific View of the Asteroid Belt

20. Kuiper Belt

21. Oort Cloud ? • Billions of icy minor planets – comet nuclei • Roughly spherical out to 50,000 AU • Predicted by Jan Oort • Explains long-period comets • No observations

22. Families of the Solar System • Classes of similar objects • Size • Composition • Orbit size • Orbit shape • Orbit inclination • Moons • Rings

23. Families of the Solar System • Classification • Structure of the solar system • Similar objects lie in similar regions • Clues to solar system formation and evolution

25. Sun Rocky Planets Asteroid Belt Gas Giant Planets Kuiper Belt Oort Cloud

26. Sun Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Kuiper Belt Oort Cloud

27. Some May View Elaborate Mnemonics As Boring, Just Some Useless Nonsensical Knowledge, But Others Cheer

28. What about Pluto? • Not a rocky planet • Not a gas giant planet • For teachers, it is an opportunity

29. Planet Pluto • 1930 Tombaugh discovers Pluto

30. Double Take: Charon • 1978 – James Christy (USNO) observations to refine Pluto’s orbit • Notices elongated images, deduces moon • 1985 – Charon occults Pluto, confirms existence • Refined sizes and masses – tiny

31. First Pictures of Pluto/Charon • 1995 – Hubble Space Telescope infrared • 1996 – Hubble Space Telescope visible

32. First Pictures of Pluto

34. Black Sheep of the Planets • Pluto is the oddball • Size • Companion • Composition • Orbit • 3:2 resonance with Neptune • Pluto/Charon as double ice planet?

35. Kuiper Belt • History • 1930 – Leonard mentions possibility of trans-Plutonian objects • 1943 – Kenneth Edgeworth postulates objects beyond Pluto • 1951 – Gerard Kuiper predicts that a massive Pluto would disperse small objects into a belt • 1980 – Fernandez predicts belt that resembles what was eventually found

36. KBOs • 1992 – Jewitt & Luu find object dubbed QB1 • Distance of 42 AU • First (third?) object discovered in the Kuiper Belt

37. More and more KBOs • Large searches for KBOs ensued • Hundreds discovered within a decade • Over 600 so far (Nov 2003) • Over 70,000 predicted with diameters > 100 km, orbits 30-50 AU • Plutinos – Neptune resonance • Scattered – Neptune affects orbit • Classsical – Separated from Neptune

41. Pluto/Charon orbits within Kuiper Belt

42. Large KBOs • Pluto still larger, but not by that much • Note: plot below doesn’t include Quaoar

44. Binary KBOs • Pluto/Charon not the only binary object • Nine discovered so far (Nov 2003) • All types of KBOs have binaries

46. What is Pluto? • You make the call • Singular ice planet • Mutant giant double comet • King of the Kuiper Belt • ???

47. Kuiper Belt Expert’s View “So, bluntly put, one has two choices. One can either regard Pluto as the smallest, most peculiar planet moving on the most eccentric and most inclined orbit of any of the planets or one can accept that Pluto is the largest known, but otherwise completely typical, Kuiper Belt Object. The choice you make is up to you, but from the point of view of trying to understand the origin and significance of Pluto it clearly makes sense to take the second option.” Dave Jewitt, University of Hawaii

48. IAU Official Position • IAU defines Pluto to be a planet • IAU cannot define “planet” • Upper limit: not massive enough to produce any form of fusion at its core • Deuterium fusion occurs for objects about 15 times Jupiter’s mass • No lower limit specified • Reasonable lower limit? • Massive enough for gravity to make it spherical • At least 13 planets • No reasonable definition produces 9 planets

49. What is a Planet? • Solar system alone is category of one • What about other solar systems?