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GEOL 3045: Planetary Geology

GEOL 3045: Planetary Geology. Lysa Chizmadia Edgeworth-Kuiper Belt. Introduction. Discovered in 1992 by David Jewitt & Jane Luu Estimated >70,000 objects >100km Estimated mass: 0.06-0.3 x  Source for short-period comets Period < 200 years. HST image.

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GEOL 3045: Planetary Geology

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  1. GEOL 3045: Planetary Geology Lysa Chizmadia Edgeworth-Kuiper Belt

  2. Introduction • Discovered in 1992 by David Jewitt & Jane Luu • Estimated >70,000 objects >100km • Estimated mass: 0.06-0.3 x  • Source for short-period comets • Period < 200 years HST image Images from: http://www.nineplanets.org/kboc.html Image from:Malhotra & Williams (1997)

  3. Structure of the Kuiper Belt • EKB from 30-55 AU • Main body from 3:2 at 39.5Au to 1:2 at 48AU • Thick: up to 10 outside ecliptic • More diffuse distribution extends further Image from: http://en.wikipedia.org/wiki/Kuiper_belt

  4. Quaoar Sedna Kuiper Belt Objects • NH3, CH4 & H2O ices • Quaoar: • Xline H2O, not amorph • resurfaced Images from: http://en.wikipedia.org/wiki/Kuiper_belt

  5. Types of KBOs • Name is controversial • AKA Trans-Neptunian Objects (TNOs) • Includes KBOs but also all other objects orbiting Sun at the edge of the solar system • Three main groups: • Classical objects • Resonant objects • Scattered objects Images from: http://en.wikipedia.org/wiki/Kuiper_belt

  6. Classical Objects • AKA cubiwanos (Q-B-1-os) • 42-47 AU • No resonances w/ Neptune • Two populations: • Dynamically cold: • Nearly circular orbits (e<0.1) • Low inclinations <10 • Redder compositions • Formed + in position, may have migrated w/ Neptune • Dynamically hot: • Nearly circular orbits (e<0.1) • Higher inclinations <30 • Thought to have formed near Jupiter & the ejected Image from: Jewitt & Luu (1995)

  7. Resonant Objects • Locked in mean motion resonances with Neptune • 2:3 ~ Pluto “Plutinos” • Semi major axis ~ 39.4 AU • ~200 objects • 1:2 called “twotinos” • Semi major axis ~47.7 AU • Sparesely populated • Minor resonances: • 3:4, 3:5, 4:7, 2:5 • >50 AU “Kuiper Cliff” Image from: Jewitt et al. (1998) Image from: http://en.wikipedia.org/wiki/Kuiper_belt

  8. Scattered Objects • High eccentricities • 0.59 • High inclinations • ~24° • Origin of Jupiter-family comets Image from: Duncan & Levison (1997) Image from: http://en.wikipedia.org/wiki/Kuiper_belt

  9. Pluto System • Barycenter between Pluto & Charon • At least 3 moons • Charon (double object) • Nix (in same plane as Charon) • Hydra (~1:6 res w/ Charon) • Atmosphere: • N2, CH4, CO • Structure: (=1.8-2.1 g/cm3) • 1) Frozen N2 • 2) H2O ice • 3) Silicate & H2O ice Image from: http://en.wikipedia.org/wiki/Pluto_%28astronomy%29 Images from: http://en.wikipedia.org/wiki/Charon_(moon)

  10. Pro: Hydrostatic equilibrium (spherical shape) Primarily orbits Sun Larger than 1000 km Largest object in general vicinity (has cleared its neighborhood) Con: High inclination High eccentricity Orbits barycenter w/ Charon Not largest object in KB (has not cleared its neighborhood) Pluto As A Planet Images from: http://en.wikipedia.org/wiki/2006_definition_of_planet

  11. Centaur Comets • Orbit between Jupiter & Neptune • Orbits not stable • At least 3 display cometary comas • Probably from KB • Reflectance spectra: • Amorphous carbon • Hydrocarbons • Methanol ice Image from: Stern & Campins (1996)

  12. Formation Theories • The classical & resonant KBOs probably not primordial • Inclinations & eccentricities too high • Three formation theories: • Long-term effects of planetary perturbations • Resonant sweeping due to planetary migration • Massive scatterers resulting in impacts & gravitational perturbations • As of 2006, 9 other star systems have KB-like disks Images from: http://en.wikipedia.org/wiki/Kuiper_belt

  13. From 33-50 AU Composed of NH3, CH4 & H2O ices Quaoar has crystalline H2O ice on surface Evidence for resurfacing Three types of objects: Classical Resonant Scattered Centaur comets similar compositions Probably originated in KB Pluto’s status as a planet Hydrostatic equilibrium Primarily orbits sun Has cleaned up neighborhood? New Horizons Summary Image from: http://en.wikipedia.org/wiki/Kuiper_belt

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