GEOL 3045: Planetary GeologyGEOL 3045: Planetary Geology
Lysa ChizmadiaEdgeworth-Kuiper Belt
Lysa ChizmadiaEdgeworth-Kuiper Belt
IntroductionIntroduction 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
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
Images from: http://www.nineplanets.org/kboc.html
HST image
Image from:Malhotra & Williams (1997)
Structure of the Kuiper BeltStructure 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
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
Images from: http://en.wikipedia.org/wiki/Kuiper_belt
Quaoar
Sedna
Kuiper Belt ObjectsKuiper Belt Objects NH3, CH4 & H2O ices Quaoar:
– Xline H2O, not amorph
– resurfaced
NH3, CH4 & H2O ices Quaoar:
– Xline H2O, not amorph
– resurfaced
Types of KBOsTypes 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
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
Classical ObjectsClassical 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
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)
Image from: http://en.wikipedia.org/wiki/Kuiper_belt
Image from: Jewitt et al. (1998)
Resonant ObjectsResonant 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”
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”
Scattered ObjectsScattered Objects High eccentricities
– 0.59 High inclinations
– ~24° Origin of Jupiter-family
comets
High eccentricities– 0.59
High inclinations– ~24°
Origin of Jupiter-family comets
Image from: http://en.wikipedia.org/wiki/Kuiper_belt
Image from: Duncan & Levison (1997)
Pluto SystemPluto 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
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
Images from: http://en.wikipedia.org/wiki/Charon_(moon)
Image from: http://en.wikipedia.org/wiki/Pluto_%28astronomy%29
Pluto As A PlanetPluto As A Planet Pro:
– Hydrostatic equilibrium (spherical shape)
– Primarily orbits Sun– Larger than 1000 km– Largest object in
general vicinity (has cleared its neighborhood)
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)
Con:– High inclination– High eccentricity– Orbits barycenter w/
Charon– Not largest object in
KB (has not cleared its neighborhood)
Images from: http://en.wikipedia.org/wiki/2006_definition_of_planet
Centaur CometsCentaur Comets Orbit between Jupiter &
Neptune– Orbits not stable
At least 3 display cometary comas
Probably from KB Reflectance spectra:
– Amorphous carbon– Hydrocarbons– Methanol ice
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)
Formation TheoriesFormation 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
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
SummarySummary 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
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
Image from: http://en.wikipedia.org/wiki/Kuiper_belt
New Horizons
Pluto’s status as a planet– Hydrostatic
equilibrium– Primarily orbits sun– Has cleaned up
neighborhood?
Pluto’s status as a planet– Hydrostatic
equilibrium– Primarily orbits sun– Has cleaned up
neighborhood?