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?