Origin of the Structure of the Kuiper Belt During a Dynamical

Instability in the Orbits of Uranus and Neptune (“the Nice Model”)

Nathan Kaib5/16/08

Levison, H., Morbidelli, A., VanLaerhoven, C., Gomes, R., & Tsiganis, K.Icarus, Accepted

Outline

• Description of Kuiper Belt

• Giant Planet Migration and the Nice Model

• Simulation Results

• Conclusions

Outline

• Description of Kuiper Belt

• Giant Planet Migration and the Nice Model

• Simulation Results

• Conclusions

Properties of the Kuiper Belt

• Missing Mass: KB only contains 0.01 – 0.1 Earth masses

• Need 2-3 orders of magnitude more mass to accrete 100-1000 km bodies

Properties of the Kuiper Belt

• 10 – 50% of objects found in resonances with Neptune

• Inclinations extend up to ~40o

Properties of the Kuiper Belt

• Contains large population of excited orbits that do not pass near planets now

- Scattered Disk

Properties of the Kuiper Belt

• Contains double peaked inclination distribution:

-“Hot” population

-“Cold” populationHot

Cold

Properties of the Kuiper Belt

• Hot and Cold populations have different properties

Hot

Cold

Bluer, Larger

Redder, Smaller

Properties of the Kuiper Belt

• Cold, low e population has sharp cutoff at 1:2 resonance with Neptune

Outline

• Description of Kuiper Belt

• Giant Planet Migration and the Nice Model

• Simulation Results

• Conclusions

Planetesimal Scattering

Outer Planet Migration

• Nep, Ura, and Sat much more likely to scatter bodies in than eject them

• Jupiter’s energy kicks are powerful enough to eject most bodies

SU

J

N

Outer Planet Migration

Neptune, Uranus, and Saturn migrate outwards and Jupiter moves in to conserve angular momentum

Current Planet Configuration

1:2 MMR

Saturn currently is ~1.3 AU beyond the 1:2 MMR with Jupiter

The Nice Model

1:2 MMR ~35 AU

If there were 10’s of Earth masses of material beyond Neptune originally, then Saturn must have crossed the 1:2 MMR with Jupiter

• Saturn crossing 1:2 MMR causes orbits of U and N to become chaotic

• Dynamical friction due to scattering damps re-circurlarizes orbits

Nice Model Can Explain…

• Cataclysmic Late Heavy Bombardment 3.8 Gyrs ago

• High inclinations of Jovian Trojans• Existence of cometary bodies in main

asteroid belt• Significant non-zero inclinations and

eccentricities of giant planets• Irregular satellite populations of giant

planets

Nice Model Can Explain…

• Cataclysmic Late Heavy Bombardment 3.8 Gyrs ago

• High inclinations of Jovian Trojans• Existence of cometary bodies in main

asteroid belt• Significant non-zero inclinations and

eccentricities of giant planets• Irregular satellite populations of giant

planets

Nice Model Can Explain…

• Cataclysmic Late Heavy Bombardment 3.8 Gyrs ago

• High inclinations of Jovian Trojans• Existence of cometary bodies in main

asteroid belt• Significant non-zero inclinations and

eccentricities of giant planets• Irregular satellite populations of giant

planets

Nice Model Can Explain…

• Cataclysmic Late Heavy Bombardment 3.8 Gyrs ago

• High inclinations of Jovian Trojans• Existence of cometary bodies in main

asteroid belt• Significant non-zero inclinations and

eccentricities of giant planets• Irregular satellite populations of giant

planets

Nice Model Can Explain…

• Cataclysmic Late Heavy Bombardment 3.8 Gyrs ago

• High inclinations of Jovian Trojans• Existence of cometary bodies in main

asteroid belt• Significant non-zero inclinations and

eccentricities of giant planets• Irregular satellite populations of giant

planets

Outline

• Description of Kuiper Belt

• Giant Planet Migration and the Nice Model

• Simulation Results

• Conclusions

Simulations• Start planets at last

scattering between Uranus and Neptune

• Surround Neptune’s orbit with torus of 60,000 test particles extending to 34 AU

• Vary Neptune’s starting place and e-damping in sims

Simulations

Observed Simulated

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Observed Simulated

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Observed Simulated

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Hot

Cold

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Observed Simulated

Results SummaryKuiper Belt Mass: Simulations predict 0.05 to

0.14 Earth massesResonant Populations: Inclinations and

eccentricities reproduced well, Numbers?

Scattered Disk: Distribution of a and q reproduced

Bimodal Inclinations: Reproduced

Physical Differences in Hot and Cold Pops:

Cold and Hot bodies originate in different areas

1:2 Resonance Cold Boundary:

Cold pops. all stop near 1:2 MMR

Conclusions

• Nice Model reproduces more properties of Kuiper Belt than any other previous scenario

• Eccentricities of cold belt too high by a factor of 2

• May be due to unaccounted for physics such as collisional damping