Eccentric Extrasolar Planets: The Jumping Jupiter Model

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Eccentric Extrasolar Planets The Jumping Jupiter
Model

• Stacy Teng
• TERPS Conference
• Dec. 9, 2004

HD217107b as imagined by Lynette Cook
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Background

• Formation of Jupiter and Saturn in our Solar
  System
• Gradual accumulation of planetesimals into cores
  followed by gravitational capture of gaseous
  envelopes from the surrounding nebula
• Theory needs the giant planets to have formed
  beyond the snow line (at 4AU) so volatiles
  could condense into ices for capture
• Jupiter and Saturn formed on almost circular
  orbits as expected for protoplanets evolving from
  an accretion disk
• See the same thing in other planetary systems?
  No!

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Extrasolar Planets

• Jupiter-mass planets detected by Doppler shift
• Biased toward massive planets with short orbital
  periods
• Most of the planets detected have semimajor axis
  lt 4 AU
• What is the formation mechanism of these Hot
  Jupiters?

Diagram by Marcy et al., updated March, 2004
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Formation Theory

• Hot Jupiters formed near the stars Bodenheimer
  et al. (2000)
• Need to accrete a lot of mass quickly
• Migration tidal coupling Lin et al. (1996)
• Interaction between the planet and the disk to
  move the planet inward
• Does not explain the large eccentricities that
  are observed

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Formation Theory

• Migration Jumping Jupiter Model
• A system with 3 or more planets
• Encroachment of the Hill spheres as the planets
  grow
• Numerical simulations
• Systems with 3 planets each with 10-3 Msun
• Planets had various initial separations
• Non-coplanar planets with initial inclinations
  0.5, 1, and 1.5 degrees for the inner, middle,
  and outer planet
• Full tri-dimensional integrations using a mixed
  variable symplectic integrator with fixed
  stepsize of 20 days

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Simulation Results

• Result of the simulations
• 1 planet gets ejected from the system
• 1 planet moves to a smaller orbit
• 1 planet migrates further out
• Theory works even for systems with planets formed
  within 2 AU

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Comparison with Observations

• Statistical distribution of eccentricity agrees
  well with current data
• As the systems evolve, semimajor axis will get
  smaller as the orbits get circularized
• Future observations should detect distant planets
  in systems currently known to have planets

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References

• Marzari, F. Weidenschilling, S.J., 2002,
  Icarus, 156, 570
• Levison, H.F. Duncan, M.J., 1994, Icarus, 108,
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• http//www.obspm.fr/encycl/pictures.html