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Exploring Gas Giant Planets: Challenges in Model Alignment

This study delves into discrepancies in gas giant planet models, including issues with Jupiter's core, Saturn's luminosity, and helium phase separation. The research covers our solar system, ice giant planets, and evolution models for exoplanets, offering insights on mass distribution and phase diagrams for helium and hydrogen. The analysis also addresses the potential impact of phase separation on planetary evolution and surface characteristics.

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Exploring Gas Giant Planets: Challenges in Model Alignment

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  1. Gas Giant Planets. III. Some of the Hot Jupiters do not match well models based on Jupiter & Saturn: Gaudi (2005) & Charbonneau et al (2006) w Bodenheimer et al.(2003), Laughlin et al. (2005) models; and Burrows et al. (2003)

  2. Outline • Our own Solar System: Jupiter & Saturn • Eroding Jupiter’s core by convection ? • The problem with Saturn’s luminosity • Helium phase separation • Evolution models for extrasolar planets • Helium phase separation as a function of planetary mass • Ice Giant Planets: Uranus & Neptune

  3. Interiors of Giant Planets Jupiter’s core mass and mass of heavy elements: For MZ - the heavy elements are mixed in the H/He envelope Saumon & Guillot (2004)

  4. Interiors of Giant Planets Saturn’s core mass and mass of heavy elements: Saumon & Guillot (2004)

  5. A Problem with Saturn ?... Its current luminosity is ~50% greater than predicted by models that work for Jupiter: Saturn reaches its current Teff (luminosity) in only 2 Gyr ! Fortney & Hubbard (2004)

  6. A Problem with Saturn ?… • The only promising idea for resolving the discrepancy - phase separation of neutral He from liquid metallic H(Stevenson & Salpeter 1977): for a saturation number fraction of the solute (He), phase separation will occur when the temperature drops below T : x = exp (B - A/kT) where x=0.085 (solar comp., Y=0.27), B=const.(~0), A~1-2 eV (pressure- dependent const.), therefore T = 5,000 - 10,000 K

  7. A Problem with Saturn ?... Phase diagram for H & He: Fortney & Hubbard (2004) Model results: Stevenson (‘75) vs. Pfaffenzeller et al. (‘95) - different sign for dA/dP !

  8. A Problem with Saturn ?... New models: Fortney & Hubbard (2004) Model results: The modified Pfaffenzeller et al. (‘95) phase diagram resolves the discrepancy. Good match to observed helium depletions in the atmospheres of Jupiter (Y=0.234) & Saturn (Y~0.2).

  9. Evolution Models of Exo-planets: Cooling curves: Fortney & Hubbard (2004) Models: All planets have 10 ME cores & no irradiation. The models with He separation have ~2 x higher luminosities.

  10. Evolution Models of Exo-planets: Could the very low-density “puffy” planets be heated by phase separation ? Phase separation of other elements Ne, O

  11. Evolution Models of Exo-planets: Could the very low-density “puffy” planets be heated by phase separation ? Phase separation of other elements Ne, O

  12. Ice Giants: Uranus & Neptune

  13. Conclusions Sizes of extrasolar planets are already precise beware of biases & systematic errors Models are based on Jupiter & Saturn Perhaps, Hot & Very Hot Jupiters are more Z enriched: because of history - excessive migration through disk, or because of orbit - manage to capture more planetesimals ? Implications for the core-accretion model: it requires at least ~6 ME for Mcore of Jupiter & Saturn invoke Jupiter core erosion (e.g. Guillot 2005), use the He settling for Saturn (Fortney & Hubbard 2003)

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