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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

Outline

Jupiter’s core mass and mass of heavyelements:

Interiors of Giant Planets

Saumon &Guillot (2004)

For MZ -the heavyelements aremixed in theH/He envelope

Saturn’s core mass and mass of heavyelements:

Interiors of Giant Planets

Saumon &Guillot (2004)

Its current luminosity is ~50% greater than predictedby models thatwork for Jupiter:

A Problem with Saturn ?...

Fortney & Hubbard (2004)

Saturn reaches its currentTeff (luminosity) in only2 Gyr !

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

A Problem with Saturn ?…

Phase diagram for H & He:

A Problem with Saturn ?...Fortney & Hubbard (2004)

Model results:

Stevenson (‘75)vs.Pfaffenzelleret al. (‘95) -

different signfor dA/dP !

New models:

A Problem with Saturn ?...Fortney & Hubbard (2004)

Model results:

The modified Pfaffenzelleret al. (‘95) phase diagramresolves the discrepancy.

Good match to observedhelium depletions in theatmospheres of Jupiter (Y=0.234) & Saturn (Y~0.2).

Cooling curves:

Evolution Models of Exo-planets:Fortney & Hubbard (2004)

Models:

All planets have 10 ME

cores & no irradiation.

The models with Heseparation have ~2 xhigher luminosities.

Could the very low-density “puffy” planetsbe heated by phase separation ?

Evolution Models of Exo-planets:

Phase separationof other elements

Ne, O

Could the very low-density “puffy” planetsbe heated by phase separation ?

Evolution Models of Exo-planets:

Phase separationof other elements

Ne, O

Ice Giants: Uranus & Neptune

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)