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Formation and composition of extrasolar

planetsA. Thiabaud - U. Marboeuf - Y. Alibert - N. Cabral

I. Leya - K. Mezger

LINZ - SEPT. 5, 2013

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IntroductionComposition of planets is linked to its structure. Knowing it can provide informations on :

• Equation of state • mean molecular weight• density

• Radius of the planet (see, eg. Swift et al. 2012)• Atmosphere• Better understanding of planet formation and evolution

Chemistry will also induce changes in the disc properties (temperature, pressure, and opacity especially)

WHAT COMPOSITION CAN TELL US

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Introduction

• Refractory : Tc>Tc

H2O

• Volatile : Tc<Tc

H2O

DEFINITIONS

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PlaneteTHE BERN PLANET FORMATION MODEL

• Initial planet formation model by Alibert et al. 2005 => Giant planets

• Improvements: • Population Synthesis (Mordasini et al.,2009 a,b)• Accretion rate of planetesimals (Fortier et al. 2013)• Formation of planetary systems (Alibert et al. 2013)

• Surface density:

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PlaneteMIGRATION OF PLANETS

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Assumptions• Composition of the solar nebula.

• Atoms in gaseous phase.

• Volatiles : CO2, CO, NH3, N2, H2O, CH4, CH3OH, H2S.

• Abundances of Lodders 2003.

• Non-irradiated disk.

• no chemical reactions.  

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Refractory elementsSOME THERMODYNAMICS

• Formation of refractory elements based on condensation sequence at equilibrium.

• Minimization of Gibbs energy :

• Computation of the condensation sequence for T(r), P(r) provided by the planet formation model.

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Volatile elementsCOOLING CURVES

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ResultsREFRACTORY ELEMENTS IN THE DISK

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ResultsVOLATILE SPECIES - ICE LINE

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ResultsREFRACTORY MASS FRACTION IN PLANETS

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ResultsMEAN COMPOSITION OF PLANETS

Rocky planets

Giant/icy planets

All numbers in wt%

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ResultsCHANGES WITH INITIAL SURFACE

DENSITY

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Conclusions

• Every planet of the Solar System can be chemically reproduced by our model. (Even Mercury !)

•Giant planets are depleted in volatile elements, compared to icy or Neptune/Saturne-like planets.

•A relation between the disc parameters and the position of the iceline was derived.

•The use of self-consistent models, with a population of discs, is needed to form a large diversity of planets.