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Formation and composition of extrasolar planets

This article discusses the formation and composition of extrasolar planets, delving into how a planet's composition reveals crucial insights about its structure, density, radius, and atmospheric characteristics. Initiatives such as the Bern Planet Formation Model and other updates from prominent researchers outline the complexities of planetary formation, including migration, the role of volatiles and refractories, and the thermodynamics involved in these processes. The findings indicate that the physical characteristics of a planet can be linked to disc properties, suggesting a deeper understanding of planetary systems' evolution is attainable through chemical modeling.

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Formation and composition of extrasolar planets

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  1. Formation and composition of extrasolar planets LINZ - SEPT. 5, 2013 • A. Thiabaud - U. Marboeuf - Y. Alibert - N. Cabral • I. Leya - K. Mezger

  2. Introduction WHAT COMPOSITION CAN TELL US • Composition 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) 2

  3. Introduction DEFINITIONS • Refractory : Tc>TcH2O • Volatile : Tc<TcH2O

  4. Planete THE 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:

  5. Planete MIGRATION OF PLANETS 5

  6. 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.  

  7. Refractory elements SOME 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.

  8. Volatile elements COOLING CURVES

  9. Results REFRACTORY ELEMENTS IN THE DISK

  10. Results VOLATILE SPECIES - ICE LINE

  11. Results REFRACTORY MASS FRACTION IN PLANETS

  12. Results MEAN COMPOSITION OF PLANETS Rocky planets Giant/icy planets All numbers in wt%

  13. Results CHANGES WITH INITIAL SURFACE DENSITY

  14. 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 ofplanets.

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