Anders Johansen
Professor
Vapor equilibrium models of accreting rocky planets demonstrate direct core growth by pebble accretion
Author
Summary, in English
The gaseous envelope of an accreting rocky planet becomes hot enough to sublimate silicates and other refractory minerals. For this work, we studied the effect of the resulting envelope enrichment with a heavy vapor species on the composition and temperature of the envelope. For simplification, we used the gas-phase molecule SiO to represent the sublimation of silicate material. We solved the equilibrium structure equations in 1D for planets in the mass range of 0.1 to 3 M⊙. The convective stability criterion was extended to take the stabilizing effect of the condensation of SiO clouds into account. We assumed that the envelope is both in hydrostatic equilibrium and in vapor equilibrium with the underlying magma ocean. This means that pebbles do not undergo sublimation in the envelope and therefore survive until they plunge into the magma ocean. We find that the emergence of an inner radiative region, where SiO condensation suppresses convection, increases the pressure and temperature in the inner envelope compared to pure H2/He envelopes once Mpl ≥ 0.3 M⊙. For Mpl > 0.75 M⊙, the temperature and pressure close to the surface reach the supercritical point of SiO. The amount of SiO stored in the envelope is lower than the total planet mass for low mass planets. However, for Mpl > 2.0 M⊙, all accreted pebble material must contribute to maintain the vapor equilibrium in the envelope. Therefore, the non-vapor mass of the planet ceases to increase beyond this threshold. Overall, our vapor equilibrium model of the planetary envelope allows for direct core growth by pebble accretion up to much higher masses than previously thought.
Department/s
- Astrophysics
Publishing year
2024
Language
English
Publication/Series
Astronomy and Astrophysics
Volume
683
Document type
Journal article
Publisher
EDP Sciences
Topic
- Astronomy, Astrophysics and Cosmology
Keywords
- Planets and satellites: atmospheres
- Planets and satellites: composition
- Planets and satellites: formation
- Planets and satellites: terrestrial planets
Status
Published
ISBN/ISSN/Other
- ISSN: 0004-6361