Volume 634, February 2020
|Number of page(s)||18|
|Section||Planets and planetary systems|
|Published online||03 February 2020|
Jupiter’s heavy-element enrichment expected from formation models
International Space Science Institute,
2 Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
Accepted: 27 November 2019
Aims. The goal of this work is to investigate Jupiter’s growth by focusing on the amount of heavy elements accreted by the planet, and to compare this with recent structure models of Jupiter.
Methods. Our model assumes an initial core growth dominated by pebble accretion, and a second growth phase that is characterised by a moderate accretion of both planetesimals and gas. The third phase is dominated by runaway gas accretion during which the planet becomes detached from the disc. The second and third phases were computed in detail, considering two different prescriptions for the planetesimal accretion and fits from hydrodynamical studies to compute the gas accretion in the detached phase.
Results. In order for Jupiter to consist of ~20–40 M⊕ of heavy elements as suggested by structure models, we find that Jupiter’s formation location is preferably at an orbital distance of 1 ≲ a ≲ 10 au once the accretion of planetesimals dominates. We find that Jupiter could accrete between ~1 and ~15 M⊕ of heavy elements during runaway gas accretion, depending on the assumed initial surface density of planetesimals and the prescription used to estimate the heavy-element accretion during the final stage of the planetary formation. This would yield an envelope metallicity of ~0.5 to ~3 times solar. By computing the solid (heavy-element) accretion during the detached phase, we infer a planetary mass-metallicity (MP–MZ) relation of MZ ~ MP2/5, when a gap in the planetesimal disc is created, and of MZ ~ MP1/6 without a planetesimal gap.
Conclusions. Our hybrid pebble-planetesimal model can account for Jupiter’s bulk and atmospheric enrichment. The high bulk metallicity inferred for many giant exoplanets is difficult to explain from standard formation models. This might suggest a migration history for such highly enriched giant exoplanets and/or giant impacts after the disc’s dispersal.
Key words: planets and satellites: gaseous planets / planets and satellites: composition / planets and satellites: formation
© ESO 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.