The Deposition of Heavy Elements in Giant Protoplanetary Atmospheres: The Importance of Planetesimal–Envelope Interactions

Valletta, Claudio; Helled, Ravit

doi:10.3847/1538-4357/aaf427

Cited by 41 publications

(40 citation statements)

References 42 publications

(79 reference statements)

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“…In our previous work (Valletta & Helled 2019) (hereafter VH19) we performed a first step towards a self-consistent model for giant planet formation where we analyzed planetesimals' mass loss with pre-computed structure models of the planet at different times. We investigated how ablation and fragmentation depend on various parameters such as the planetesimal's size and composition, different ablation efficiencies (C h factor) as well as the impact of assuming different fragmentation models.…”

Section: )mentioning

confidence: 99%

Jupiter’s heavy-element enrichment expected from formation models

Venturini

Helled

2020

A&A

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Aims. The goal of this work is to investigate Jupiter's growth focusing on the amount of heavy elements accreted by the planet, and its comparison 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 characterized 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 disk. The second and third phases are 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 (M P -M Z ) relation of M Z ∼ M 2/5 P when a gap in the planetesimal disk is created, and of M Z ∼ M 1/6 P 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 disk's dispersal.

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confidence: 99%

Jupiter’s heavy-element enrichment expected from formation models

Venturini

Helled

2020

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“…If a large solid object impacts it might encounter different fates. It might either just cross the atmosphere and pass the core, be captured by the atmosphere, reach the core and impact or be dismantled one way or the other during his passage of the atmosphere (Brouwers et al 2018;Valletta & Helled 2019). However, erosion of pebble pile planetesimals might be another option under certain conditions, especially compared to ablation which might only occur at friction far beyond the threshold shear stress for erosion.…”

Section: Interaction Of Planetesimals With Atmospheres Of Forming Giamentioning

confidence: 99%

Planetesimals in rarefied gas: wind erosion in slip flow

Demirci

Schneider

Steinpilz

et al. 2020

Monthly Notices of the Royal Astronomical Society

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A planetesimal moves through the gas of its protoplanetary disc where it experiences a head wind. Though the ambient pressure is low, this wind can erode and ultimately destroy the planetesimal if the flow is strong enough. For the first time, we observe wind erosion in ground based and microgravity experiments at pressures relevant in protoplanetary discs, i.e. down to 10 −1 mbar. We find that the required shear stress for erosion depends on the Knudsen number related to the grains at the surface. The critical shear stress to initiate erosion increases as particles become comparable to or larger than the mean free path of the gas molecules. This makes pebble pile planetesimals more stable at lower pressure. However, it does not save them as the experiments also show that the critical shear stress to initiate erosion is very low for sub-millimetre sized grains.

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“…Here, we make a brief discussion on such an effect. The interaction between planetesimals and protoplanet's atmosphere before the onset of runaway gas accretion is well studied (e.g., Podolak et al 1988;Inaba & Ikoma 2003;Valletta & Helled 2019). According to these studies, the gas drag from the atmosphere enhances the capture probability greatly.…”

Section: Effective Capture Radius Of the Growing Protoplanetmentioning

confidence: 99%

Capture of solids by growing proto-gas giants: effects of gap formation and supply limited growth

Shibata

Ikoma

2019

Monthly Notices of the Royal Astronomical Society

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Studies of internal structure of gas giant planets suggest that their envelopes are enriched with heavier elements than hydrogen and helium relative to their central stars. Such enrichment likely occurred by solid accretion during late formation stages of gas giant planets in which gas accretion dominates protoplanetary growth. Some previous studies performed orbital integration of planetesimals around a growing protoplanet with the assumption of an uniform circumstellar disc to investigate how efficiently the protoplanet captures planetesimals. However, not only planetesimals but also disc gas are gravitationally perturbed by the protoplanet in its late formation stages, resulting in gap opening in the circumstellar disc. In this study, we investigate the effects of such gap formation on the capture of planetesimals by performing dynamical simulations of planetesimals around a growing proto-gas giant planet. Gap formation reduces the surface density of disc gas, makes a steep pressure gradient and limits the growth rate of the protoplanet. We find that the first effect enhances the capture of planetesimals, while the others reduce it. Consequently the amount of planetesimals captured during the gas accretion is estimated to be at most ∼ 3 M ⊕ . We conclude that the in-situ capture of planetesimals needs the initial solid surface density more than five times higher than that of the minimum mass solar nebula for explaining the inferred large amount of heavy element in Jupiter. For highly dense warm Jupiters, we would need additional processes enhancing the capture and/or supply of planetesimals.

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The Deposition of Heavy Elements in Giant Protoplanetary Atmospheres: The Importance of Planetesimal–Envelope Interactions

Cited by 41 publications

References 42 publications

Jupiter’s heavy-element enrichment expected from formation models

Jupiter’s heavy-element enrichment expected from formation models

Planetesimals in rarefied gas: wind erosion in slip flow

Capture of solids by growing proto-gas giants: effects of gap formation and supply limited growth

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