Unified Simulations of Planetary Formation and Atmospheric Evolution: Effects of Pebble Accretion, Giant Impacts, and Stellar Irradiation on Super-Earth Formation

Ogihara, Masahiro; Hori, Yasunori

doi:10.3847/1538-4357/ab7fa7

Cited by 28 publications

(33 citation statements)

References 96 publications

(154 reference statements)

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“…Giant collisions, which may be important at the time of disc dispersal (Ogihara & Hori 2020), are, in addition to photoevaporation, a possible mechanism that could help in removing a planet's atmosphere. Although we did not consider collisions in our simulations since we formed only one planet per simulation, we can estimate in a simple way the fraction of envelope mass-loss a planet could undergo if we allowed it to collide with another lessmassive planet, formed isolated in the same disc.…”

Section: Appendix D: Envelope Mass-loss By Giant Impactsmentioning

confidence: 99%

“…For simplicity and following the results of Ogihara & Hori (2020), who report only one or two giant impacts when accounting for N-body interactions, we allow only one collision per planet, but compute all the possible results of that collision considering that all the less-massive planets in the same disc (with final periods <100 days), can be the impactor. We compute mean values for the core mass, envelope mass, and core ice fraction for each 'family of impacts'.…”

Section: Appendix D: Envelope Mass-loss By Giant Impactsmentioning

confidence: 99%

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The nature of the radius valley

Venturini

Guilera

Haldemann

et al. 2020

A&A

151

117

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The existence of a radius valley in the Kepler size distribution stands as one of the most important observational constraints to understand the origin and composition of exoplanets with radii between those of Earth and Neptune. In this work we provide insights into the existence of the radius valley, first from a pure formation point of view and then from a combined formation-evolution model. We run global planet formation simulations including the evolution of dust by coagulation, drift, and fragmentation, and the evolution of the gaseous disc by viscous accretion and photoevaporation. A planet grows from a moon-mass embryo by either silicate or icy pebble accretion, depending on its position with respect to the water ice line. We include gas accretion, type I–II migration, and photoevaporation driven mass-loss after formation. We perform an extensive parameter study evaluating a wide range of disc properties and initial locations of the embryo. We find that due to the change in dust properties at the water ice line, rocky cores form typically with ∼3 M⊕ and have a maximum mass of ∼5 M⊕, while icy cores peak at ∼10 M⊕, with masses lower than 5 M⊕ being scarce. When neglecting the gaseous envelope, the formed rocky and icy cores account naturally for the two peaks of the Kepler size distribution. The presence of massive envelopes yields planets more massive than ∼10 M⊕ with radii above 4 R⊕. While the first peak of the Kepler size distribution is undoubtedly populated by bare rocky cores, as shown extensively in the past, the second peak can host half-rock–half-water planets with thin or non-existent H-He atmospheres, as suggested by a few previous studies. Some additional mechanisms inhibiting gas accretion or promoting envelope mass-loss should operate at short orbital periods to explain the presence of ∼10–40 M⊕ planets falling in the second peak of the size distribution.

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Section: Appendix D: Envelope Mass-loss By Giant Impactsmentioning

confidence: 99%

Section: Appendix D: Envelope Mass-loss By Giant Impactsmentioning

confidence: 99%

The nature of the radius valley

Venturini

Guilera

Haldemann

et al. 2020

A&A

151

117

View full text Add to dashboard Cite

show abstract

“…Despite the basic success of the core-accretion model in explaining that low-mass planets can acquire a H/He envelope, it has failed to quantitatively explain the properties of observed sub-Neptunes (e.g. Lee et al 2014;Ogihara & Hori 2020;Alessi et al 2020). In fact the issue is not that they have accreted H/He atmospheres, it is that they have only accreted a few percent by mass, even after massloss processes like photoevaporation (Jankovic et al 2019;Ogihara & Hori 2020) and/or core-powered mass-loss (e.g.…”

Section: Introductionmentioning

confidence: 99%

Constraining the entropy of formation from young transiting planet

Owen

2020

Monthly Notices of the Royal Astronomical Society

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Recently K2 and TESS have discovered transiting planets with radii between ∼ 5-10 R⊕ around stars with ages <100 Myr. These young planets are likely to be the progenitors of the ubiquitous super-earths/sub-neptunes, that are well studied around stars with ages ≳ 1 Gyr. The formation and early evolution of super-earths/sub-neptunes are poorly understood. Various planetary origin scenarios predict a wide range of possible formation entropies. We show how the formation entropies of young (∼20-60 Myr), highly irradiated planets can be constrained if their mass, radius and age are measured. This method works by determining how low-mass a H/He envelope a planet can retain against mass-loss. This lower bound on the H/He envelope mass can then be converted into an upper bound on the entropy. If planet mass measurements with errors ≲ 20% can be achieved for the discovered young planets around DS Tuc A and V1298 Tau, then insights into their origins can be obtained. For these planets, higher measured planet masses would be consistent with standard core-accretion theory. In contrast, lower planet masses (≲ 6 − 7 M⊕) would require a “boil-off” phase during protoplanetary disc dispersal to explain.

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“…Owen and Wu 2017;Kubyshkina et al 2019a;Rogers and Owen 2020). However, the quantitative details are still uncertain, with most planet formation models over-predicting the amount of H/He a planet can accrete (Jankovic et al 2019;Ogihara and Hori 2020).…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Dominated Atmospheres on Terrestrial Mass Planets: Evidence, Origin and Evolution

et al. 2020

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The discovery of thousands of highly irradiated, low-mass, exoplanets has led to the idea that atmospheric escape is an important process that can drive their evolution. Of particular interest is the inference from recent exoplanet detections that there is a large population of low mass planets possessing significant, hydrogen dominated atmospheres, even at masses as low as $\sim 2~\mbox{M}_{\oplus }$ ∼ 2 M ⊕ . The size of these hydrogen dominated atmospheres indicates the envelopes must have been accreted from the natal protoplanetary disc. This inference is in contradiction with the Solar System terrestrial planets, that did not reach their final masses before disc dispersal, and only accreted thin hydrogen dominated atmospheres. In this review, we discuss the evidence for hydrogen dominated atmospheres on terrestrial mass ($\lesssim 2~\mbox{M}_{\oplus }$ ≲ 2 M ⊕ ) planets. We then discuss the possible origins and evolution of these atmospheres with a focus on the role played by hydrodynamic atmospheric escape driven by the stellar high-energy emission (X-ray and EUV; XUV).

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Unified Simulations of Planetary Formation and Atmospheric Evolution: Effects of Pebble Accretion, Giant Impacts, and Stellar Irradiation on Super-Earth Formation

Cited by 28 publications

References 96 publications

The nature of the radius valley

The nature of the radius valley

Constraining the entropy of formation from young transiting planet

Hydrogen Dominated Atmospheres on Terrestrial Mass Planets: Evidence, Origin and Evolution

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