Threshold Radii of Volatile-rich Planets

Lozovsky, Michael; Helled, Ravit; Dorn, Caroline; Venturini, Julia

doi:10.3847/1538-4357/aadd09

Cited by 48 publications

(57 citation statements)

References 35 publications

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“…With the mass-radius relation in Chen & Kipping (2016), we set the lower value for the radius bin to 5 R ⊕ , as it is within 1σ of the best-fit relation for 30 M ⊕ , while the upper value is set to 20 R ⊕ . Using a sample of planets with known masses and radii, Lozovsky et al (2018) have recently shown that planets with radii >4 R ⊕ must have a significant H-He atmosphere (more than 10% of the planetary mass). Hence, our choice of 5 R ⊕ as the lower radius ensures that we include gaseous planets in our analysis.…”

Section: Comparison With Kepler Occurrence Ratementioning

confidence: 99%

Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate

Fernandes

Mulders

Pascucci

et al. 2019

ApJ

251

262

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The orbital distribution of giant planets is crucial for understanding how terrestrial planets form and predicting yields of exoplanet surveys. Here, we derive giant planets occurrence rates as a function of orbital period by taking into account the detection efficiency of the Kepler and radial velocity (RV) surveys. The giant planet occurrence rates for Kepler and RV show the same rising trend with increasing distance from the star. We identify a break in the RV giant planet distribution between ∼2-3 au -close to the location of the snow line in the Solar System -after which the occurrence rate decreases with distance from the star. Extrapolating a broken power-law distribution to larger semi-major axes, we find good agreement with the ∼ 1% planet occurrence rates from direct imaging surveys. Assuming a symmetric power law, we also estimate that the occurrence of giant planets between 0.1−100 au is 26.6 +7.5 −5.4 % for planets with masses 0.1-20 M J and decreases to 6.2 +1.5 −1.2 % for planets more massive than Jupiter. This implies that only a fraction of the structures detected in disks around young stars can be attributed to giant planets. Various planet population synthesis models show good agreement with the observed distribution, and we show how a quantitative comparison between model and data can be used to constrain planet formation and migration mechanisms.

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Section: Comparison With Kepler Occurrence Ratementioning

confidence: 99%

Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate

Fernandes

Mulders

Pascucci

et al. 2019

ApJ

251

262

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“…However, for the case of TOI-849b, the difference is expected to be very moderate since the planet mass is clearly dominated by heavy-elements. Lozovsky et al (2018) calculated the effect of varying atmospheric water content on planetary radii for fixed masses and H-He gas mass fractions. Applying their model to TOI-849b showed that the inferred planet radius is only affected on the few percent level for atmospheric water content ranging from 0 to 70%.…”

Section: Interior Structure Characterisationmentioning

confidence: 99%

A remnant planetary core in the hot-Neptune desert

Armstrong

Lopez

Adibekyan

et al. 2020

Nature

100

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The interiors of giant planets remain poorly understood. Even for the planets in the Solar System, difficulties in observation lead to major uncertainties in the properties of planetary cores. Exoplanets that have undergone rare evolutionary pathways provide a new route to understanding planetary interiors. We present the discovery of TOI-849b, the remnant core of a giant planet, with a radius smaller than Neptune but an anomalously high mass M p =40.8 +2.4 −2.5 M ⊕ and density of 5.5 ± 0.8 gcm −3 , similar to the Earth. Interior structure models suggest that any gaseous envelope of pure hydrogen and helium consists of no more than 3.9 +0.8 −0.9 % of the total mass of the planet. TOI-849b transits a late G type star (T mag = 11.5) with an orbital period of 18.4 hours, leading to an equilibrium temperature of 1800K. The planet's mass is larger than the theoretical threshold mass for runaway gas accretion. As such, the planet could have been a gas giant before undergoing extreme mass loss via thermal self-disruption or giant planet collisions, or it avoided substantial gas accretion, perhaps through gap opening or late formation. Photoevaporation rates cannot provide the mass loss required to reduce a Jupiter-like gas giant, but can remove a few M ⊕ hydrogen and helium envelope on timescales of several Gyr, implying that any remaining atmosphere is likely to be enriched by water or other volatiles from the planetary interior. TOI-849b represents a unique case where material from the primordial core is left over from formation and available to study.

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“…Some studies suggest that they had their atmospheres stripped by photo-evaporation (e.g., Lopez & Fortney 2013;Owen & Wu 2017;Jin & Mordasini 2018) or through the release of heat from their cores (Ginzburg et al 2018;Gupta & Schlichting 2019). The majority of close-in, intermediate-mass planets are substantially more voluminous, however, and must contain envelopes that carry at least a few percent of their mass (Lopez et al 2012;Lopez & Fortney 2014;Marcy et al 2014;Rogers 2015;Lozovsky et al 2018), in many instances more than can be produced just by outgassing (Rogers & Seager 2010). These planets are typically referred to as Sub-or Mini-Neptunes.…”

Section: Introductionmentioning

confidence: 99%

How planets grow by pebble accretion

Brouwers

Ormel

2020

A&A

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Context. Proto-planets embedded in their natal disks acquire hot envelopes as they grow and accrete solids. This ensures that the material they accrete – pebbles, as well as (small) planetesimals – will vaporize to enrich their atmospheres. Enrichment modifies an envelope’s structure and significantly alters its further evolution. Aims. Our aim is to describe the formation of planets with polluted envelopes from the moment that impactors begin to sublimate to beyond the disk’s eventual dissipation. Methods. We constructed an analytical interior structure model, characterized by a hot and uniformly mixed high-Z vapor layer surrounding the core, located below the usual unpolluted radiative-convective regions. Our model assumes an ideal equation of state and focuses on identifying trends rather than precise calculations. The expressions we derived are applicable to all single-species pollutants, but we used SiO2 to visualize our results. Results. The evolution of planets with uniformly mixed polluted envelopes follows four potential phases. Initially, the central core grows directly through impacts and rainout until the envelope becomes hot enough to vaporize and absorb all incoming solids. We find that a planet reaches runaway accretion when the sum of its core and vapor mass exceeds a value that we refer to as the critical metal mass – a criterion that supersedes the traditional critical core mass. The critical metal mass scales positively with both the pollutant’s evaporation temperature and with the planet’s core mass. Hence, planets at shorter orbital separations require the accretion of more solids to reach runaway as they accrete less volatile materials. If the solids accretion rate dries up, we identify the decline of the mean molecular weight – dilution – as a mechanism to limit gas accretion during a polluted planet’s embedded cooling phase. When the disk ultimately dissipates, the envelope’s inner temperature declines and its vapor eventually rains out, augmenting the mass of the core. The energy release that accompanies this does not result in significant mass-loss, as it only occurs after the planet has substantially contracted.

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Threshold Radii of Volatile-rich Planets

Cited by 48 publications

References 35 publications

Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate

Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate

A remnant planetary core in the hot-Neptune desert

How planets grow by pebble accretion

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