Where Are the Water Worlds? Identifying Exo-water-worlds Using Models of Planet Formation and Atmospheric Evolution

Chakrabarty, Aritra; Mulders, Gijs D.

doi:10.3847/1538-4357/ad3802

Cited by 6 publications

(2 citation statements)

References 76 publications

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“…These models make the assumption that sub-Neptunes form in situ with an Earth-like rocky core and H/He primordial envelope. Theory predicts a large fraction of water-rich cores interior to 1 au (Aguichine et al 2021;Chakrabarty & Mulders 2024;Burn et al 2024), which could impact the evolved sub-Neptune population.…”

Section: Possible Hypotheses To Explain the Measured Cliff Shapementioning

confidence: 99%

A Unified Treatment of Kepler Occurrence to Trace Planet Evolution. II. The Radius Cliff Formed by Atmospheric Escape

Dattilo,

Batalha

2024

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The Kepler mission enabled us to look at the intrinsic population of exoplanets within our galaxy. In period-radius space, the distribution of the intrinsic population of planets contains structure that can trace planet formation and evolution history. The most distinctive feature in period-radius space is the radius cliff, a steep drop-off in occurrence between 2.5 and 4R ⊕ across all period ranges, separating the sub-Neptune population from the rarer Neptunes orbiting within 1 au. Following our earlier work to measure the occurrence rate of the Kepler population, we characterize the shape of the radius cliff as a function of orbital period (10–300 days) as well as insolation flux (9500S ⊕–10S ⊕). The shape of the cliff flattens at longer orbital periods, tracking the rising population of Neptune-sized planets. In insolation, however, the radius cliff is both less dramatic and the slope is more uniform. The difference in this feature between period space and insolation space can be linked to the effect of EUV/X-ray versus bolometric flux in the planet’s evolution. Models of atmospheric mass loss processes that predict the location and shape of the radius valley also predict the radius cliff. We compare our measured occurrence rate distribution to population synthesis models of photoevaporation and core-powered mass loss in order to constrain formation and evolution pathways. We find that the models do not statistically agree with our occurrence distributions of the radius cliff in period space or insolation space. Atmospheric mass loss that shapes the radius valley cannot fully explain the shape of the radius cliff.

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Section: Possible Hypotheses To Explain the Measured Cliff Shapementioning

confidence: 99%

A Unified Treatment of Kepler Occurrence to Trace Planet Evolution. II. The Radius Cliff Formed by Atmospheric Escape

Dattilo,

Batalha

2024

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“…In this scenario, the ice/rock nucleus would accrete some amount of H/He, which would subsequently mix with the H 2 O layer to form an extended H/He/H 2 O envelope, with H 2 O in vapor and/or supercritical phases. A commonly assumed composition for water worlds is a 1:1 ratio of iron and rock to H 2 O (e.g., Zeng et al 2019;Luque & Pallé 2022;Chakrabarty & Mulders 2024). This ratio is ultimately derived from the estimated solar system ice-to-rock ratio of 1.17:1 reported in Lodders (2003).…”

Section: Implications For Planet Formationmentioning

confidence: 99%

New Insights into the Internal Structure of GJ 1214 b Informed by JWST

Nixon,

Piette,

Kempton

et al. 2024

ApJL

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Recent JWST observations of the sub-Neptune GJ 1214 b suggest that it hosts a high-metallicity (≳100× solar), hazy atmosphere. Emission spectra of the planet show molecular absorption features, most likely due to atmospheric H2O. In light of this new information, we conduct a thorough reevaluation of the planet’s internal structure. We consider interior models with mixed H/He/H2O envelopes of varying composition, informed by atmospheric constraints from the JWST phase curve, in order to determine possible bulk compositions and internal structures. Self-consistent atmospheric models consistent with the JWST observations are used to set boundary conditions for the interior. We find that a total envelope mass fraction of at least 8.1% is required to explain the planet’s mass and radius. Regardless of H2O content, the maximum H/He mass fraction of the planet is 5.8%. We find that a 1:1 ice-to-rock ratio along with 3.4%–4.8% H/He is also a permissible solution. In addition, we consider a pure H2O (steam) envelope and find that such a scenario is possible, albeit with a high ice-to-rock ratio of at least 3.76:1, which may be unrealistic from a planet formation standpoint. We discuss possible formation pathways for the different internal structures that are consistent with observations. Since our results depend strongly on the atmospheric composition and haze properties, more precise observations of the planet’s atmosphere would allow for further constraints on its internal structure. This type of analysis can be applied to any sub-Neptune with atmospheric constraints to better understand its interior.

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Suppression of giant planet formation around low-mass stars in clustered environments

Huang,

Portegies Zwart,

Wilhelm

2024

A&A

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Current exoplanet formation studies tend to overlook the birth environment of stars in clustered environments. However, the effects of this environment on the planet formation process are important, especially in the earliest stage. We investigate the differences in planet populations forming in star-cluster environments through pebble accretion and compare these results with planet formation around isolated stars. We strive to provide potential signatures of the young planetary systems to guide future observations. We present a new planet population synthesis code designed for clustered environments. This planet formation model is based on pebble accretion and includes migration in the circumstellar disk. The disk's gas and dust have been evolved via 1D simulations, while considering the effects of photo-evaporation of the nearby stars. Planetary systems in a clustered environment are different than those born in isolation; the environmental effects are important for a wide range of observable parameters and the eventual architecture of the planetary systems. Planetary systems born in a clustered environment lack cold Jupiters, as compared to isolated planetary systems. This effect is more pronounced for low-mass stars (lesssim 0.2 $M_ On the other hand, planetary systems born in clusters show an excess of cold Neptune around these low-mass stars. In future observations, finding an excess of cold Neptunes and a lack of cold Jupiters could be used to constrain the birth environments of these planetary systems. Exploring the dependence of cold Jupiter's intrinsic occurrence rate on stellar mass offers insights into the birth environment of their proto-embryos.

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Where Are the Water Worlds? Identifying Exo-water-worlds Using Models of Planet Formation and Atmospheric Evolution

Cited by 6 publications

References 76 publications

A Unified Treatment of Kepler Occurrence to Trace Planet Evolution. II. The Radius Cliff Formed by Atmospheric Escape

A Unified Treatment of Kepler Occurrence to Trace Planet Evolution. II. The Radius Cliff Formed by Atmospheric Escape

New Insights into the Internal Structure of GJ 1214 b Informed by JWST

Suppression of giant planet formation around low-mass stars in clustered environments

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