Possible In Situ Formation of Uranus and Neptune via Pebble Accretion

Valletta, Claudio; Helled, Ravit

doi:10.3847/1538-4357/ac5f52

Cited by 9 publications

(7 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Never the less, recent results for Jupiter using data from the Juno mission (Wahl et al 2017 ;Nettelmann et al 2021 ;Miguel et al 2022 ) and on Saturn using ring seismology (Mankovich & Fuller 2021 ), E-mail: bloot@astron.nl show that giant planet interiors are more complex than previously thought. All these models show inhomogeneous envelopes with a distribution of metals that gradually decreases from the core to the most external layer, a result that is also supported by the most recent formation models of giant planets (Lozo vsk y et al 2018 ;Valletta & Helled 2022 ).…”

supporting

confidence: 72%

Exoplanet interior retrievals: core masses and metallicities from atmospheric abundances

Bloot

Miguel

Bazot

et al. 2023

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The mass and distribution of metals in the interiors of exoplanets are essential for constraining their formation and evolution processes. Nevertheless, with only masses and radii measured, the determination of exoplanet interior structures is degenerate, and so far simplified assumptions have mostly been used to derive planetary metallicities. In this work, we present a method based on a state-of-the-art interior code, recently used for Jupiter, and a Bayesian framework, to explore the possibility of retrieving the interior structure of exoplanets. We use masses, radii, equilibrium temperatures, and measured atmospheric metallicities to retrieve planetary bulk metallicities and core masses. Following results on the giant planets in the solar system and recent development in planet formation, we implement two interior structure models: one with a homogeneous envelope and one with an inhomogeneous one. Our method is first evaluated using a test planet and then applied to a sample of 37 giant exoplanets with observed atmospheric metallicities from the pre-JWST era. Although neither internal structure model is preferred with the current data, it is possible to obtain information on the interior properties of the planets, such as the core mass, through atmospheric measurements in both cases. We present updated metal mass fractions, in agreement with recent results on giant planets in the solar system.

show abstract

supporting

confidence: 72%

Exoplanet interior retrievals: core masses and metallicities from atmospheric abundances

Bloot

Miguel

Bazot

et al. 2023

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…The planets have very different mean densities, which displays the different outcomes of planetary formation and evolution within one system. The diversity of intermediate-mass exoplanets seems to be easily explained when studying the formation of Uranus and Neptune (Helled & Bodenheimer 2014;Valletta & Helled 2022). The authors demonstrate that slight changes in the protoplanetary disk and the environment of the planetary embryos (e.g., core accretion rate, solid surface density) lead to planets with greater differences in mass and composition.…”

Section: Toi-5678 B Within the Exoplanet Populationmentioning

confidence: 99%

TOI-5678b: A 48-day transiting Neptune-mass planet characterized with CHEOPS and HARPS

Ulmer-Moll,

Osborn,

Tuson

et al. 2023

A&A

View full text Add to dashboard Cite

Context. A large sample of long-period giant planets has been discovered thanks to long-term radial velocity surveys, but only a few dozen of these planets have a precise radius measurement. Transiting gas giants are crucial targets for the study of atmospheric composition across a wide range of equilibrium temperatures and, more importantly, for shedding light on the formation and evolution of planetary systems. Indeed, compared to hot Jupiters, the atmospheric properties and orbital parameters of cooler gas giants are unaltered by intense stellar irradiation and tidal effects. Aims. We aim to identify long-period planets in the Transiting Exoplanet Survey Satellite (TESS) data as single or duo-transit events. Our goal is to solve the orbital periods of TESS duo-transit candidates with the use of additional space-based photometric observations and to collect follow-up spectroscopic observations in order to confirm the planetary nature and measure the mass of the candidates. Methods. We use the CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability period aliases in order to discard or confirm a transit event at a given period. Once a period is confirmed, we jointly model the TESS and CHEOPS light curves along with the radial velocity datasets to measure the orbital parameters of the system and obtain precise mass and radius measurements. Results. We report the discovery of a long-period transiting Neptune-mass planet orbiting the G7-type star TOI-5678. Our spectroscopic analysis shows that TOI-5678 is a star with a solar metallicity. The TESS light curve of TOI-5678 presents two transit events separated by almost two years. In addition, CHEOPS observed the target as part of its Guaranteed Time Observation program. After four non-detections corresponding to possible periods, CHEOPS detected a transit event matching a unique period alias. Follow-up radial velocity observations were carried out with the ground-based high-resolution spectrographs CORALIE and HARPS. Joint modeling reveals that TOI-5678 hosts a 47.73 day period planet, and we measure an orbital eccentricity consistent with zero at 2σ. The planet TOI-5678 b has a mass of 20 ± 4 Earth masses (M⊕) and a radius of 4.91 ± 0.08 R⊕ Using interior structure modeling, we find that TOI-5678 b is composed of a low-mass core surrounded by a large H/He layer with a mass of 3.2±1.7−1.3 M⊕. Conclusions. TOI-5678 b is part of a growing sample of well-characterized transiting gas giants receiving moderate amounts of stellar insolation (11 S⊕). Precise density measurement gives us insight into their interior composition, and the objects orbiting bright stars are suitable targets to study the atmospheric composition of cooler gas giants.

show abstract

“…Indeed, Saturn interior models imply that Saturn has an extended fuzzy core (e.g., Mankovich & Fuller 2021;Nettelmann et al 2021). The delay of gas accretion by a few million years and the transition to a gas giant planet at a higher mass also naturally explain why Uranus and Neptune are heavy-element dominated in composition (e.g., Valletta & Helled 2022;) -as indicated by Fig. 1 (bottom panel), at a planetary mass of ∼15 M ⊕ , the H-He mass fraction is about 10%.…”

Section: Slow Giant Planet Formation and Delayed Runaway Gas Accretionmentioning

confidence: 99%

The mass of gas giant planets: Is Saturn a failed gas giant?

Helled

2023

A&A

Self Cite

View full text Add to dashboard Cite

The formation history of giant planets inside and outside the Solar System remains unknown. We suggest that runaway gas accretion is initiated only at a mass of ∼100 M⊕ and that this mass corresponds to the transition to a gas giant, a planet whose composition is dominated by hydrogen and helium. Delayed runaway accretion (by a few million years) and having it occurring at higher masses is likely a result of an intermediate stage of efficient heavy-element accretion (at a rate of ∼10−5 M⊕ yr−1) that provides sufficient energy to hinder rapid gas accretion. This may imply that Saturn has never reached the stage of runaway gas accretion and that it is a “failed giant planet”. The transition to a gas giant planet above Saturn’s mass naturally explains the differences between the bulk metallicities and internal structures of Jupiter and Saturn. The mass at which a planet transitions to a gas giant planet strongly depends on the exact formation history and birth environment of the planet, which are still not well constrained for our Solar System. In terms of giant exoplanets, the occurrence of runaway gas accretion at planetary masses greater than Saturn’s can explain the transitions in the mass-radius relations of observed exoplanets and the high metallicity of intermediate-mass exoplanets.

show abstract

Possible In Situ Formation of Uranus and Neptune via Pebble Accretion

Cited by 9 publications

References 57 publications

Exoplanet interior retrievals: core masses and metallicities from atmospheric abundances

Exoplanet interior retrievals: core masses and metallicities from atmospheric abundances

TOI-5678b: A 48-day transiting Neptune-mass planet characterized with CHEOPS and HARPS

The mass of gas giant planets: Is Saturn a failed gas giant?

Contact Info

Product

Resources

About