Warm giant exoplanet characterisation: current state, challenges and outlook

Müller, Simon; Helled, Ravit

doi:10.3389/fspas.2023.1179000

Cited by 9 publications

(2 citation statements)

References 96 publications

(107 reference statements)

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“…Finally, a Saturn probe would allow us to do a comparative analysis of Jupiter's and Saturn's atmospheres and identify whether it is also the case for Saturn that there is tension between the atmospheric composition and interior models. Similarly, accurate measurements of the atmospheric composition of a large number of giant exoplanets, together with estimates of the planetary bulk composition, would provide a more global view of the relation between the atmospheric and bulk compositions of giant planets (Helled et al 2022c;Müller & Helled 2023).…”

Section: Discussionmentioning

confidence: 99%

Can Jupiter’s Atmospheric Metallicity Be Different from the Deep Interior?

Müller,

Helled

2024

ApJ

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Updated formation and structure models of Jupiter predict a metal-poor envelope. This is at odds with the two to three times solar metallicity measured by the Galileo probe. Additionally, Juno data imply that water and ammonia are enriched. Here, we explore whether Jupiter could have a deep radiative layer separating the atmosphere from the deeper interior. The radiative layer could be caused by a hydrogen-transparency window or depletion of alkali metals. We show that heavy-element accretion during Jupiter’s evolution could lead to the desired atmospheric enrichment and that this configuration would be stable over billions of years. The origin of the heavy elements could be cumulative small impacts or one large impact. The preferred scenario requires a deep radiative zone, due to a local reduction of the opacity at ∼2000 K by ∼90%, which is supported by Juno data, and vertical mixing through the boundary with an efficiency similar to that of molecular diffusion (D ≲ 10−2 cm2 s−1). Therefore, most of Jupiter’s molecular envelope could have solar composition while its uppermost atmosphere is enriched with heavier elements. The enrichment likely originates from the accretion of solid objects. This possibility resolves the long-standing mismatch between Jupiter’s interior models and atmospheric composition measurements. Furthermore, our results imply that the measured atmospheric composition of exoplanets does not necessarily reflect their bulk compositions. We also investigate whether the enrichment could be due to the erosion of a dilute core and show that this is highly unlikely. The core-erosion scenario is inconsistent with evolution calculations, the deep radiative layer, and published interior models.

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Section: Discussionmentioning

confidence: 99%

Can Jupiter’s Atmospheric Metallicity Be Different from the Deep Interior?

Müller,

Helled

2024

ApJ

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“…We model the long-term evolution of gas giant planets using the code "Modules for Experiments in Stellar Astrophysics" (MESA, Paxton et al 2010Paxton et al , 2013Paxton et al , 2015Paxton et al , 2018Paxton et al , 2019Jermyn et al 2023). To simulate convective mixing properly, we built on the improvements presented by (see also Müller & Helled 2021;Müller & Helled 2023a) and extended MESA's capabilities to calculate the planetary evolution in three major ways.…”

Section: Planetary Evolution With Convective Mixingmentioning

confidence: 99%

Constraining the origin of giant exoplanets via elemental abundance measurements

Knierim

Shibata

Helled

2022

A&A

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The origin of close-in giant planets is a key open question in planet formation theory. The two leading models are (i) formation at the outer disk followed by migration and (ii) in situ formation. In this work we determine the atmospheric composition of warm Jupiters for both formation scenarios. We perform N-body simulations of planetesimal accretion interior and exterior to the water ice-line for various planetary formation locations, planetary masses, and planetesimal sizes to estimate the accreted heavy-element mass and final planetary composition. We find that the two models differ significantly: migrating giant planets have 2–14 times higher metallicities than planets that form in situ. The ratio between refractories and volatiles is found to be above one for migrating planets but below 0.4 for planets that form in situ. We also identify very different trends between heavy-element enrichment and planetary mass for these two formation mechanisms. While the metallicity of migrating planets is found to increase with decreasing planetary mass, it is about constant for in situ formation. Our study highlights the importance of measuring the atmospheric composition of warm Jupiters and its connection to their formation and evolutionary paths.

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The GAPS programme at TNG

Mantovan,

Malavolta,

Desidera

et al. 2024

A&A

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Short-period giant planets ($P$\,lesssim \,10 days p J $) are frequently found to be solitary compared to other classes of exoplanets. Small inner companions to giant planets with $P$\,lesssim \,15 days are known only in five compact systems: WASP-47, Kepler-730, WASP-132, TOI-1130, and TOI-2000. Here, we report the confirmation of TOI-5398, the youngest known compact multi-planet system composed of a hot sub-Neptune (TOI-5398 c c $\,=\,4.77271 days) orbiting interior to a short-period Saturn (TOI-5398 b b $\,=\,10.590547 days) planet, both transiting around a 650\,pm \,150 Myr G-type star. As part of the Global Architecture of Planetary Systems (GAPS) Young Object project, we confirmed and characterised this compact system, measuring the radius and mass of both planets, thus constraining their bulk composition. Using multi-dimensional Gaussian processes, we simultaneously modelled stellar activity and planetary signals from the Transiting Exoplanet Survey Satellite ( TESS ) Sector 48 light curve and our High Accuracy Radial velocity Planet Searcher (HARPS-N) radial velocity (RV) time series. We confirmed the planetary nature of both planets, TOI-5398 b and TOI-5398 c, and obtained a precise estimation of their stellar parameters. Through the use of astrometric, photometric, and spectroscopic observations, our findings indicate that TOI-5398 is a young, active G dwarf star (650\,pm \,150 Myr) with a rotational period of rot $\,=\,7.34 days. The transit photometry and RV measurements enabled us to measure both the radius and mass of planets b, $R_b$\,=\,10.30pm 0.40 oplus $, $M_b$\,=\,58.7pm 5.7 oplus $, and c, $R_c$\,=\,3.52\,pm \,0.19 oplus $, $M_c$\,=\,11.8pm 4.8 oplus TESS observed TOI-5398 during sector 48 and no further observations are planned in the current Extended Mission, making our ground-based light curves crucial for improvement of the ephemeris. With a transmission spectroscopy metric (TSM) value of around 300, TOI-5398 b is the most amenable warm giant (10\,<\,$P$\,<\,100 days) for JWST atmospheric characterisation.

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Warm giant exoplanet characterisation: current state, challenges and outlook

Cited by 9 publications

References 96 publications

Can Jupiter’s Atmospheric Metallicity Be Different from the Deep Interior?

Can Jupiter’s Atmospheric Metallicity Be Different from the Deep Interior?

Constraining the origin of giant exoplanets via elemental abundance measurements

The GAPS programme at TNG

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