Different Inhomogeneous Evolutionary Histories for Uranus and Neptune

We present updated nonadiabatic and inhomogeneous evolution models for Uranus and Neptune, employing an interior composition of methane, ammonia, water, and rocks. Following the formation trends of the gas giants, Uranus and Neptune formation models are applied, where both planets begin with layers...

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Main Author: Roberto Tejada Arevalo
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal Letters
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Online Access:https://doi.org/10.3847/2041-8213/adf3a5
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author Roberto Tejada Arevalo
author_facet Roberto Tejada Arevalo
author_sort Roberto Tejada Arevalo
collection DOAJ
description We present updated nonadiabatic and inhomogeneous evolution models for Uranus and Neptune, employing an interior composition of methane, ammonia, water, and rocks. Following the formation trends of the gas giants, Uranus and Neptune formation models are applied, where both planets begin with layers stable to convection. Both planets are subject to convective mixing throughout their evolution. Consistent with past work on this subject, the interior heat of Uranus evolution models is preserved by the stability of an outer composition gradient at lower initial entropy, where convective mixing is inhibited over evolutionary timescales. In contrast, if Neptune’s initial entropy is enough to convectively mix its envelope, it undergoes homogenization and adiabatic cooling of the outer 40% of its envelope. The subsequent release of internal energy during Neptune’s evolution, driven by the convective instability of its primordial outer compositional gradient, accounts for its higher luminosity relative to Uranus. This work proposes that the observed luminosity differences between Uranus and Neptune could be explained by the convective stability of their outer envelopes. The extensive convective mixing in Neptune can lead to a higher metallicity in its outer region compared to Uranus, a feature seen in atmospheric measurements and shown in past interior models of Neptune. Due to Neptune’s more pronounced cooling, our models predict favorable conditions for hydrogen–water immiscibility in its envelope.
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spelling doaj-art-044141bf18d54b4db6af5aa6baf218b02025-08-20T03:41:32ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019892L4010.3847/2041-8213/adf3a5Different Inhomogeneous Evolutionary Histories for Uranus and NeptuneRoberto Tejada Arevalo0https://orcid.org/0000-0001-6708-3427Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA ; arevalo@princeton.eduWe present updated nonadiabatic and inhomogeneous evolution models for Uranus and Neptune, employing an interior composition of methane, ammonia, water, and rocks. Following the formation trends of the gas giants, Uranus and Neptune formation models are applied, where both planets begin with layers stable to convection. Both planets are subject to convective mixing throughout their evolution. Consistent with past work on this subject, the interior heat of Uranus evolution models is preserved by the stability of an outer composition gradient at lower initial entropy, where convective mixing is inhibited over evolutionary timescales. In contrast, if Neptune’s initial entropy is enough to convectively mix its envelope, it undergoes homogenization and adiabatic cooling of the outer 40% of its envelope. The subsequent release of internal energy during Neptune’s evolution, driven by the convective instability of its primordial outer compositional gradient, accounts for its higher luminosity relative to Uranus. This work proposes that the observed luminosity differences between Uranus and Neptune could be explained by the convective stability of their outer envelopes. The extensive convective mixing in Neptune can lead to a higher metallicity in its outer region compared to Uranus, a feature seen in atmospheric measurements and shown in past interior models of Neptune. Due to Neptune’s more pronounced cooling, our models predict favorable conditions for hydrogen–water immiscibility in its envelope.https://doi.org/10.3847/2041-8213/adf3a5Solar system gas giant planetsUranusNeptunePlanetary interiorPlanetary structureAtmospheric evolution
spellingShingle Roberto Tejada Arevalo
Different Inhomogeneous Evolutionary Histories for Uranus and Neptune
The Astrophysical Journal Letters
Solar system gas giant planets
Uranus
Neptune
Planetary interior
Planetary structure
Atmospheric evolution
title Different Inhomogeneous Evolutionary Histories for Uranus and Neptune
title_full Different Inhomogeneous Evolutionary Histories for Uranus and Neptune
title_fullStr Different Inhomogeneous Evolutionary Histories for Uranus and Neptune
title_full_unstemmed Different Inhomogeneous Evolutionary Histories for Uranus and Neptune
title_short Different Inhomogeneous Evolutionary Histories for Uranus and Neptune
title_sort different inhomogeneous evolutionary histories for uranus and neptune
topic Solar system gas giant planets
Uranus
Neptune
Planetary interior
Planetary structure
Atmospheric evolution
url https://doi.org/10.3847/2041-8213/adf3a5
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