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Effect of non-adiabatic thermal profiles on the inferred compositions of Uranus and Neptune


Podolak, Morris; Helled, Ravit; Schubert, Gerald (2019). Effect of non-adiabatic thermal profiles on the inferred compositions of Uranus and Neptune. Monthly Notices of the Royal Astronomical Society, 487(2):2653-2664.

Abstract

It has been a common assumption of interior models that the outer planets of our Solar system are convective, and that the internal temperature distributions are therefore adiabatic. This assumption is also often applied to exoplanets. However, if a large portion of the thermal flux can be transferred by conduction, or if convection is inhibited, the thermal profile could be substantially different and would therefore affect the inferred planetary composition. Here we investigate how the assumption of non-adiabatic temperature profiles in Uranus and Neptune affects their internal structures and compositions. We use a set of plausible temperature profiles together with density profiles that match the measured gravitational fields to derive the planets’ compositions. We find that the inferred compositions of both Uranus and Neptune are quite sensitive to the assumed thermal profile in the outer layers, but relatively insensitive to the thermal profile in the central, high-pressure region. The overall value of the heavy element mass fraction, Z, for these planets is between 0.8 and 0.9. Finally, we suggest that large parts of Uranus’ interior might be conductive, a conclusion that is consistent with Uranus dynamo models and a hot central inner region.

Abstract

It has been a common assumption of interior models that the outer planets of our Solar system are convective, and that the internal temperature distributions are therefore adiabatic. This assumption is also often applied to exoplanets. However, if a large portion of the thermal flux can be transferred by conduction, or if convection is inhibited, the thermal profile could be substantially different and would therefore affect the inferred planetary composition. Here we investigate how the assumption of non-adiabatic temperature profiles in Uranus and Neptune affects their internal structures and compositions. We use a set of plausible temperature profiles together with density profiles that match the measured gravitational fields to derive the planets’ compositions. We find that the inferred compositions of both Uranus and Neptune are quite sensitive to the assumed thermal profile in the outer layers, but relatively insensitive to the thermal profile in the central, high-pressure region. The overall value of the heavy element mass fraction, Z, for these planets is between 0.8 and 0.9. Finally, we suggest that large parts of Uranus’ interior might be conductive, a conclusion that is consistent with Uranus dynamo models and a hot central inner region.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Scopus Subject Areas:Physical Sciences > Astronomy and Astrophysics
Physical Sciences > Space and Planetary Science
Language:English
Date:1 August 2019
Deposited On:13 Feb 2020 15:57
Last Modified:29 Jul 2020 13:44
Publisher:Oxford University Press
ISSN:0035-8711
Additional Information:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2019 The Authors. Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/mnras/stz1467
Project Information:
  • : FunderSNSF
  • : Grant ID200021-100005
  • : Project TitleNeural network statistical estimation for very broad coverage parsing
  • : FunderSNSF
  • : Grant ID200021_169054
  • : Project TitleSolar and Extrasolar Giant Planets: Formation, Evolution, and Internal Structure

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