Resizing the giants: How modelling adiabatic interiors impacts predicted planetary radii

Fuente: arXiv
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Autores principales: Müller, Simon, Helled, Ravit
Formato: Preprint
Publicado: 2026
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author Müller, Simon
Helled, Ravit
author_facet Müller, Simon
Helled, Ravit
contents The interiors of giant planets are commonly assumed to be convective and adiabatic, making the adiabatic temperature gradient a key ingredient in interior and evolution models. Multiple numerically distinct methods exist for computing this gradient, yet their impact on inferred planetary structure and radius has not been systematically assessed. In this letter we investigate how the numerical treatment of adiabatic temperature profiles affects inferred planetary radii and internal structure, comparing different methods for evaluating the adiabatic gradient against a ground-truth isentropic baseline, for both the logarithmic and non-logarithmic forms of the temperature differential equation. Static interior models of a one Jupiter mass planet were computed using a state-of-the-art hydrogen-helium equation of state. We find that the choice of numerical method significantly impacts the inferred interior structure and radius. Using the logarithmic temperature equation, central temperatures deviate by several thousand kelvin and surface radii differ by up to 3.4 per cent, exceeding the 1 per cent precision of current giant exoplanet radius measurements threefold. The non-logarithmic form reduces deviations to below ~1 per cent for most methods. We recommend spline derivatives to evaluate the adiabatic gradient, combined with the non-logarithmic temperature equation. Finite differencing and direct use of tabulated gradients or derivatives should be avoided.
format Preprint
id arxiv_https___arxiv_org_abs_2603_24779
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Resizing the giants: How modelling adiabatic interiors impacts predicted planetary radii
Müller, Simon
Helled, Ravit
Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
The interiors of giant planets are commonly assumed to be convective and adiabatic, making the adiabatic temperature gradient a key ingredient in interior and evolution models. Multiple numerically distinct methods exist for computing this gradient, yet their impact on inferred planetary structure and radius has not been systematically assessed. In this letter we investigate how the numerical treatment of adiabatic temperature profiles affects inferred planetary radii and internal structure, comparing different methods for evaluating the adiabatic gradient against a ground-truth isentropic baseline, for both the logarithmic and non-logarithmic forms of the temperature differential equation. Static interior models of a one Jupiter mass planet were computed using a state-of-the-art hydrogen-helium equation of state. We find that the choice of numerical method significantly impacts the inferred interior structure and radius. Using the logarithmic temperature equation, central temperatures deviate by several thousand kelvin and surface radii differ by up to 3.4 per cent, exceeding the 1 per cent precision of current giant exoplanet radius measurements threefold. The non-logarithmic form reduces deviations to below ~1 per cent for most methods. We recommend spline derivatives to evaluate the adiabatic gradient, combined with the non-logarithmic temperature equation. Finite differencing and direct use of tabulated gradients or derivatives should be avoided.
title Resizing the giants: How modelling adiabatic interiors impacts predicted planetary radii
topic Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2603.24779