Coupled Planetary Interior and Tidal Evolution

Fuente: arXiv
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Main Authors: Hallatt, Tim, Millholland, Sarah
Format: Preprint
Published: 2025
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author Hallatt, Tim
Millholland, Sarah
author_facet Hallatt, Tim
Millholland, Sarah
contents We present a new planetary structure/thermal evolution model, designed for use in problems that couple orbital dynamics with planetary structure. We first benchmark our structural/thermal evolution calculations against the \texttt{MESA} stellar evolution code, finding excellent agreement across a wide range of planet mass, equilibrium temperature, entropy, and extra heating deposited at various depths in the planet. We then apply our method to study the tidal migration histories of Neptunes in the recently identified ``ridge" (periods ${\sim}3{-}6$ days), a feature that has been suggested to be populated via high eccentricity migration (HEM) of more distant Neptunes. We find that it is difficult to form a circularized Neptune in the ridge without instigating runaway tidal inflation and likely atmospheric destruction; low eccentricity Neptunes in the ridge can only be emplaced by HEM if they are metal-rich and exhibit finely-tuned tidal quality factors. If follow-up observations confirm that low eccentricity Neptunes in the ridge did arrive via HEM and are not strongly enriched in metals, our calculations indicate that their tidal heating mechanism must operate in the upper reaches of the planet to avoid runaway inflation. Gravity modes excited in upper radiative layers are a possible candidate mechanism, while friction in the core or turbulent dissipation in convective zones could be ruled out.
format Preprint
id arxiv_https___arxiv_org_abs_2509_22923
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Coupled Planetary Interior and Tidal Evolution
Hallatt, Tim
Millholland, Sarah
Earth and Planetary Astrophysics
We present a new planetary structure/thermal evolution model, designed for use in problems that couple orbital dynamics with planetary structure. We first benchmark our structural/thermal evolution calculations against the \texttt{MESA} stellar evolution code, finding excellent agreement across a wide range of planet mass, equilibrium temperature, entropy, and extra heating deposited at various depths in the planet. We then apply our method to study the tidal migration histories of Neptunes in the recently identified ``ridge" (periods ${\sim}3{-}6$ days), a feature that has been suggested to be populated via high eccentricity migration (HEM) of more distant Neptunes. We find that it is difficult to form a circularized Neptune in the ridge without instigating runaway tidal inflation and likely atmospheric destruction; low eccentricity Neptunes in the ridge can only be emplaced by HEM if they are metal-rich and exhibit finely-tuned tidal quality factors. If follow-up observations confirm that low eccentricity Neptunes in the ridge did arrive via HEM and are not strongly enriched in metals, our calculations indicate that their tidal heating mechanism must operate in the upper reaches of the planet to avoid runaway inflation. Gravity modes excited in upper radiative layers are a possible candidate mechanism, while friction in the core or turbulent dissipation in convective zones could be ruled out.
title Coupled Planetary Interior and Tidal Evolution
topic Earth and Planetary Astrophysics
url https://arxiv.org/abs/2509.22923