Tidal Inflation is Stronger for Misaligned Neptune-Sized Planets Than Aligned Ones

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Hauptverfasser: Sethi, Ritika, Millholland, Sarah
Format: Preprint
Veröffentlicht: 2025
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author Sethi, Ritika
Millholland, Sarah
author_facet Sethi, Ritika
Millholland, Sarah
contents Recent observations have revealed an intriguing abundance of polar-orbiting Neptune-sized planets, many of which exhibit unusually inflated radii. While such misaligned orbits point to a complex dynamical history, the connection between their orbital orientations and planetary structures remains poorly understood. In this study, we analyze a sample of 12 misaligned and 12 aligned planets using structure models that incorporate tidal heating. We use various statistical tests to demonstrate with at least $90\%$ confidence that misaligned planets experience more tidally-induced radius inflation compared to aligned planets. This inflation likely stems from their dynamically active histories, which often place them in close-in, eccentric, and highly inclined orbits. We further present a case study of WASP-107~b, an exceptionally inflated polar Neptune, and model its history using a simple coupled orbital and radius evolution approach. Our results place constraints on the planet's tidal quality factor that agree with recent JWST observations.
format Preprint
id arxiv_https___arxiv_org_abs_2506_24100
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Tidal Inflation is Stronger for Misaligned Neptune-Sized Planets Than Aligned Ones
Sethi, Ritika
Millholland, Sarah
Earth and Planetary Astrophysics
Recent observations have revealed an intriguing abundance of polar-orbiting Neptune-sized planets, many of which exhibit unusually inflated radii. While such misaligned orbits point to a complex dynamical history, the connection between their orbital orientations and planetary structures remains poorly understood. In this study, we analyze a sample of 12 misaligned and 12 aligned planets using structure models that incorporate tidal heating. We use various statistical tests to demonstrate with at least $90\%$ confidence that misaligned planets experience more tidally-induced radius inflation compared to aligned planets. This inflation likely stems from their dynamically active histories, which often place them in close-in, eccentric, and highly inclined orbits. We further present a case study of WASP-107~b, an exceptionally inflated polar Neptune, and model its history using a simple coupled orbital and radius evolution approach. Our results place constraints on the planet's tidal quality factor that agree with recent JWST observations.
title Tidal Inflation is Stronger for Misaligned Neptune-Sized Planets Than Aligned Ones
topic Earth and Planetary Astrophysics
url https://arxiv.org/abs/2506.24100