Testing the prevalence of hydrogen-silicate miscibility in young sub-Neptunes
Abstract
Hydrogen-silicate miscibility can significantly alter the interior structure and thermal evolution of sub-Neptunes. We consider the interplay between this miscibility and stellar-driven atmospheric escape. We find that, for the first ∼ 100 Myr, sub-Neptunes store most of their hydrogen content within their miscible interiors, protecting it from escape. As hydrogen is removed from the top of the atmosphere, more hydrogen is exsolved from the miscible interior, resupplying the envelope mass and delaying the planet's contraction when compared with models that do not account for miscibility. We construct a population-level Bayesian hierarchical inference model which tests for the prevalence of fully miscible sub-Neptunes. With conservative measurement uncertainty and no completeness corrections, we predict that ∼ 100−200 observed young sub-Neptunes with measured radii, masses and ages ≲ 1 Gyr are required to differentiate between fully miscible and immiscible models. This survey size requirement decreases with improved measurement uncertainty. Furthermore, one can reliably infer the underlying distributions of planetary initial conditions if completeness corrections are included in the analysis.
Related
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BibTeX
@misc{rogers2026testing,
title = {{Testing the prevalence of hydrogen-silicate miscibility in young sub-Neptunes}},
author = {James G. Rogers and Hilke E. Schlichting},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.30644},
eprint = {2606.30644},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.30644},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Testing the prevalence of hydrogen-silicate miscibility in young sub-Neptunes
AU - James G. Rogers
AU - Hilke E. Schlichting
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2606.30644
UR - https://arxiv.org/abs/2606.30644
AB - Hydrogen-silicate miscibility can significantly alter the interior structure and thermal evolution of sub-Neptunes. We consider the interplay between this miscibility and stellar-driven atmospheric escape. We find that, for the first ∼ 100 Myr, sub-Neptunes store most of their hydrogen content within their miscible interiors, protecting it from escape. As hydrogen is removed from the top of the atmosphere, more hydrogen is exsolved from the miscible interior, resupplying the envelope mass and delaying the planet's contraction when compared with models that do not account for miscibility. We construct a population-level Bayesian hierarchical inference model which tests for the prevalence of fully miscible sub-Neptunes. With conservative measurement uncertainty and no completeness corrections, we predict that ∼ 100−200 observed young sub-Neptunes with measured radii, masses and ages ≲ 1 Gyr are required to differentiate between fully miscible and immiscible models. This survey size requirement decreases with improved measurement uncertainty. Furthermore, one can reliably infer the underlying distributions of planetary initial conditions if completeness corrections are included in the analysis.
ER -