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A Formation-stage Bottleneck for Exomoons around Close-in Rocky Planets

Year: 2026

Type: article

Abstract: Massive moons around rocky exoplanets are expected outcomes of giant impacts, yet no exomoon has been securely confirmed. We address this problem using meshless finite-mass (MFM) simulations of giant impacts between differentiated rocky planets that include stellar tidal and Coriolis forces in a local corotating frame for orbital periods of 1–300 days, and compare these simulations with otherwise identical collisions in isolation. We find that stellar perturbations impose a severe formation-stage bottleneck on moon-forming disks. Ultra-short-period impacts leave essentially no surviving circumplanetary disk (CPD), whereas 10 day systems retain only strongly depleted, radially truncated, and dynamically compact disks. High impact velocities, expected for close-in planets, are devastating for disk generation, while retrograde impacts can slightly compensate for disk mass depletion. These results show that stellar perturbations can suppress exomoon formation around close-in rocky planets, reshaping expectations for the demographics of exomoons.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/aea8fc

Authors: Rongxi Bi, Hongping Deng, Christian Reinhardt, Shangfei Liu, Yun Liu

Institutions: Chengdu University of Technology, Chinese Academy of Sciences, University of Bern, University of Zurich, Sun Yat-sen University

Language: English

Topic: Astro and Planetary Science

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,499

OpenAlex ID: W7196974142

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