Resonant structures in exozodiacal clouds created by exo-Earths in the habitable zone of late-type stars

¹ Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
² SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea

^★ Corresponding authors: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 6 August 2025
Accepted: 13 April 2026

Abstract

Context. Earth-like exoplanets can create resonant structures in exozodiacal dust through mean motion resonances. These structures not only suggest the presence of such planets but also act as potential noise sources in future mid-infrared nulling interferometry observations.

Aims. We aim to investigate how resonant structures in exozodiacal dust vary across stellar spectral types (F4-M4) and evaluate how stellar wind drag affects their morphology and brightness in mature planetary systems.

Methods. We conducted numerical simulations of dust dynamics, extending earlier studies by including spectral-type variation in stellar wind drag in addition to Poynting-Robertson (PR) drag. Our models represent systems of a few gigayears hosting an Earth-like exoplanet in the habitable zone. We produced spatially resolved maps of optical depth and thermal emission for different stellar spectral types.

Results. Our simulations show that resonant ring structures form for all stellar spectral types considered. In particular, we find that stellar wind drag plays a critical role in shaping dust dynamics around old M-type stars, where it could dominate over PR drag by a factor of approximately 44. This reduces the contrast of resonant rings relative to the background disk compared to cases with a stellar wind fixed at the solar value. Across spectral types, the geometric optical depth contrast for resonant rings increases toward lower-mass stars, assuming a background level fixed at 3 zodis. Our calculations show that the optical depth and thermal emission distributions at 10 μm are asymmetric in resonant rings, and we quantified the resulting magnitude of asymmetric brightness.

Conclusions. Our findings highlight the importance of incorporating both resonant dynamics and stellar wind effects when modeling exozodiacal dust around stars of different spectral types.