Graduation Semester and Year
Fall 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Physics and Applied Physics
Department
Physics
First Advisor
Manfred Cuntz
Second Advisor
Nevin Weinberg
Abstract
Although exoplanet detection has long been a central focus in astronomy, growing interest in exomoons has highlighted the increasing need for theoretical frameworks to interpret emerging candidates. Furthermore, while submoons, natural satellites orbiting moons, are not presently observed in the Solar System and remain speculative (e.g., the hypothesized past submoon of Saturn’s Iapetus), their existence is plausible within the context of the complex and diverse architectures now identified across planetary and stellar systems. We develop a generalized framework to assess the orbital stability of exomoons and submoons through comprehensive N-body simulations incorporating both three-body dynamics and tidal interactions, with the aim of supporting and guiding future observational efforts. In this dissertation, I present four studies focused on the orbital stability of exomoons and submoons. In the first study (Patel et al., 2024), we examine F-type star–planet systems to identify planets that spend time within the habitable zones (HZs) of their host stars. This initial statistical analysis identifies 18 such systems, including Kepler-1708b, a candidate host for an exomoon. The second study (Patel et al., 2025a) explores the orbital stability of exomoons and submoons in the Kepler-1708, Kepler-1625, and HD 23079 systems. We identify stability regions for potential exomoons in all three systems, including those corresponding to the observed positions of exomoon candidates Kepler-1625 b-i and Kepler-1708 b-i. Additionally, we include a hypothetical submoon in the Kepler-1625 and HD 23079 systems, finding expected stable regions along with significant secular resonance zones. These analyses contribute to a generalized framework for assessing the stability of future exomoon and submoon candidates, with potential applications to observational planning and interpretation. In the third study (Patel et al., 2025b), we apply this framework to the K2-18 system, known for its biosignature potential, by incorporating tidal effects through the reboundx extension library. Our findings indicate that any exomoons in this system would migrate outward on timescales of a few million years or less, rendering their long-term presence highly unlikely. In the fourth study (Patel et al., 2025c), we extend this analysis to a generalized parameter space of Earth-sized planets orbiting M0 to M4 dwarf stars. We find that Luna-sized moons are unlikely to remain stable in systems with M2 and M4 dwarfs, while only higher-mass planets located in the outer habitable zones of M0 dwarfs appear capable of hosting detectable moons. These latter findings suggest that M dwarfs, the most abundant stellar type, may generally lack long-lived moons, with important implications for observational strategies and moon-based habitability scenarios for planets in these systems.
Keywords
Satellites, Orbital stability, Habitability, Tides, Exoplanetary Systems
Disciplines
Astrophysics and Astronomy
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Patel, Shaan Dharmesh, "ON THE ORBITAL DYNAMICS OF EXOPLANETS, EXOMOONS, AND SUBMOONS" (2025). Physics Dissertations. 185.
https://mavmatrix.uta.edu/physics_dissertations/185
Comments
Thank you to Manfred Cuntz, Nevin Weinberg, and Billy Quarles for their guidance throughout. This work was supported by NSF grant No. AST-2054353 and the U.S. Department of Education GAANN grant.