Exoplanets & Exomoons

The Stability Of Unevenly Spaced Planetary Systems

By Keith Cowing
Status Report
September 1, 2023
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The Stability Of Unevenly Spaced Planetary Systems
(a) The median orbit crossing time over 500 runs of simulations for different Δ and 𝑓. For large separations (Δ > 8), the median of 40 runs is shown. The closest separation pairs are assumed to be the innermost pairs. The solid lines correspond to least-squares fitting. The fitting of previous study for the uniformly separated case is shown by the black dotted line. (b) Relationship between the first close encounter pair and the initial closest pair for 𝑓 = 0.6. (c) Relationship between the first colliding pair and the initial closest pair for 𝑓 = 0.6. (d) Relationship between the orbit crossing time of the system and the semimajor axis of the closest pair. The solid line is measured in years, and the dashed line is measured in the Keplerian orbital period of the closest pair. — astro-ph.EP

Studying the orbital stability of multi-planet systems is essential to understand planet formation, estimate the stable time of an observed planetary system, and advance population synthesis models.

Although previous studies have primarily focused on ideal systems characterized by uniform orbital separations, in reality a diverse range of orbital separations exists among planets within the same system. This study focuses on investigating the dynamical stability of systems with non-uniform separation.

We considered a system with 10 planets with masses of 10−7 solar masses around a central star with a mass of 1 solar mass. We performed more than 100,000 runs of N-body simulations with different parameters. Results demonstrate that reducing merely one pair of planetary spacing leads to an order of magnitude shorter orbital crossing times that could be formulated based on the Keplerian periods of the closest separation pair.

Furthermore, the first collisions are found to be closely associated with the first encounter pair that is likely to be the closest separation pair initially. We conclude that when estimating the orbital crossing time and colliding pairs in a realistic situation, updating the formula derived for evenly spaced systems would be necessary.

Sheng Yang, Liangyu Wu, Zekai Zheng, Masahiro Ogihara, Kangrou Guo, Wenzhan Ouyang, Yaxing He

Comments: 6 pages, 3 figures, accepted for publication in Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2308.16798 [astro-ph.EP] (or arXiv:2308.16798v1 [astro-ph.EP] for this version)
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Journal reference: Icarus, Volume 406, 2023, 115757
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Submission history
From: Sheng Yang
[v1] Thu, 31 Aug 2023 15:20:32 UTC (135 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻