SETI & Technosignatures

Constellations of co-orbital planets: horseshoe dynamics, long-term stability, transit timing variations, and potential as SETI beacons

By Keith Cowing
April 21, 2023
Filed under , , ,
Constellations of co-orbital planets: horseshoe dynamics, long-term stability, transit timing variations, and potential as SETI beacons
Example of a 2- (left), 3- (center) and 4-planet (right) horseshoe systems. In each case the planets are 1 M⊕. Top: The libration of the planets seen in a co-moving frame, with the radial excursion of each planet expanded by a factor of 10 to improve visibility. Bottom: The distance between the two planets (measured in both au and mutual Hill radii) and their orbital semimajor axes, both as a function of time. During each close approach between the two planets, the exchange in energy causes an orbital flip in semimajor axis. The small wobbles along some of the horseshoes are at the orbital frequency and come from misalignments in pericenter at the time of encounter (as shown by Dermott & Murray 1981b). — astro-ph.EP

Co-orbital systems contain two or more bodies sharing the same orbit around a planet or star. The best-known flavors of co-orbital systems are tadpoles (in which two bodies’ angular separations oscillate about the L4/L5 Lagrange points 60∘ apart) and horseshoes (with two bodies periodically exchanging orbital energy to trace out a horseshoe shape in a co-rotating frame).

Here, we use N-body simulations to explore the parameter space of many-planet horseshoe systems. We show that up to 24 equal-mass, Earth-mass planets can share the same orbit at 1 au, following a complex pattern in which neighboring planets undergo horseshoe oscillations. We explore the dynamics of horseshoe constellations, and show that they can remain stable for billions of years and even persist through their stars’ post-main sequence evolution.

With sufficient observations, they can be identified through their large-amplitude, correlated transit timing variations. Given their longevity and exotic orbital architectures, horseshoe constellations may represent potential SETI beacons.

Sean N. Raymond, Dimitri Veras, Matthew S. Clement, Andre Izidoro, David Kipping, Victoria Meadows

Comments: 10 pages, 10 figures. Published in MNRAS. YouTube playlist with animations of horseshoe constellation systems here: this https URL . Blog post here: this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2304.09209 [astro-ph.EP](or arXiv:2304.09209v1 [astro-ph.EP] for this version)
Journal reference: Monthly Notices of the Royal Astronomical Society, Volume 521, Issue 2, pp.2002-2011
Related DOI:
Focus to learn more
Submission history
From: Sean Raymond
[v1] Tue, 18 Apr 2023 18:01:48 UTC (2,799 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) 🖖🏻