Exoplanets & Exomoons

Bound Circumplanetary Orbits Under The Influence Of Radiation Pressure: Application To Dust In Directly Imaged Exoplanet Systems

By Keith Cowing
Status Report
August 16, 2023
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Bound Circumplanetary Orbits Under The Influence Of Radiation Pressure: Application To Dust In Directly Imaged Exoplanet Systems
All orbits in this figure are equilibria for the case µ = 0.001, β = 0.1 and with starting condition ξ(0) = −1.9 and ˙ξ = 0. The value of CH is different, however. In the left hand panel, the black curve represents the F family, and the red curve indicates the leftmost intersection of the G′′ family. Finally, the blue and cyan curves represent two incarnations of the C family. The right-hand panel shows two incarnations each of the G′′ family (blue and cyan) and the F ′family (red and magenta). Also show, as crosses, are the stationary points of the potential. The equivalents of the L4 and L5 points are responsible for the doubling of the orbital families, as can be seen by the loops induced in the red and blue curves. — astro-ph.EP

We examine the population of simply periodic orbits in the Hill problem with radiation pressure included, in order to understand the distribution of gravitationally bound dust in orbit around a planet.

We study a wide range of radiation pressure strengths, which requires the inclusion of additional terms beyond those discussed in previous analyses of this problem. In particular, our solutions reveal two distinct populations of stable wide, retrograde, orbits, as opposed to the single family that exists in the purely gravitational problem.

We use the result of these calculations to study the observational shape of dust populations bound to extrasolar planets, that might be observable in scattered or reradiated light. In particular, we find that such dusty clouds should be elongated along the star–planet axis, and that the elongation of the bound population increases with β, a measure of the strength of the radiation pressure.

As an application of this model, we consider the properties of the Fomalhaut system. The unusual orbital properties of the object Fomalhaut~b can be explained if the observed light was scattered by dust that was released from an object in a quasi-satellite orbit about a planet located in, or near, the observed debris ring. Within the context of the model of Hayakawa \& Hansen (2023), we find that the dust cloud around such a planet is still approximately an order of magnitude fainter than the limits set by current JWST data.

Brad M. S. Hansen, Kevin Hayakawa

Comments: 21 pages, 23 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2308.07994 [astro-ph.EP] (or arXiv:2308.07994v1 [astro-ph.EP] for this version)
Submission history
From: Brad Hansen
[v1] Tue, 15 Aug 2023 18:59:11 UTC (10,371 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) 🖖🏻