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Young Planets Around Young Accreting Stars: I. Migration and Inner Stalling Orbits

By Keith Cowing
Status Report
astro-ph.EP
May 12, 2025
Filed under , , , , , ,
Young Planets Around Young Accreting Stars: I. Migration and Inner Stalling Orbits
Color-contour visualization of density at the disk midplane (the X-Y plane), combined with a vertical slice (the x-z plane), and a cylindrical segment (ϕ coordinate at r = 1) at time t = 88.35. These three surfaces intersect at the current location of the massive q = 0.01 planet. The adopted mesh structure is also shown as an overlay on the half-cylinder segment. — astro-ph.EP)

Planet migration within inner protoplanetary disks significantly influences exoplanet architectures.

We investigate various migration mechanisms for young planets close to young stars. To quantify the stochastic migration driven by turbulent disks, we incorporate planets into existing 3-D MHD disk simulations of magnetospheric accretion. Besides the stochastic torque, we identify periodic torques from slowly evolving disk substructures farther out.

We quantify these turbulent torques analytically using a modified Gaussian process. Then, using the disk structure in our simulation, we calculate migration timescales of various processes, including the smooth Type I/II migration, planet-star tidal interaction, magnetic dipole-dipole interaction, unipolar induction, and aerodynamical drag with the magnetosphere.

Since our inner MHD turbulent disk reveals a very low surface density (∼0.01 g/cm2), the resulting disk migration is significantly slower than previously estimated. Earth-mass planets have the migration timescale in the inner MHD turbulent disk exceeding the Hubble time, effectively stalling at the deadzone inner boundary (RDZIB).

Only giant planets could migrate inward within the turbulent disk, and may stall at the magnetospheric truncation radius (RT). A simplified planet population synthesis demonstrates that, at the end of the disk phase, all planets around solar-mass stars typically stall at ≲0.1 au since RT∼RDZIB. However, around 2 M⊙ stars, higher-mass planets stall significantly closer to the star compared to low-mass planets, due to RT≪RDZIB.

These results are consistent with recent observations on exoplanet demographics around different types of stars. Finally, turbulence in the low-density disk is unable to break the resonant planets, and thus young planets in resonances may be abundant.

Arturo Cevallos Soto, Zhaohuan Zhu

Comments: 28 pages, 18 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2505.03701 [astro-ph.EP](or arXiv:2505.03701v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.03701
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Submission history
From: Arturo Cevallos Soto
[v1] Tue, 6 May 2025 17:21:16 UTC (8,331 KB)
https://arxiv.org/abs/2505.03701
Astrobiology

Keith Cowing

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) 🖖🏻

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