English

Where Do Hot Jupiters Come From? Revisiting Tidal Disruption and Ejection in High-Eccentricity Migration

Earth and Planetary Astrophysics 2026-05-15 v1

Abstract

The origin of hot Jupiters remains a key open question. In the high-eccentricity migration scenario, traditional coreless models predict a strict tidal exclusion zone within 2.7\sim 2.7 tidal radii rtr_\textrm{t}, in which giant planets are either fully disrupted or ejected. We revisit this limit using three-dimensional hydrodynamic simulations of giant planets with realistic dense cores (10 - 20 MM_\oplus). We find that even a few-percent-mass core fundamentally changes the outcome: \textbf{no total disruptions} occur within the previously suggested destruction zone (2.7rt\lesssim 2.7 \, r_\textrm{t}). For deep encounters (1.7rt\lesssim 1.7 \, r_\textrm{t}) planets suffer severe envelope stripping and are either progressively downsized to dense remnants or ejected after a few close encounters, possibly contributing to the free-floating planet population. In the intermediate regime (1.7 \sim 1.7 --2.0,rt2.0, r_\mathrm{t}), planets experience significant partial mass loss over repeated encounters. For wider encounters (2.0rt \gtrsim 2.0\, r_\mathrm{t} ), mass loss is minimal, allowing the planets gradually circularize into hot Jupiters. Furthermore, we show that for highly eccentric orbits (e0.9e\gtrsim 0.9), the change in specific orbital energy ΔEorb \Delta E_{\mathrm{orb}} depends primarily on periastron distance rp r_\mathrm{p} rather than semi-major axis a a . This enables us to extrapolate our fixed-a a results across a broad (aa, ee) parameter space and identify a well-defined tidal ejection zone whose sharp boundaries converge asymptotically. Our results highlight the crucial role of planetary internal structure in high-eccentricity migration and suggest that the survival and transformation of core-bearing giant planets are far more common than previously thought.

Keywords

Cite

@article{arxiv.2605.14433,
  title  = {Where Do Hot Jupiters Come From? Revisiting Tidal Disruption and Ejection in High-Eccentricity Migration},
  author = {Qianli Fan and Shang-Fei Liu},
  journal= {arXiv preprint arXiv:2605.14433},
  year   = {2026}
}

Comments

17 pages, 6 figures, accepted for publication in The Astrophysical Journal Letters