Planetary engulfment as a solution to solar-model discrepancies and its implications for planetary systems
Makaleler > Tam Makale · 2026
Yazarlar: Mutlu YILDIZ
Monthly Notices of the Royal Astronomical Society, Uluslararası, Wos, 2026, cilt 551
Özet
ABSTRACT Thousands of close-in exoplanets suggest that planetary engulfment may be common during stellar evolution. We investigate whether early accretion of planetary material can resolve discrepancies between standard solar models and observations, including helioseismic sound-speed anomalies, the convection-zone depth, and surface abundances. Using mesa, we model pre-main-sequence accretion of metal-rich material representing planetary engulfment, followed by metal-poor disc accretion associated with planet formation. Model DD1020, combining planetary engulfment and turbulent mixing, provides the best agreement with helioseismic constraints. It favours a super-Earth of mass $\sim 5.6$ ${\rm M}_{\oplus }$ (0.33 $M_{\rm N}$) (Dev Dilek), while related best-fitting models favour $\sim 5$–10 ${\rm M}_{\oplus }$. The dissolved planetary material settles below the convection zone ($m=0.96$–0.973 ${\rm M}_{\odot }$), producing a localized heavy-element enhancement that modifies opacity and internal stratification. Optimized control models with variable mixing-length parameters and turbulent mixing but without engulfment improve the agreement only partially. Bayesian Information Criterion analysis shows that the improvement cannot be explained solely by increased model flexibility. The observed solar lithium depletion can be reproduced if the accreted material is lithium-poor and the engulfed planet has a mass of 4.6–5.8 ${\rm M}_{\oplus }$. We also assess the physical feasibility of engulfment using Roche lobe stability, pressure-dependent planetary structure models, and classical aerodynamic drag and ablation. A compact rocky planet can traverse the solar convective envelope with negligible mass-loss, providing independent support for the proposed scenario.