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arXiv 2005.08330astro-ph.EP
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巨型行星Sainte的形成

Formation of Giant Planet Satellites

Konstantin Batygin, Alessandro Morbidelli

摘要:

最近的分析表明,巨型行星形成的最后阶段伴随着行星希尔球内部大规模气体回旋流的发展。这个环流为一个环绕行星的圆盘提供能量,这个圆盘粘性地将气态物质排回母星云,使系统保持在准稳定状态。在这里,我们研究了木星和土星的天然卫星的形成在这个新概述的图片的框架。我们首先考虑固体物质的长期演变,并证明,环行星盘可以作为一个全球性的尘埃陷阱,其中$s_{\bullet}\sim0.1-10\,$ mm颗粒实现流体动力学平衡,促进径向上升气流和气动阻力之间的平衡。这一过程导致系统的金属丰度逐渐增加,并最终在固体子盘的外部区域引力破碎成$\mathcal{R}\sim100\,$ km的小卫星时达到高潮。随后,卫星聚集通过成对碰撞进行,但当磁盘驱动的轨道迁移将生长的物体从卫星馈送区移除时,卫星聚集终止。由此产生的卫星形成周期可以重复多次,直到母星云的光蒸发结束。我们的模型和木星和土星卫星的已知属性之间的数值模拟的设想形成的情况下产生令人满意的协议。

英文摘要:

Recent analyses have shown that the concluding stages of giant planet formation are accompanied by the development of large-scale meridional flow of gas inside the planetary Hill sphere. This circulation feeds a circumplanetary disk that viscously expels gaseous material back into the parent nebula, maintaining the system in a quasi-steady state. Here we investigate the formation of natural satellites of Jupiter and Saturn within the framework of this newly outlined picture. We begin by considering the long-term evolution of solid material, and demonstrate that the circumplanetary disk can act as a global dust trap, where $s_{\bullet}\sim0.1-10\,$mm grains achieve a hydrodynamical equilibrium, facilitated by a balance between radial updraft and aerodynamic drag. This process leads to a gradual increase in the system's metallicity, and eventually culminates in the gravitational fragmentation of the outer regions of the solid sub-disk into $\mathcal{R}\sim100\,$km satellitesimals. Subsequently, satellite conglomeration ensues via pairwise collisions, but is terminated when disk-driven orbital migration removes the growing objects from the satellitesimal feeding zone. The resulting satellite formation cycle can repeat multiple times, until it is brought to an end by photo-evaporation of the parent nebula. Numerical simulations of the envisioned formation scenario yield satisfactory agreement between our model and the known properties of the Jovian and Saturnian moons.

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