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arXiv 1606.01558astro-ph.EP
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木星和土星的演化和内部结构

The Evolution and Internal Structure of Jupiter and Saturn with Compositional Gradients

A. Vazan, R. Helled, M. Podolak, A. Kovetz

摘要:

气体巨行星的内部结构可能比通常假设的具有绝热温度分布的核心-包络结构更复杂。不同的原始内部结构以及各种物理过程可以导致非均匀的成分分布。非均匀的内部结构对行星的热演化和最终结构有重大影响。在本文中,我们提出了木星和土星的替代结构和演化模型,允许非绝热原始结构和混合的重元素的对流,因为这些行星的发展。我们提出了各种初始成分梯度的行星占的演变,并在土星的情况下,包括形成一个富含氦的区域,作为氦雨的结果。我们调查的稳定性与对流成分梯度的区域,并发现,在土星的氦壳保持稳定,不与其余的信封。在其他情况下,对流混合行星内部,尽管存在成分梯度,导致包层富集重元素。我们表明,木星和土星的非绝热结构(和冷却历史)是可行的。在这种情况下,内部温度比标准绝热模型高得多。我们的结论是,内部结构直接联系到行星的形成和演化历史。在解释即将到来的朱诺号和卡西尼号数据时,应该考虑木星和土星的这些替代内部结构。

英文摘要:

The internal structure of gas giant planets may be more complex than the commonly assumed core-envelope structure with an adiabatic temperature profile. Different primordial internal structures as well as various physical processes can lead to non-homogenous compositional distributions. A non-homogenous internal structure has a significant impact on the thermal evolution and final structure of the planets. In this paper, we present alternative structure and evolution models for Jupiter and Saturn allowing for non-adiabatic primordial structures and the mixing of heavy elements by convection as these planets evolve. We present the evolution of the planets accounting for various initial composition gradients, and in the case of Saturn, include the formation of a helium-rich region as a result of helium rain. We investigate the stability of regions with composition gradients against convection, and find that the helium shell in Saturn remains stable and does not mix with the rest of the envelope. In other cases, convection mixes the planetary interior despite the existence of compositional gradients, leading to the enrichment of the envelope with heavy elements. We show that non-adiabatic structures (and cooling histories) for both Jupiter and Saturn are feasible. The interior temperatures in that case are much higher that for standard adiabatic models. We conclude that the internal structure is directly linked to the formation and evolution history of the planet. These alternative internal structures of Jupiter and Saturn should be considered when interpreting the upcoming Juno and Cassini data.

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