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arXiv 2004.13534astro-ph.EP
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在木星形成模糊核心的挑战

The Challenge of Forming a Fuzzy Core in Jupiter

Simon Müller, Ravit Helled, Andrew Cumming

摘要:

最近的木星结构模型与朱诺重力数据相匹配,表明这颗行星在其内部深处有一个富含重元素的扩展区域,即所谓的稀释/模糊核心。这一发现提出了一个问题,即什么可能的形成途径会导致这种结构。我们模拟木星的形成和长期演变,从失控的气体吸积之前的后期形成开始。我们考虑的形成场景包括原始成分梯度,以及随着原木星迅速获得其气体包层而建立的梯度。然后,我们跟随木星的演变,因为它冷却和收缩,特别关注内部的能量和物质运输。我们发现,我们考虑的情况下,没有导致一个模糊的核心,是兼容的内部结构模型。在所有的情况下,木星的大部分信封成为对流和充分混合后,最多几百万年。这是真的,即使当我们考虑的情况下,气体吸积导致一个寒冷的行星,大量的重元素吸积。因此,它的结论是,这是非常具有挑战性的解释木星的稀释核心从标准的形成模型。我们建议未来的工作应该考虑更复杂的形成途径,以及可能导致木星当前状态内部结构的其他物理过程的建模。

英文摘要:

Recent structure models of Jupiter that match Juno gravity data suggest that the planet harbours an extended region in its deep interior that is enriched in heavy elements, a so-called dilute/fuzzy core. This finding raises the question of what possible formation pathways would lead to such a structure. We model Jupiter's formation and long-term evolution, starting at late-stage formation before runaway gas accretion. The formation scenarios we consider include both primordial composition gradients, as well as gradients that are built as proto-Jupiter rapidly acquires its gaseous envelope. We then follow Jupiter's evolution as it cools down and contracts, with a particular focus on the energy and material transport in the interior. We find that none of the scenarios we consider lead to a fuzzy core that is compatible with interior structure models. In all the cases, most of Jupiter's envelope becomes convective and fully mixed after at most a few million years. This is true even when we consider a case where the gas accretion leads to a cold planet, and large amounts of heavy elements are accreted. It is therefore concluded that it is very challenging to explain Jupiter's dilute core from standard formation models. We suggest that future work should consider more complex formation pathways as well as the modelling of additional physical processes that could lead to Jupiter's current-state internal structure.

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