发现系外行星的生长历史：土星类似物HD 149026 b
Discovering the Growth Histories of Exoplanets: The Saturn Analog HD 149026b
摘要：
凌日的“热土星”HD 149026 b，在海王星-木星质量范围内的任何已确认行星中具有最高的平均密度，自2005年发现以来，它已经挑战了行星形成的理论。以前的研究无法解释这颗行星45-110地球质量的固体核心的起源，而不会引发灾难，如气体巨星碰撞或邻近行星发射的重星子轰击。在这里，我们表明，HD 149026 b的大核心可以成功地解释了标准的核心吸积理论的行星形成。我们重建HD 149026 b的关键是：（1）应用太阳星云模型来描述原行星托儿所;（2）将行星最初放置在土星日心距离9.5 AU的长周期轨道上;（3）根据恒星的重元素富集度将HD 149026盘中的固体质量调整为太阳星云的两倍。我们表明，行星的迁移到其当前的轨道在0.042 AU是符合我们的形成模型。我们对HD 149026 b的研究表明，有可能发现任何具有明确核心质量的行星的生长历史，这些行星围绕太阳型恒星运行。
英文摘要：
The transiting "hot Saturn" HD 149026b, which has the highest mean density of any confirmed planet in the Neptune-Jupiter mass range, has challenged theories of planet formation since its discovery in 2005. Previous investigations could not explain the origin of the planet's 45-110 Earth-mass solid core without invoking catastrophes such as gas giant collisions or heavy planetesimal bombardment launched by neighboring planets. Here we show that HD 149026b's large core can be successfully explained by the standard core accretion theory of planet formation. The keys to our reconstruction of HD 149026b are (1) applying a model of the solar nebula to describe the protoplanet nursery; (2) placing the planet initially on a long-period orbit at Saturn's heliocentric distance of 9.5 AU; and (3) adjusting the solid mass in the HD 149026 disk to twice that of the solar nebula in accordance with the star's heavy element enrichment. We show that the planet's migration into its current orbit at 0.042 AU is consistent with our formation model. Our study of HD 149026b demonstrates that it is possible to discover the growth history of any planet with a well-defined core mass that orbits a solar-type star.
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