Stars and planets both form by accreting material from a surrounding disk. Because they grow from the same material, theory predicts that there should be a relationship between their compositions. In this study, we search for a compositional link between rocky exoplanets and their host stars. We estimate the iron-mass fraction of rocky exoplanets from their masses and radii and compare it with the compositions of their host stars, which we assume reflect the compositions of the protoplanetary disks. We find a correlation (but not a 1:1 relationship) between these two quantities, with a slope of >4, which we interpret as being attributable to planet formation processes. Super-Earths and super-Mercuries appear to be distinct populations with differing compositions, implying differences in their formation processes.

中文翻译：

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岩石系外行星与其宿主恒星之间的组成联系

恒星和行星都是通过从周围的圆盘中吸积物质而形成的。因为它们是从相同的材料中生长出来的，所以理论预测它们的成分之间应该存在关系。在这项研究中，我们寻找岩石系外行星与其主恒星之间的成分联系。我们根据岩质系外行星的质量和半径估算其铁质量分数，并将其与主恒星的成分进行比较，我们假设这反映了原行星盘的成分。我们发现这两个量之间存在相关性（但不是 1:1 的关系），斜率 > 4，我们将其解释为可归因于行星形成过程。超级地球和超级水星似乎是具有不同成分的不同种群，这意味着它们的形成过程存在差异。