The elemental composition of planets is commonly related to their star’s abundances, as they both come from the same reservoir during formation. However, it is estimated that 10–15% of rocky exoplanets have unusually high densities. Zifan Lin and co-authors investigate the hypothesis that these planets are fossil cores of giant planets after they have been stripped bare of their envelope and remained in an enhanced compressed state.

The authors build an iterative analytical model of a giant planet and compute the likelihood that it evolves to a ‘naked’ core. The planet is fully differentiated with an iron core and a mantle, which together form the remaining rocky core and undergo a magma ocean phase while the atmosphere is eroded, and a H/He or water envelope, simulating respectively gas giants and ice giants. The model shows that only one of the 12 known high-density rocky planets (GJ 3929 b) has a probability higher than 20–30% to be a compressed remnant core of a giant planet.

行星的元素组成通常与其恒星的丰度有关，因为它们在形成过程中都来自同一个储层。然而，据估计，10-15% 的岩石系外行星具有异常高的密度。Zifan Lin 和合著者研究了这些行星是巨行星的化石核心的假设，这些行星在被剥去外壳并保持增强压缩状态后。

作者构建了一个巨行星的迭代分析模型，并计算了它演化成“裸露”核心的可能性。这颗行星完全分为铁核和地幔，它们共同形成剩余的岩石核心，并在大气被侵蚀时经历岩浆海洋阶段，以及 H/He 或水包层，分别模拟气态巨行星和冰巨星。该模型显示，在 12 颗已知的高密度岩石行星中，只有一颗 （GJ 3929 b） 是巨行星的压缩残余核心的概率高于 20-30%。