Formation of Rocky Planets at Extremely Close Separations

Determine whether rocky planets can form at orbital separations interior to the silicate sublimation line, where iron may become more abundant relative to silicates.

Background

The paper discusses a possible dependence of planetary iron mass fraction on orbital period or equilibrium temperature. One proposed explanation is that iron could become relatively more abundant than silicates for planets located interior to the silicate sublimation line. However, the authors note that the feasibility of forming rocky planets at such close separations has not been established, leaving the relevant formation pathway unresolved.

References

One possibility is that iron becomes more abundant relative to silicates interior to the silicate sublimation line, though whether rocky planets can form at such close separations remains uncertain \citep{Chiang2013, Chatterjee2014, Owen2017}.

— No statistically significant evidence for a correlation between stellar and planetary composition  (2609.17159 - Turner et al., 15 Sep 2026) in Section 5.3, “Benchmarking to the Solar System”