The silicate and carbon-rich models of CoRoT-7b, Kepler-9d and Kepler-10b

Abstract

Possible bulk compositions of the super-Earth exoplanets, are investigated by applying a commonly used silicate and a non-standard carbon model. Their internal structures are deduced using the suitable equation of state of the materials. The degeneracy problems of their compositions can be partly overcome, based on the fact that all three planets are extremely close to their host stars. By analyzing the numerical results, we conclude: 1) The iron core of CoRoT-7b is not more than 27% of its total mass within 1 σ mass-radius error bars, so an Earth-like composition is less likely, but its carbon rich model can be compatible with an Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely with a Mercury-like composition, its old age implies that its high iron content may be a result of strong solar wind or giant impact; 3) the transiting-only superEarth Kepler-9d is also discussed. Combining its possible composition with the formation theory, we can place some constraints on its mass and bulk composition.

Zinc-blende to rocksalt transition in SiC in a laser-heated diamond-anvil cell

“…However, if SiC becomes ~17% more dense at 60 GPa, the expected density of a carbonrich planet will be greater than previously thought, nearly matching that of bridgmanite. We model the mass-radius (M-R) relation of a planet for different interior compositions based on the procedure in [29] considering several different scenarios. We recreate the massradius curve for SiC planets using the equation of state for the B3 structure, as used in [28][29][30] for possible carbon planet identification.…”

“…We model the mass-radius (M-R) relation of a planet for different interior compositions based on the procedure in [29] considering several different scenarios. We recreate the massradius curve for SiC planets using the equation of state for the B3 structure, as used in [28][29][30] for possible carbon planet identification. We also plot the mass-radius curve for a SiC planet using the B1 equation of state as determined in [31] for large carbon-rich bodies.…”

“…We also plot the mass-radius curve for a SiC planet using the B1 equation of state as determined in [31] for large carbon-rich bodies. For comparison, we also reproduce the mass-radius relation for MgSiO 3 bridgmanite, Fe and H 2 O ice [29,30] (Fig. 6).…”

Atmosphere-Interior Exchange on Hot, Rocky Exoplanets

“…Because atmospheric thickness and magmaplanet variability are potentially observable, this suggests a route to constrain hot-rocky-planet composition. Such routes are valuable, because mass and radius measurements only weakly constrain the composition of exoplanet silicates (Dorn et al 2015;Fogtmann-Schulz et al 2014;Gong & Zhou 2012;Rogers & Seager 2010).…”

SiO2‐SiC Mixtures at High Pressures and Temperatures: Implications for Planetary Bodies Containing SiC

“…Surface gravity (approximated as G*M/R where G is 6.67408e‐11 m 3 kg −1 s −2 , M is total mass and R is total radius) is calculated for an Earth‐mass planet composed of a SiC mantle and an Fe core. We consider a simple scenario in which Fe contributes 25% of the total density (i.e., the core) with the remainder Si and C and find the M‐R curve for such a planet based on the method in (Gong & Zhou, ). The terminal settling velocity is considered for diamond grains of 1 cm in diameter.…”