paper

C/O and Mg/Si Ratios of Stars in the Solar Neighborhood

arXiv:1608.06286 · doi:10.3847/1538-4357/aa6d53

Abstract

The carbon to oxygen ratio in a protoplanetary disk can have a dramatic influence on the compositions of any terrestrial planets formed. In regions of high C/O, planets form primarily from carbonates and in regions of low C/O, the ratio of magnesium to silicon determines the types of silicates which dominate the compositions. We present C/O and Mg/Si ratios for 849 F, G, and K dwarfs in the solar neighborhood. We find that the frequency of carbon-rich dwarfs in the solar neighborhood is < 0.13% and that 156 known planet hosts in the sample follow a similar distribution as all of the stars as a whole. The cosmic distribution of Mg/Si for these same stars is broader than the C/O distribution and peaks near 1.0 with % of systems having Mg/Si , leading to rocky planet compositions similar to the Earth. This leaves 40% of systems that can have planets that are silicate rich and may have very different compositions than our own.

9 pages, 5 figures, 1 ancillary data table. Accepted for publication to ApJ

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