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Centro de Astrofísica da Universidade do Porto

Low Mg/Si Planetary Host Stars and Their Mg-Depleted Terrestrial Planets

J. C. Carter-Bond, D. P. O'Brien, E. Delgado Mena, G. Israelian, N. C. Santos, J. I. González Hernández

Abstract
Simulations have shown that a diverse range of extrasolar terrestrial planet bulk compositions are likely to exist based on the observed variations in host star elemental abundances. Based on recent studies, it is expected that a significant proportion of host stars may have Mg/Si ratios below 1. Here we examine this previously neglected group of systems. Planets simulated as forming within these systems are found to be Mg-depleted (compared to Earth), consisting of silicate species such as pyroxene and various feldspars. Planetary carbon abundances also vary in accordance with the host star C/O ratio. The predicted abundances are in keeping with observations of polluted white dwarfs, lending validity to this approach. Further studies are required to determine the full planetary impacts of the bulk compositions predicted here.

Keywords
planetary systems – planets and satellites: composition – planets and satellites: formation

Notes
Note that this is the elemental ratio, not the solar-normalized logarithmic ratio, which is commonly shown as [X/H].

The Astrophysical Journal Letters
Volume 757, Page L2_1
March 2012

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