Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022
EPSC Abstracts
Vol. 16, EPSC2022-188, 2022
https://doi.org/10.5194/epsc2022-188
Europlanet Science Congress 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

The effect of stellar composition on nebular condensation

Paolo Sossi1 and Haiyang Wang2
Paolo Sossi and Haiyang Wang
  • 1ETH Zurich, Institute of Geochemistry and Petrology, Zurich, Switzerland (paolo.sossi@erdw.ethz.ch)
  • 2ETH Zurich, Institute for Particle Physics and Astrophysics, Zurich, Switzerland (haiwang@phys.ethz.ch)

The volatility of an element is defined by its 50% condensation temperature (Tc50) from a nebular gas of Solar composition at 10-4 bar. However, the variability in compositions of extrasolar systems inferred from the spectroscopic measurements of their parent stars implies that the identity, abundance and sequence of condensing phases should deviate from that of our Solar System. Here we perform Gibbs free energy minimisation with FactSage over temperatures from 1723 K to 473 K and 10-4 bar total pressure to calculate the condensation sequence of 39 stellar compositions in the system H-C-O-Na-Mg-Al-Si-S-Ca-Ti-Fe-Ni that span the range from -0.4 to +0.4 dex. In accord with previous work, the C/O ratio of the gas plays a profound role in determining the mineralogy and order of condensing phases. Nebulae with 0.3 < C/O < 0.75 display broadly solar condensation sequences. Condensing nebulae with C/O > 0.75 exhibit strongly decreasing Tc50 of lithophile elements whose condensation reactions depend upon the availability of oxygen (Ca, Al, Si, Ti, Mg) relative to those whose condensation does not (Fe, Ni). This trend is progressively reversed at very high C/O ratios for elements that form stable carbides, namely, TiC (C/O > 0.9) and SiC (C/O > 0.95), causing a dramatic increase in the Tc50 of Ti and Si. The Tc50 of S jumps from ~650 K below C/O = 0.75 to ~1100 K above C/O = 0.75 due to the condensation of oldhamite (CaS) and plateaus at higher C/O. The Tc50 of Fe and Ni increase monotonically with Fe/H, and are fit to equations Tc50(Fe) = 87.3(Fe/H) + 682 (r2 = 0.999) and Tc50(Ni) = 88.7(Fe/H) + 696 (r2 = 0.999) valid for 7.08 < Fe/H < 7.95 and 0.3 < C/O < 0.95. As the C/O and Fe/H ratios are broadly correlated, only high metallicity stars are expected to produce nebula condensates whose compositions diverge drastically from those of our Solar System. Planets formed from these systems should be richer in Fe, Ni and S at the expense of Al and Ca.

How to cite: Sossi, P. and Wang, H.: The effect of stellar composition on nebular condensation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-188, https://doi.org/10.5194/epsc2022-188, 2022.

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