Jorge, David

Kamp, Inga

Spaargaren, Rob

Waters, Rens

Woitke, Peter

English

We aim to understand the impact of different refractory element ratios such as Mg, Si, and Fe on the composition of planets. We use the thermodynamic equilibrium code GGchem to simulate the condensation of solids in a minimum mass solar nebula around main sequence G-type stars within 150pc. We extract the stellar elemental composition from the Hypatia database. We find that a lower Mg/Si ratio shifts the condensation sequence from forsterite and SiO to enstatite and quartz; a lower Fe/S ratio leads to the formation of FeS and FeS2 and little or no Fe-bearing silicates. Ratios of refractory elements translate directly from the gas phase to the condensed phase for 

ARTS repository - University of Groningen

   University of GroningenForming planets around stars with non-solar compositionJorge, David; Kamp, Inga; Waters, Rens; Woitke, Peter; Spaargaren, RobIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2021Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Jorge, D., Kamp, I., Waters, R., Woitke, P., & Spaargaren, R. (2021). Forming planets around stars withnon-solar composition. EPSC2021-853. Abstract from Europlanet Science Congress 2021.https://ui.adsabs.harvard.edu/abs/2021EPSC...15..853JCopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 07-06-2022EPSC AbstractsVol. 15, EPSC2021-853, 2021, updated on 03 Feb 2022https://doi.org/10.5194/epsc2021-853Europlanet Science Congress 2021© Author(s) 2022. This work is distributed underthe Creative Commons Attribution 4.0 License.Forming planets around stars with non-solar compositionDavid Jorge1, Inga Kamp1, Rens Waters2,3, Peter Woitke4, and Rob Spaargaren51Kapteyn Astronomical Institute, University of Groningen, The Netherlands2Radboud University Nijmegen, The Netherlands3SRON, The Netherlands4SUPA, University of St Andrews, UK5ETH Zurich, SwitzerlandAbstractWe aim to understand the impact of different refractory element ratios such as Mg, Si, and Fe on thecomposition of planets. We use the thermodynamic equilibrium code GGchem to simulate thecondensation of solids in a minimum mass solar nebula around main sequence G-type stars within150pc. We extract the stellar elemental composition from the Hypatia database. We find that alower Mg/Si ratio shifts the condensation sequence from forsterite and SiO to enstatite and quartz; alower Fe/S ratio leads to the formation of FeS and FeS2 and little or no Fe-bearing silicates. Ratios ofrefractory elements translate directly from the gas phase to the condensed phase for T<1000K.However, ratios with respect to volatile elements (e.g. oxygen and sulphur) in the condensates – thebuilding blocks of planets – differ from the original stellar composition. Our results can haveimportant implications for planet interiors, which depend strongly on the degree of oxidization andthe sulphur abundance.1. IntroductionPlanets form from solid material residing in the disk around a young star. Both the star and the diskare composed oft he same material (inherited from the collapsing cloud). In the inner disk (inside afew au), material is likely sublimating and solidifying repeatedly due to episodic accretion events andstellar luminosity peaks. Small variations from solar abundances (within 0.5dex), especially also forrefractory elements, are ubiqutous in the solar neighborhood. The question is whether such smallelement abundance fluctuations have a noticeable impact on the composition of a planet condensingfrom the planet forming disk.2. MethodsWe selected from the Hypatia Database [4] single solar-type main-sequence stars within 150 pc. Weselect stars that have as complete as possible chemical abundance data and draw six sample stars,representative of the typical spreads in the elements ratios (see Fig. 1).Figure 1: Ratios of the refractory elements Mg, Si and Fe, as well as S, for main-sequence G-typestars within 150pc. Black dots represent the location of the six sample stars. A red dot indicates astar for which we inferred missing abundances from the median of the known abundances. We use the GGchem code developed by [2] and re-written and updated by [6]. The thermo-chemicaldata are taken from the NIST-JANAF and the geophysical SUPCRTBL databases. The code has beensuccessfully benchmarked against the public TEA code [1]. Given a specific temperature andpressure, the code calculates the various molecules and condensates forming by minimizing theGibbs free energy. We choose 24 elements (H, He, Li, C, N, O, Na, Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr,Mn, Fe, Ni, Zr, W, F, P), leading to 552 molecules and 241 condensates. We use the pT-profile of theMinimum Mass Solar Nebula from [3] and assume that different parts of the disk do not mix andthat planets are forming in situ. We sample the results of the condensation sequences by defining locations for the formation ofhypothetical planets. Besides the current locations of Mercury, Venus, Earth, Mars, and the Asteroidbelt in the Solar system, we also use 1000, 1250 and 1500K, mimicking that solar system planetslikely formed at higher temperatures (dynamical evolution).Figure 2: Condensation sequence for Mg-bearing species for the solar abundances and two extremecases of Mg/Si ratio. Figure 3: The element ratios in the condensed phase from which the hypothetical planets form(noted in legend by their respective temperatures). Ratios are normalised to the Solar values. The x-axis label represents the solar composition (0) and the six sample stars. The black horizontal linerepresents the initial value of the gas phase ratio.3. Condensation sequencesFigure 2 shows the condensates containing magnesium for our six sample stars as a function oftemperature. Iron condenses as metallic Fe at very high temperature, removing it from the gasphase. For solar abundances of Mg and Si, forsterite and enstatite are both abundant down to~400K. Below that, they start to combine with hydrogen and form more complex silicates. Thisbehavior is highly dependent on the initial Mg/Si ratio. At a high Mg/Si ratio of 0.17dex, forsteritestays the most abundant condensate down to 240K; enstatite, quartz and SiO are absent. For a lowMg/Si ratio of -0.26dex, the high temperature condensates are SiO and forsterite; below ~1250K,we find instead SiO2 and enstatite. For Fe/S≥-0.25dex, iron forms at low temperatures various typesof Fe-bearing silicates while for Fe/S≤-0.67dex, Fe only forms FeS and FeS2.4. Planet compositionFigure 3 shows that the refractory elements are directly inherited from the gas phase. This is nottrue for more volatile species such as sulphur and oxygen. Planets forming from condensates attemperatures ³1000K do not show much S, because the lowest temperature condensate FeS formsat ~700K. Planets form at ³250K, inside the snow line, in an environment where a fraction of theoxygen remains in the gas phase, leading to condensates with higher refractory/oxygen ratios.Planets forming outside the snow line can obtain ratios equal to the initial gas phase.5. ConclusionsOur results show that planets could have more reduced interiors and an Fe/S ratio different from theinitial gas phase. This can alter the planets interior structure [5]. In conclusion, we show that thetypical spread (0.1-0.2dex) in the abundance of refractory elements in the Solar neighbourhooddoes impact significantly the outcome of planet formation.AcknowledgementsThis research was supported and inspired by discussions through the ISSI International Teamcollaboration "Zooming In On Rocky Planet Formation" (team 482).References[1] Blecic, J., Harrington, J., Bowman, M.O. 2016, ApJS, 225, 4[2] Gail, H.P., Sedlmayr, E. 1986, A&A, 166, 225[3] Hayashi, C. 1981, in IAUS, Vol. 93, ed. D. Sugimoto, D.Q. Lamb, D.N. Schramm, 113–126[4] Hinkel, N.R., Young, P.A., Pagano, M.D., et al. 2016, ApJS, 226, 4[5] Hirose, K., Labrosse, S., Hernlund, J. 2013, Annual Review of Earth and Planetary Sciences, 41,657[6] Woitke, P., Helling, C., Hunter, G.H., et al. 2018, A&A, 614, A1Powered by TCPDF (www.tcpdf.org)

Forming planets around stars with non-solar composition

https://pure.rug.nl/ws/files/202098561/EPSC2021_853_print.pdf

Forming planets around stars with non-solar composition

Abstract

Similar works

Full text

Available Versions

ARTS repository - University of Groningen