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| Titel |
Planetesimal Compositions in Exoplanet Systems based on Host Star Composition |
| VerfasserIn |
T. V. Johnson, O. Mousis, J. I. Lunine, N. Madhusudhan |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069099
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| Zusammenfassung |
| We have used recent surveys of the stellar abundances of solid forming elements in a sample
of exoplanet host stars discussed by Bond et al. (Astrophys. J. 715, 1050-1070, 2010) to
calculate the expected composition of silicate and ice planetesimals formed beyond the snow
line in these systems. The refractory silicate and metal composition is derived following
Johnson and Lunine (Nature 435, 69-71, 2005) and Wong et al. (in Oxygen in the Solar
System Vol. Reviews in Mineralogy and Geochemistry Vol. 68 (ed G. J. MacPherson) Ch. 10,
241-246, 2008). The nebula gas C and O composition was set based on amount of O tied up
in refractories and the volatile condensation sequence for ices in the 5-10 AU region
of the stellar systems calculated following Mousis et al. (Astrophys. J. 727, 7pp,
2011). The resultant condensate compositions show that planetesimal compositions
in exoplanet systems may differ significantly from solar system planet forming
materials.
The C/O abundance of the exoplanet host star has the strongest effect on planetesimal
composition, strongly affecting the relative proportions of refractory materials and volatile
ices, particularly water ice and C-bearing ices. For stars with sub-solar C/O values H2O and
silicate plus metal dominate the condensate composition with CO2 as the next most abundant
species at < ~0.10 mass fraction. Minor species (CH3OH, H2S, NH3, CH4, PH3), with
mass fractions of 10-4to 10-2, are present in approximately the relative proportions as for
the solar nebula. As stellar C/O increases, H2O decreases and beyond the solar value ([C/O]
=0, C/O = 0.55), rapidly disappears as the C/O = ~0.8 is approached, with CO2
and CH3OH ices becoming more important. Planetesimals in these systems will
have refractory, silicate plus metal rich compositions compared with solar system
conditions. If the midplane temperatures in the circumstellar nebula are |
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