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Elemental Compositions of Extrasolar Planetesimals

Elemental Compositions of Extrasolar Planetesimals. Siyi Xu ESO Fellow (Garching). Thanks to all my collaborators…. Beth Klein. Detlev Koester (Poster DD-2). Michael Jura. Ben Zuckerman. Earth as we know…. (i) Nebular Condensation * 94% O, Fe, Si, Mg * 0.17-0.39% C.

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Elemental Compositions of Extrasolar Planetesimals

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  1. Elemental Compositions of Extrasolar Planetesimals Siyi Xu ESO Fellow (Garching)

  2. Thanks to all my collaborators… Beth Klein Detlev Koester (Poster DD-2) Michael Jura Ben Zuckerman

  3. Earth as we know… (i) Nebular Condensation * 94% O, Fe, Si, Mg * 0.17-0.39% C (ii) Differentiation Mg Fe Si, Mg Is Earth normal?

  4. Main Story: Some white dwarfs are accreting their own planetesimals and display their compositions in the atmospheres.

  5. Typical white dwarf spectra: Wesemael+1993

  6. Evidence I: 25-50% WDs show heavy elements in the atmospheres. Gaensicke, Koester+2012 There must be some external source constantly feeding the WDs!

  7. Evidence II: ~4% single WDs show infrared excess from an orbiting dust disk.

  8. High-resolution spectroscopic studies of heavy-element-enriched white dwarfs uniquely measure the bulk compositions of extrasolar planetesimals.

  9. Keck/HIRES Spectra Xu+ 2014

  10. HST/COS Spectra PG 1225-079 Xu+ 2013

  11. Planetesimals Accreted onto WDs: • mass 1018-1023g • 19 heavy elements detected C, S, O, Na, Cu, Mn, P, Cr, Si, Mg, Fe, Co, Ni, V, Sr, Ca, Ti, Al, Sc

  12. The compositions of extrasolar planetesimals resemble bulk earth. Xu+ 2014

  13. Differentiation and collision is common among extrasolar planetesimals log n(Mg)/n(Si) Jura & Young 2014 log n(Fe)/n(Si) Core/Crust

  14. A pilot search for extrasolar plate tectonics • Earth’s continental crust is enriched in incompatible elements, e.g. Ba, Sr.. less than 1% material is from continental crust GD 362 Jura+ 2014

  15. Summary • Heavy-element-enriched WDs are a powerful tool to study compositions of extrasolar planetesimals • Extrasolar planetesimals resemble bulk Earth • Dominated by O ,Mg, Si, Fe, very little C • Differentiation and collision is widespread Thank you! sxu@eso.org

  16. Back Up Slides

  17. GD 362: the best match solar system analog is mesosiderite volatile refractory Condensation Temperature

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