1. 10 September 2014 Siyi Xu ESO Fellow (Garching) Elemental Compositions of Extrasolar Planetesimals

2. 10 September 2014 Thanks to all my collaborators… Michael JuraBen Zuckerman Beth KleinDetlev Koester (Poster DD-2)

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

5. Wesemael+1993 Typical white dwarf spectra:

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

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 Xu+ 2013 PG 1225-079

11. Planetesimals Accreted onto WDs: mass 10 18 -10 23 g 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. Core/Crust Differentiation and collision is common among extrasolar planetesimals log n(Fe)/n(Si) log n(Mg)/n(Si) Jura & Young 2014

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

15. 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! Summary sxu@eso.org

16. Back Up Slides

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