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Published byLeon Matthews Modified over 9 years ago
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10 September 2014 Siyi Xu ESO Fellow (Garching) Elemental Compositions of Extrasolar Planetesimals
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10 September 2014 Thanks to all my collaborators… Michael JuraBen Zuckerman Beth KleinDetlev Koester (Poster DD-2)
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(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
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Wesemael+1993 Typical white dwarf spectra:
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Evidence I: 25-50% WDs show heavy elements in the atmospheres. There must be some external source constantly feeding the WDs! Gaensicke, Koester+2012
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Evidence II: ~4% single WDs show infrared excess from an orbiting dust disk.
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High-resolution spectroscopic studies of heavy-element-enriched white dwarfs uniquely measure the bulk compositions of extrasolar planetesimals.
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Keck/HIRES Spectra Xu+ 2014
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HST/COS Spectra Xu+ 2013 PG 1225-079
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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
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The compositions of extrasolar planetesimals resemble bulk earth. Xu+ 2014
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Core/Crust Differentiation and collision is common among extrasolar planetesimals log n(Fe)/n(Si) log n(Mg)/n(Si) Jura & Young 2014
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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
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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
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Back Up Slides
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GD 362: the best match solar system analog is mesosiderite Condensation Temperature volatilerefractory
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