10 September 2014 Siyi Xu ESO Fellow (Garching) Elemental Compositions of Extrasolar Planetesimals.
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Transcript of 10 September 2014 Siyi Xu ESO Fellow (Garching) Elemental Compositions of Extrasolar Planetesimals.
10 September 2014
Thanks to all my collaborators…
Michael Jura Ben Zuckerman Beth Klein Detlev Koester
(Poster DD-2)
(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
Evidence I: 25-50% WDs show heavy elements in the atmospheres.
There must be some external source constantly feeding the WDs!
Gaensicke, Koester+2012
High-resolution spectroscopic studies of heavy-element-enriched white dwarfs uniquely
measure the bulk compositions of extrasolar planetesimals.
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
Core/Crust
Differentiation and collision is common among extrasolar planetesimals
log n(Fe)/n(Si)
log
n(M
g)/
n(S
i)
Jura & Young 2014
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
• 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