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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