elemental compositions of extrasolar planetesimals
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
10 September 2014
Siyi XuESO 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
Wesemael+1993
Typical white dwarf spectra:
Evidence I: 25-50% WDs show heavy elements in the atmospheres.
There must be some external source constantly feeding the WDs!
Gaensicke, Koester+2012
Evidence II: ~4% single WDs show infrared excess from an orbiting dust disk.
High-resolution spectroscopic studies of heavy-element-enriched white dwarfs uniquely
measure the bulk compositions of extrasolar planetesimals.
Keck/HIRES Spectra
Xu+ 2014
HST/COS Spectra
Xu+ 2013
PG 1225-079
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
The compositions of extrasolar planetesimals resemble bulk earth.
Xu+ 2014
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
Back Up Slides
GD 362: the best match solar system analog is mesosiderite
Condensation Temperature
volatile refractory