J/ApJ/733/L31 Distribution of 26Al in the solar system (Makide+, 2011)
Heterogeneous distribution of 26Al at the birth of the solar system.
Makide K., Nagashima K., Krot A.N., Huss G.R., Ciesla F.J., Hellebrand E.,
Gaidos E., Yang L.
<Astrophys. J., 733, L31 (2011)>
=2011ApJ...733L..31M 2011ApJ...733L..31M
ADC_Keywords: Solar system ; Atomic physics ; Comets
Keywords: meteorites, meteors, meteoroids - protoplanetary disks -
stars: Wolf-Rayet - Sun: evolution - supernovae: general
Abstract:
It is believed that 26Al, a short-lived (t1/2=0.73Ma) and now
extinct radionuclide, was uniformly distributed in the nascent solar
system (SS) with the initial 26Al/27Al ratio of ∼5.2x10-5,
suggesting an external, stellar origin rather than local, solar
source. However, the stellar source of 26Al and the manner in which
it was injected into the SS remain controversial: the 26Al could
have been produced by an asymptotic giant branch star, a supernova, or
a Wolf-Rayet star and injected either into the protosolar molecular
cloud, protosolar cloud core, or protoplanetary disk. Corundum
(Al2O3) is predicted to be the first condensate from a cooling gas
of solar composition. Here we show that micron-sized corundum
condensates from 16O-rich (Δ17O~-25%) gas of solar
composition recorded heterogeneous distribution of 26Al at the birth
of the SS: the inferred initial 26Al/27Al ratio ranges from
∼6.5x10-5 to <2x10-6; 52% of corundum grains measured are
26Al-poor. Abundant 26Al-poor, 16O-rich refractory objects
include grossite- and hibonite-rich calcium-aluminum-rich inclusions
(CAIs) in CH (high metal abundance and high iron concentration)
chondrites, platy hibonite crystals in CM (Mighei-like) chondrites,
and CAIs with fractionation and unidentified nuclear effects CAIs
chondrites. Considering the apparently early and short duration
(<0.3Ma) of condensation of refractory 16O-rich solids in the SS, we
infer that 26Al was injected into the collapsing protosolar
molecular cloud and later homogenized in the protoplanetary disk. The
apparent lack of correlation between 26Al abundance and O-isotope
composition of corundum grains constrains the stellar source of 26Al
in the SS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 86 116 Oxygen-isotope compositions and the inferred
(26Al/27Al)0 ratios from individual
micron-sized corundum grain in unequilibrated
ordinary chondrites (UOCs) and unmetamorphosed
CM carbonaceous chondrites (CCs)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Type chondrite type (Carbonaceus or Ordinary)
25- 38 A14 --- Grain Grain (1)
40- 44 F5.1 10-3 d18O Excess δ18O of 18O isotope
46- 48 F3.1 10-3 e_d18O The 2σ error in d180
50- 54 F5.1 10-3 d17O Excess δ18O of 17O isotope
56- 59 F4.1 10-3 e_d17O The 2σ error in d170
61- 65 F5.1 10-3 D17O Δ17O composition (D17O=d17O-0.52*d18O)
67- 70 F4.1 10-3 e_D17O The 2σ error in D17O
72- 77 F6.3 10-5 Al.r ? Inferred (26Al/27Al)0 ratio (2)
79- 80 A2 --- f_Al.r [ND] ND: indicates Al.r not determined (2)
82- 86 F5.3 10-5 e_Al.r ? The 2σ error in Al.r
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Note (1): Abbreviations are:
Sem = Semarkona (LL3.0 UOC [unequilibrated ordinary chondrite])
Bis = Bishunpur (LL3.15 UOC [unequilibrated ordinary chondrite])
RC = Roosevelt County 075 (H3.10 UOC [unequilibrated ordinary chondrite])
ALHA = Alan Hills A77307 (CO3.0 CC [unmetamorphosed carbonaceous chondrite])
Mur = Murray (CM2 CC [unmetamorphosed carbonaceous chondrite])
Org = Orgueil (CI1 CC [unmetamorphosed carbonaceous chondrite])
Ren = Renazzo (CR2 CC [unmetamorphosed carbonaceous chondrite])
*P = presolar corundum grains;
*U = isotopically unusual corundum grains, possibly an analytical artifact.
"^" = grains with O-isotope compositions previously reported by
Makide et al. (2009GeCoA..73.5018M 2009GeCoA..73.5018M).
The *P and *U grains are not plotted in Figure 1 and not discussed in
the text.
Note (2): 26Al/27Al ratio could not be determined due to either the
presence of Mg-rich grains attached to corundum grains, or loss of
grains during oxygen isotopic measurements.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 19-Nov-2012