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Title: HETEROGENEOUS DISTRIBUTION OF {sup 26}Al AT THE BIRTH OF THE SOLAR SYSTEM

It is believed that {sup 26}Al, a short-lived (t{sub 1/2} = 0.73 Ma) and now extinct radionuclide, was uniformly distributed in the nascent solar system (SS) with the initial {sup 26}Al/{sup 27}Al ratio of {approx}5.2 x 10{sup -5}, suggesting an external, stellar origin rather than local, solar source. However, the stellar source of {sup 26}Al and the manner in which it was injected into the SS remain controversial: the {sup 26}Al 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 (Al{sub 2}O{sub 3}) is predicted to be the first condensate from a cooling gas of solar composition. Here we show that micron-sized corundum condensates from {sup 16}O-rich ({Delta}{sup 17}O {approx} -25 per mille ) gas of solar composition recorded heterogeneous distribution of {sup 26}Al at the birth of the SS: the inferred initial {sup 26}Al/{sup 27}Al ratio ranges from {approx}6.5x10{sup -5} to <2x10{sup -6}; 52% of corundum grains measured are {sup 26}Al-poor. Abundant {sup 26}Al-poor, {sup 16}O-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 more » crystals in CM (Mighei-like) chondrites, and CAIs with fractionation and unidentified nuclear effects CAIs chondrites. Considering the apparently early and short duration (<0.3 Ma) of condensation of refractory {sup 16}O-rich solids in the SS, we infer that {sup 26}Al was injected into the collapsing protosolar molecular cloud and later homogenized in the protoplanetary disk. The apparent lack of correlation between {sup 26}Al abundance and O-isotope composition of corundum grains constrains the stellar source of {sup 26}Al in the SS. « less
Authors:
; ; ;  [1] ; ;  [2] ; ;  [3]
  1. Hawai'i Institute of Geophysics and Planetology, School of Ocean, Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)
  2. Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States)
  3. Department of Geology and Geophysics, University of Hawai'i at Manoa, Honolulu, HI 96822 (United States)
Publication Date:
OSTI Identifier:
21562641
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 733; Journal Issue: 2; Other Information: DOI: 10.1088/2041-8205/733/2/L31
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALUMINIUM 26; DISTRIBUTION; SOLAR SYSTEM ALUMINIUM ISOTOPES; BETA DECAY RADIOISOTOPES; BETA-PLUS DECAY RADIOISOTOPES; ISOTOPES; LIGHT NUCLEI; NUCLEI; ODD-ODD NUCLEI; RADIOISOTOPES; SECONDS LIVING RADIOISOTOPES; YEARS LIVING RADIOISOTOPES