Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published September 10, 2010 | Published
Journal Article Open

Neutron-rich Chromium Isotope Anomalies in Supernova Nanoparticles


Neutron-rich isotopes with masses near that of iron are produced in Type Ia and II supernovae (SNeIa and SNeII). Traces of such nucleosynthesis are found in primitive meteorites in the form of variations in the isotopic abundance of ^(54)Cr, the most neutron-rich stable isotope of chromium. The hosts of these isotopic anomalies must be presolar grains that condensed in the outflows of SNe, offering the opportunity to study the nucleosynthesis of iron-peak nuclei in ways that complement spectroscopic observations and can inform models of stellar evolution. However, despite almost two decades of extensive search, the carrier of ^(54)Cr anomalies is still unknown, presumably because it is fine grained and is chemically labile. Here, we identify in the primitive meteorite Orgueil the carrier of ^(54)Cr anomalies as nanoparticles (<100 nm), most likely spinels that show large enrichments in ^(54)Cr relative to solar composition ((54)^Cr/^(52)Cr ratio >3.6 × solar). Such large enrichments in ^(54)Cr can only be produced in SNe. The mineralogy of the grains supports condensation in the O/Ne-O/C zones of an SNII, although a Type Ia origin cannot be excluded. We suggest that planetary materials incorporated different amounts of these nanoparticles, possibly due to late injection by a nearby SN that also delivered ^(26)Al and ^(60)Fe to the solar system. This idea explains why the relative abundance of ^(54)Cr and other neutron-rich isotopes vary between planets and meteorites. We anticipate that future isotopic studies of the grains identified here will shed new light on the birth of the solar system and the conditions in SNe.

Additional Information

© 2010. The American Astronomical Society. All rights reserved. Received 2010 May 13; accepted 2010 July 5; published 2010 August 23. Discussions with B.S. Meyer, F.K. Thielemann, T. Rauscher, R. Yokochi, A.M. Davis, and P.R. Craddock were appreciated. We thank T. Stephan and F.J. Stadermann for their help in our attempt to acquire Auger data on the 54Cr-rich grains. Constructive comments from an anonymous referee greatly improved the manuscript. The TEM national facility in Lille (France) is supported by the Conseil Regional du Nord-Pas de Calais, the European Regional Development Fund (ERDF), and the Institut National des Sciences de l'Univers (INSU, CNRS). J.H.C. and the laboratories at JPL were supported by NASA Cosmochemistry. This work was supported by a Packard fellowship, the France Chicago Center, a Moore Distinguished Scholarship at the California Institute of Technology, and NASA and NSF through grants NNX09AG59G and EAR-0820807 to N.D.

Attached Files

Published - Dauphas2010p11438Astrophys_J.pdf


Files (2.5 MB)
Name Size Download all
2.5 MB Preview Download

Additional details

August 22, 2023
October 20, 2023