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Observation of the ^(60)Fe nucleosynthesis-clock isotope in galactic cosmic rays

Binns, W. R. and Israel, M. H. and Christian, E. R. and Cummings, A. C. and de Nolfo, G. A. and Lave, K. A. and Leske, R. A. and Mewaldt, R. A. and Stone, E. C. and von Rosenvinge, T. T. and Wiedenbeck, M. E. (2016) Observation of the ^(60)Fe nucleosynthesis-clock isotope in galactic cosmic rays. Science, 352 (6286). pp. 677-680. ISSN 0036-8075. doi:10.1126/science.aad6004.

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^(60)Fe is a radioactive isotope in cosmic rays that serves as a clock to infer an upper limit on the time between nucleosynthesis and acceleration. We have used the ACE-CRIS instrument to collect 3.55 × 10^5 iron nuclei, with energies ~195 to ~500 MeV/nucleon, of which we identify 15 ^(60)Fe nuclei. The ^(60)Fe/^(56)Fe source ratio is (7.5 ± 2.9) × 10^(−5). The detection of supernova-produced ^(60)Fe in cosmic rays implies that the time required for acceleration and transport to Earth does not greatly exceed the ^(60)Fe half-life of 2.6 Myr and that the ^(60)Fe source distance does not greatly exceed the distance cosmic rays can diffuse over this time, ⪍ 1 kpc. A natural place for ^(60)Fe origin is in nearby clusters of massive stars.

Item Type:Article
Related URLs:
URLURL TypeDescription
Binns, W. R.0000-0001-6110-3407
Israel, M. H.0000-0002-8104-208X
Christian, E. R.0000-0003-2134-3937
Cummings, A. C.0000-0002-3840-7696
de Nolfo, G. A.0000-0002-3677-074X
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Wiedenbeck, M. E.0000-0002-2825-3128
Alternate Title:Observation of the 60Fe nucleosynthesis-clock isotope in galactic cosmic rays
Additional Information:© 2016 American Association for the Advancement of Science. Received 3 November 2015; accepted 18 March 2016. Published online 21 April 2016. This work was supported by NASA Grants NNX08Al11G and NNX13AH66G at the California Institute of Technology, the Jet Propulsion Laboratory, and Washington University in St. Louis. Goddard Space Flight Center was funded by NASA through the ACE Project. We thank S. Woosley and J. Brown at the University of California Santa Cruz for providing modeling calculation data and for discussions about uncertainties in their calculations. We thank A. Chieffi at the Institute for Space Astrophysics and Planetology, Rome, Italy, for discussions on the uncertainties in the C&L calculations. Accelerator testing of the CRIS detectors was made possible by N. Anantaraman, R. Ronningen, and the staff at the National Superconducting Cyclotron Laboratory at Michigan State University, while H. Specht, D. Schardt, and the staff of the GSI heavy ion accelerator in Darmstadt, Germany made possible the heavy ion calibrations of the completed CRIS instrument. The data used are archived at NASA's Space Physics Data Facility ( as dataset ac_h2_cris and can be retrieved from this site by direct download or through the SPDF’s CDAWeb data service.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Issue or Number:6286
Record Number:CaltechAUTHORS:20160422-072602817
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Official Citation:Observation of the 60Fe nucleosynthesis-clock isotope in galactic cosmic rays By W. R. Binns, M. H. Israel, E. R. Christian, A. C. Cummings, G. A. de Nolfo, K. A. Lave, R. A. Leske, R. A. Mewaldt, E. C. Stone, T. T. von Rosenvinge, M. E. Wiedenbeck Science 06 May 2016:Vol. 352, Issue 6286, pp. 677-680 DOI: 10.1126/science.aad6004
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66389
Deposited By: Tony Diaz
Deposited On:22 Apr 2016 15:17
Last Modified:10 Nov 2021 23:57

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