Publication Date:
2016-04-23
Description:
Iron-60 ((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 x 10(5) iron nuclei, with energies ~195 to ~500 mega-electron volts per nucleon, of which we identify 15 (60)Fe nuclei. The (60)Fe/(56)Fe source ratio is (7.5 +/- 2.9) x 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 million years and that the (60)Fe source distance does not greatly exceed the distance cosmic rays can diffuse over this time, 1 kiloparsec. A natural place for (60)Fe origin is in nearby clusters of massive stars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Binns, W R -- Israel, M H -- Christian, E R -- Cummings, A C -- de Nolfo, G A -- Lave, K A -- Leske, R A -- Mewaldt, R A -- Stone, E C -- von Rosenvinge, T T -- Wiedenbeck, M E -- New York, N.Y. -- Science. 2016 May 6;352(6286):677-80. doi: 10.1126/science.aad6004. Epub 2016 Apr 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Washington University, St. Louis, MO 63130, USA. wrb@wustl.edu mhi@wustl.edu. ; NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA. ; California Institute of Technology, Pasadena, CA 91125, USA. ; Washington University, St. Louis, MO 63130, USA. ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27103666" target="_blank"〉PubMed〈/a〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
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Chemistry and Pharmacology
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Computer Science
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Medicine
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Natural Sciences in General
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Physics
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