[Research Article] Observation of the 60Fe nucleosynthesis-clock isotope in galactic cosmic rays

Thursday, May 5, 2016 - 14:01 in Astronomy & Space

Iron-60 (60Fe) 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 × 105 iron nuclei, with energies ~195 to ~500 mega–electron volts per nucleon, of which we identify 15 60Fe nuclei. The 60Fe/56Fe source ratio is (7.5 ± 2.9) × 10−5. The detection of supernova-produced 60Fe in cosmic rays implies that the time required for acceleration and transport to Earth does not greatly exceed the 60Fe half-life of 2.6 million years and that the 60Fe source distance does not greatly exceed the distance cosmic rays can diffuse over this time, ⪍1 kiloparsec. A natural place for 60Fe origin is in nearby clusters of massive stars. Authors: W. R. Binns, M. H. Israel, E. R. Christian, A. C. Cummings, G. A. de Nolfo, K. A. Lave, R. A....

Read the whole article on Science NOW

More from Science NOW

Latest Science Newsletter

Get the latest and most popular science news articles of the week in your Inbox! It's free!

Check out our next project, Biology.Net