¹Maria Lugaro, ^1,2,3 Alexander Heger, ¹ Dean Osrin, ⁴ Stephane Goriely,⁵ Kai Zuber, ^6,7 Amanda I. Karakas, ^8,8,10 Brad K. Gibson, ¹ Carolyn L. Doherty, ¹ John C. Lattanzio, ¹¹ Ulrich Ott

¹Monash Centre for Astrophysics (MoCA), Monash University, Clayton VIC 3800, Australia.
²Joint Institute for Nuclear Astrophysics (JINA), 225 Nieuwland Science Hall, Department of Physics, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
³School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
⁴Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, CP-226, 1050, Brussels, Belgium.
⁵Institut für Kern- und Teilchenphysik, Technische Universität Dresden, 01069 Dresden, Germany.
⁶Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia.
⁷Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, the University of Tokyo, Japan.
⁸Jeremiah Horrocks Institute, University of Central Lancashire, Preston, PR1 2HE, UK.
⁹Institute for Computational Astrophysics, Department of Astronomy and Physics, Saint Mary’s University, Halifax, NS, BH3 3C3, Canada.
¹⁰UK Network for Bridging Disciplines of Galactic Chemical Evolution (BRIDGCE), http://www.astro.keele.ac.uk/bridgce, UK.
¹¹Faculty of Natural Science, University of West Hungary, 9700 Szombathely, Hungary.

Among the short-lived radioactive nuclei inferred to be present in the early solar system via meteoritic analyses, there are several heavier than iron whose stellar origin has been poorly understood. In particular, the abundances inferred for 182Hf (half-life = 8.9 million years) and 129I (half-life = 15.7 million years) are in disagreement with each other if both nuclei are produced by the rapid neutron-capture process. Here, we demonstrate that contrary to previous assumption, the slow neutron-capture process in asymptotic giant branch stars produces 182Hf. This has allowed us to date the last rapid and slow neutron-capture events that contaminated the solar system material at ∼100 million years and ∼30 million years, respectively, before the formation of the Sun.

Reference
Lugaro M, Heger A, Osrin D, Goriely S, Zuber K, Karakas AI, Gibson BK, Doherty CL, Lattanzio JC, Ott U (2014) Stellar origin of the 182Hf cosmochronometer and the presolar history of solar system matter. Science 345:6197, 650-653.
Link to Article [DOI: 10.1126/science.1253338]

Reprinted with permission from AAAS