Element abundance patterns in stars indicate fission of nuclei heavier than uranium

Ian U Roederer; Nicole Vassh; Erika M Holmbeck; Matthew R Mumpower; Rebecca Surman; John J Cowan; Timothy C Beers; Rana Ezzeddine; Anna Frebel; Terese T Hansen; Vinicius M Placco; Charli M Sakari

doi:10.1126/science.adf1341

Element abundance patterns in stars indicate fission of nuclei heavier than uranium

Science. 2023 Dec 8;382(6675):1177-1180. doi: 10.1126/science.adf1341. Epub 2023 Dec 7.

Authors

Ian U Roederer¹, Nicole Vassh², Erika M Holmbeck³, Matthew R Mumpower^{4

5}, Rebecca Surman⁶, John J Cowan⁷, Timothy C Beers⁶, Rana Ezzeddine⁸, Anna Frebel^{9

10}, Terese T Hansen¹¹, Vinicius M Placco¹², Charli M Sakari¹³

Affiliations

¹ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA.
² TRIUMF (Tri-University Meson Facility), Vancouver, BC V6T 2A3, Canada.
³ Carnegie Observatories, Pasadena, CA 91101, USA.
⁴ Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
⁵ Center for Theoretical Astrophysics, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
⁶ Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN 46556, USA.
⁷ Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA.
⁸ Department of Astronomy, University of Florida, Bryant Space Science Center, Gainesville, FL 32611, USA.
⁹ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
¹⁰ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
¹¹ Department of Astronomy, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden.
¹² National Optical-Infrared Astronomy Research Laboratory, National Science Foundation, Tucson, AZ 85719, USA.
¹³ Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132, USA.

PMID: 38060658
DOI: 10.1126/science.adf1341

Abstract

The heaviest chemical elements are naturally produced by the rapid neutron-capture process (r-process) during neutron star mergers or supernovae. The r-process production of elements heavier than uranium (transuranic nuclei) is poorly understood and inaccessible to experiments so must be extrapolated by using nucleosynthesis models. We examined element abundances in a sample of stars that are enhanced in r-process elements. The abundances of elements ruthenium, rhodium, palladium, and silver (atomic numbers Z = 44 to 47; mass numbers A = 99 to 110) correlate with those of heavier elements (63 ≤ Z ≤ 78, A > 150). There is no correlation for neighboring elements (34 ≤ Z ≤ 42 and 48 ≤ Z ≤ 62). We interpret this as evidence that fission fragments of transuranic nuclei contribute to the abundances. Our results indicate that neutron-rich nuclei with mass numbers >260 are produced in r-process events.