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<p>Where are the heavy elements produced in the Universe? While core-collapse supernovae are confirmed sources of <sup>60</sup>Fe, the origin of heavier r-process nuclei such as <sup>244</sup>Pu and <sup>247</sup>Cm remains debated. Here we used single-atom counting of live <sup>60</sup>Fe, <sup>244</sup>Pu and <sup>247</sup>Cm in a deep-ocean ferromanganese crust to trace such nucleosynthesis events near Earth over millions of years. The observed non-correlation of the <sup>244</sup>Pu and <sup>60</sup>Fe profiles supports a continuous r-process influx to Earth that is independent of core-collapse supernovae and constrains the core-collapse supernova r-process yield of actinide isotopes. The non-observation of <sup>247</sup>Cm, produced concurrently with <sup>244</sup>Pu, sets a time limit on the last actinide-producing r-process event near Earth of more than 90–100 Myr ago. Our measured interstellar signatures suggest the occurrence of an old and rare r-process event leading to a diffuse <sup>244</sup>Pu background inside and outside the Local Bubble.</p>

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The timing of the last r-process event near Earth from interstellar 60Fe, 244Pu and 247Cm deposition on Earth

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月15日

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  • Dominik Koll,
  • Sebastian Fichter,
  • Michael A. C. Hotchkis,
  • Stephen T. Battisson,
  • Sabrina Beutner,
  • L. Keith Fifield,
  • Michaela B. Froehlich,
  • Johannes Lachner,
  • Stefan Pavetich,
  • Georg Rugel,
  • Zuzana Slavkovská,
  • Stephen G. Tims,
  • Anton Wallner

摘要

Where are the heavy elements produced in the Universe? While core-collapse supernovae are confirmed sources of 60Fe, the origin of heavier r-process nuclei such as 244Pu and 247Cm remains debated. Here we used single-atom counting of live 60Fe, 244Pu and 247Cm in a deep-ocean ferromanganese crust to trace such nucleosynthesis events near Earth over millions of years. The observed non-correlation of the 244Pu and 60Fe profiles supports a continuous r-process influx to Earth that is independent of core-collapse supernovae and constrains the core-collapse supernova r-process yield of actinide isotopes. The non-observation of 247Cm, produced concurrently with 244Pu, sets a time limit on the last actinide-producing r-process event near Earth of more than 90–100 Myr ago. Our measured interstellar signatures suggest the occurrence of an old and rare r-process event leading to a diffuse 244Pu background inside and outside the Local Bubble.