Supernovae and r-process – the extraordinary development of AMS for identifying traces of interstellar origin
1Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
The solar system moves through the Interstellar Medium (ISM) and collects interstellar dust particles that contain signatures of ongoing nucleosynthesis processes but also of rare cosmic explosions. Isotopic fingerprints of such cosmic events include longer-lived radionuclides that can be measured with high sensitivity via AMS before they decay away. The most prominent examples are 60Fe (t1/2=2.6 Myr) and 244Pu (81 Myr) but also other candidates such as 53Mn, 26Al or 182Hf.
Since more than 5 decades a number of extraterrestrial radionuclides had been detected, e.g. in lunar samples or meteorites. However, only with the advent of AMS and with a dedicated approach starting ~25 years ago, searches in deep-sea archives succeeded in identifying traces of live radionuclides from extra-solar, i.e. interstellar sources.
Today, AMS measurements of 60Fe from various archives have demonstrated a clear exposure of Earth to recent (<10 Myr) supernova explosions. In addition, the recent finding of ISM-244Pu, exclusively produced by the r-process, allows to link supernovae and r-process signatures. This latter process requires an explosive scenario but is far from being fully understood; in particular, its sites and history remain heavily debated.
In this presentation, I will summarize the challenge and the immense progress in detection efficiency and sensitivity for these nuclides. It will also highlight the different fate of 60Fe- and 244Pu-AMS since their inception.