Settling the Half-Life of ⁶⁰Fe: Fundamental for a Versatile Astrophysical Chronometer

Abstract

In order to resolve a recent discrepancy in the half-life of 60Fe, we performed an independent measurement with a new method that determines the 60Fe content of a material relative to 55Fe(t1/2 = 2.744 yr) with accelerator mass spectrometry. Our result of (2.50 +/- 0.12) × 106 yr clearly favors the recently reported value (2.62 +/- 0.04) × 106 yr, and rules out the older result of (1.49 +/- 0.27) × 106 yr. The present weighted mean half-life value of (2.60 +/- 0.05) × 106 yr substantially improves the reliability as an important chronometer for astrophysical applications in the million-year time range. This includes its use as a sensitive probe for studying recent chemical evolution of our Galaxy, the formation of the early Solar System, nucleosynthesis processes in massive stars, and as an indicator of a recent nearby supernova.