We have made a new determination of the half-life of the radioactive isotope ${}^{60}\mathrm{Fe}$ using high precision measurements of the number of ${}^{60}\mathrm{Fe}$ atoms and their activity in a sample containing over ${10}^{15}$ ${}^{60}\mathrm{Fe}$ atoms. Our new value for the half-life of ${}^{60}\mathrm{Fe}$ is $(2.62\pm 0.04)\times {10}^6\mathrm{yr}$, significantly above the previously reported value of $(1.49\pm 0.27)\times {10}^6\mathrm{yr}$. Our new measurement for the lifetime of ${}^{60}\mathrm{Fe}$ has significant implications for interpretations of galactic nucleosynthesis, for determinations of formation time scales of solids in the early Solar System, and for the interpretation of live ${}^{60}\mathrm{Fe}$ measurements from supernova-ejecta deposits on Earth.

• Received 25 March 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.072502