Radioactive nuclei with lifetimes on the order of millions of years can reveal the formation history of the Sun and active nucleosynthesis occurring at the time and place of its birth^(1,2). Among such nuclei whose decay signatures are found in the oldest meteorites, ^(205)Pb is a powerful example, as it is produced exclusively by slow neutron captures (the s process), with most being synthesized in asymptotic giant branch (AGB) stars^(3-5). However, making accurate abundance predictions …