New Study Pinpoints Sun's Formation Time to 10-20 Million Years

An international team of scientists has refined the estimated formation time of our Sun, placing it between 10 to 20 million years. This conclusion, published in *Nature*, stems from the measurement of a rare nuclear process involving the decay of thallium-205 (²⁰⁵Tl) in a fully ionized state. The experiment was conducted at the Experimental Storage Ring (ESR) of GSI/FAIR in Germany. The research focused on how lead-205 (²⁰⁵Pb), an isotope crucial for dating the Sun's birth, is formed in asymptotic giant branch (AGB) stars. ²⁰⁵Pb is created through the slow neutron capture process (s-process), making it a reliable marker for stellar formation timelines. Normally, ²⁰⁵Pb decays to ²⁰⁵Tl via electron capture. However, in the high-temperature, fully ionized conditions of stars, this process reverses, with ²⁰⁵Tl decaying to ²⁰⁵Pb through bound-state beta decay. Scientists successfully observed this rare decay and measured its rate. Researchers from Hungary, Italy, and the UK used these findings to model ²⁰⁵Pb production in AGB stars. By comparing the predicted ²⁰⁵Pb levels with those found in meteorites, they estimated the Sun's formation period. The team included 37 scientific institutions from 12 countries and involved a decade of advanced experimental work. This measurement offers new insights into nuclear processes in stars, enhancing our understanding of the solar system's origins.