2025ApJ...988...22H

The abundance ratios of radioactive elements U/Th and stable elements Pb/Os from the r-process are found to have a strong correlation. This correlation is quite robust with respect to astrophysical conditions. The U/Th-Pb/Os correlation is applied to provide customized initial abundance ratios U/Th from the observed abundance ratios Pb/Os for six r-process enhanced metal-poor stars. The ages of these six metal-poor stars are predicted by the U/Th chronometer, which are approximately between 11 and 15 Gyr. Their ages are compatible with the cosmic age of 13.8 billion years predicted from the cosmic microwave background radiation.