Constraint on the cosmic age from the solar r-process abundances

The cosmic age is an important physical quantity in cosmology. Based on the radiometric method, a reliable lower limit of the cosmic age is derived to be 15.68±1.94 Gyr, using the r-process abundances inferred for the solar system and observations in metal-poor stars. If the central value is taken, this value is larger than the latest cosmic age 13.813±0.058 Gyr determined from Planck 2013 results; however, the two agree with each other within uncertainties. The uncertainty of 1.94 Gyr mainly originates from the error on thorium abundance observed in metal-poor star CS 22892-052, so future high-precision abundance observations on CS 22892-052 are valuable to further check the cosmic age determined from different independent methods. On the other hand, by taking the cosmic age from Planck 2013 results as a standard value, the lower limit of abundance ratios Th/X and U/X in metal-poor stars is deduced as a guidance to future observations. (paper)