Determination of the Galaxy age by the method of uraniumâEuro"thoriumâEuro"plutonium isotopic ratios

The dependence of the Galaxy age (D cent (G)), as determined by the method of uranium-thorium isotopic ratios, on the parameters of the nucleosynthesis model is studied within the theory of galactic nucleosynthesis. It is shown that D cent G depends strongly both on the scenario of the production of nuclei in the r-process and those features of neutron-rich nuclei that are used in the respective analysis and on galactic-nucleosynthesis parameters. The effect of a sudden nucleosynthesis spike before the formation of a solar system on the Galaxy age is evaluated. The region of admissible values of the parameters of galacticnucleosynthesis theory is discussed. The method of uranium-thorium isotopic ratios is supplemented with the Pu-244/U-238 ratio for yet another cosmochronometer pair, and the Galaxy age is estimated on the basis of the model modified in this way.