Nuclear cosmochronometer and universality in the r-process abundance distribution

We show that, a variety of astrophysical r-process models can be constructed which reproduce the observed universal r-process curve for 56 < Z < 80 nuclei, yet have vastly different abundances for Z > 80 and Z < 56 elements. It is dangerous to use the Th/Eu chronometer to estimate the age of metal deficient stars. We do find, however, that the U/Th production ratio is almost independent of the nucleosynthesis environment and could therefore be good chronometer.