Document Type: Regular Paper
Islamic Azad University, Shiraz Branch, I. R. of Iran
The independent model used by Meyer and Schramm (here after M&S) for determining the age of
elements (chemical evolution) is extended. Using new and extended definitions and including parameters
ignored by M&S, the galactic evolution equations are solved to determine the total duration of
nucleosynthesis,T. To be able to calculate the t T (mean age time for formation of elements to total duration of nucleosynthesis ratio), one event age, max ij , and r(i, j) are determined using approximation relating r(i, j) to the former value r(i, j). For Th/U pair, constraint on t T becomes 0.43 t T 0.61 and the age of the galaxy is obtained as 12.5 23.0 Gal Gyr T Gyr , reducing the variation considerably
compared to M&S formalism ( 8.7Gyr TGal 28.1 Gyr ). The range of constraints for the age of the
universe is shorter than the M&S and our modifications on the model have reduced the interval for galaxy age 83% and close to being concordant with other available methods.