Influence of the Change in the Galactic-Nucleosynthesis Rate before the Formation of Solar System on the Determination of Age of The Universe

Resumo

The dependence of the region of physically admissible values of uranium-thorium isotope ratios on the short-term change in nucleosynthesis rate, which increases just before the formation of the Solar system, is studied. An additional admissible region associated with the presence of the isotope ²⁴⁴Pu and the effect of this region on the calculation of the age of the Universe, T_U, are considered within galactic-nucleosynthsis theory. The size of the admissible region and its dependence on the short-term increase in the rate of heavy-element production (enhancement of nucleosynthsis) before the formation of the Solar System is discussed along with the consistency of the predictions for the above ratios with the region of admissible values. It is shown that an enhancement of nucleosynthesis is necessary for attaining agreement between the calculated ratios of cosmochronometer nuclei and the region of admissible values, but this enhancement should not lead to an increase in the abundances of heavy elements that is greater than 1 to 3% of the total amount of synthesized heavy elements.