Dr. Sofia Randich, INAF-Arcetri

"Age dating young and old stars using light elements"

Abstract:
Lithium and beryllium measurements in stars offer a secure and independent
way to derive stellar ages.
Specifically, determination of surface Li abundance in fully convective,
low-mass members of young clusters provide a very useful clock to estimate
nuclear ages that can be compared to the isochronal ages derived from
the star's location in the HR diagram.
On the other hand, observations of Be in old Pop. II stars represent an ideal
"cosmic clock" for age dating the first stages of Galactic halo evolution.

In this context, I will present recent results from Li measurements in
young associations and Be determinations in old globular clusters,
respectively. The implications for the young cluster star formation histories,
as well as for our understanding of Galaxy formation and early evolution
will be discussed.