A lot of information can be gained from stellar spectra e.g. the
stellar ages, velocities, evolutionary stage, abundances, as
well as the composition of the environment they were born in.
High quality spectra allow us to derive stellar abundances of
about 2/3 of the elements in the periodic table. By comparing
abundances of elements belonging to different groups in the
periodic table, we can gain information about long gone
supernovae - maybe even the first ones? These supernovae
enriched the gas we observe today in later generations of stars.
To date we still do not fully understand how the heavy elements
(Z > 37) are formed. Two main production channels are known to
create the majority of the heavy elements through neutron
captures, namely the rapid neutron capture (r-)process and the
slow neutron-capture (s-)process. Recently we have seen that
each of these production channels seem to branch into two, a
main and a weak process. The nature of weak s-process is fairly
well known, while the weak r-process rem