  Understanding the origin of the elements has been a decades long pursuit,
with many open questions still remaining. Old stars found in the Milky Way and
its dwarf satellite galaxies can provide answers because they preserve clean
elemental patterns of the nucleosynthesis processes that operated some 13
billion years ago. This enables the reconstruction of the chemical evolution of
the elements. Here we focus on the astrophysical signatures of heavy
neutron-capture elements made in the s-, i- and r-process found in old stars. A
highlight is the recently discovered r-process galaxy Reticulum II that was
apparently enriched by a neutron star merger. These results show that old stars
in dwarf galaxies provide a novel means to constrain the astrophysical site of
the r-process, ushering in much needed progress on this major outstanding
question. This nuclear astrophysics work complements the many nuclear physics
efforts into heavy-element formation, and aligns with recent results on the
gravitational wave signature of a neutron star merger.
