  The kilonova associated with the neutron star merger GW170817 provides us
with several hints to elucidate the nature of the r-process in the universe. In
this article, we inspect the radioactive isotopes that powered the kilonova
emission, provided that the merger ejecta consisted of material with a solar
r-like abundance pattern. It is suggested that the early (1-10 days after
merger) kilonova emission is mainly due to the beta-decay chain 66Ni -> 66Cu ->
66Zn, which can be the source of the steepening of the light curve at about 7
days. The late time (> 10 days) heaing is attributed to the alpha-decay and
fission (254Cf) of trans-Pb species (in addition to beta-decay), which can be
the signature of r-processing beyond the heaviest stable elements. This article
summarizes a recent work by the author (Wanajo 2018) with the additional
calculations of kilonova light curves by using a numerical code in Hotokezaka
and Nakar (2019).
