  We investigate $^{60}$Fe in massive stars and core-collapse supernovae
focussing on uncertainties that influence its production in 15, 20 and 25
$M_\odot$ stars at solar metallicity. We find that the $^{60}$Fe yield is a
monotonic increasing function of the uncertain $^{59}$Fe$(n,\gamma)^{60}$Fe
cross section and that a factor of 10 reduction in the reaction rate results in
a factor 8-10 reduction in the $^{60}$Fe yield; while a factor of 10 increase
in the rate increases the yield by a factor 4-7. We find that none of the 189
simulations we have performed are consistent with a core-collapse supernova
triggering the formation of the Solar System, and that only models using
$^{59}$Fe$(n,\gamma)^{60}$Fe cross section that is less than or equal to that
from NON-SMOKER can reproduce the observed $^{60}$Fe/$^{26}$Al line flux ratio
in the diffuse ISM. We examine the prospects of detecting old core-collapse
supernova remnants (SNRs) in the Milky Way from their $\gamma$-ray emission
from the decay of $^{60}$Fe, finding that the next generation of gamma-ray
missions could be able to discover up to $\sim100$ such old SNRs as well as
measure the $^{60}$Fe yields of a handful of known Galactic SNRs. We also
predict the X-ray spectrum that is produced by atomic transitions in $^{60}$Co
following its ionization by internal conversion and give theoretical X-ray line
fluxes as a function of remnant age as well as the Doppler and fine-structure
line broadening effects. The X-ray emission presents an interesting prospect
for addressing the missing SNR problem with future X-ray missions.
