The RADIOSTAR Project
  Radioactive nuclei are the key to understanding the circumstances of the
birth of our Sun because meteoritic analysis has proven that many of them were
present at that time. Their origin, however, has been so far elusive. The
ERC-CoG-2016 RADIOSTAR project is dedicated to investigating the production of
radioactive nuclei by nuclear reactions inside stars, their evolution in the
Milky Way Galaxy, and their presence in molecular clouds. So far, we have
discovered that: (i) radioactive nuclei produced by slow ($^{107}$Pd and
$^{182}$Hf) and rapid ($^{129}$I and $^{247}$Cm) neutron captures originated
from stellar sources - asymptotic giant branch (AGB) stars and compact binary
mergers, respectively - within the galactic environment that predated the
formation of the molecular cloud where the Sun was born; (ii) the time that
elapsed from the birth of the cloud to the birth of the Sun was of the order of
10$^7$ years, and (iii) the abundances of the very short-lived nuclei
$^{26}$Al, $^{36}$Cl, and $^{41}$Ca can be explained by massive star winds in
single or binary systems, if these winds directly polluted the early Solar
System. Our current and future work, as required to finalise the picture of the
origin of radioactive nuclei in the Solar System, involves studying the
possible origin of radioactive nuclei in the early Solar System from
core-collapse supernovae, investigating the production of $^{107}$Pd in massive
star winds, modelling the transport and mixing of radioactive nuclei in the
galactic and molecular cloud medium, and calculating the galactic chemical
evolution of $^{53}$Mn and $^{60}$Fe and of the p-process isotopes $^{92}$Nb
and $^{146}$Sm.
