  Little is known about the stellar environment and the genealogy of our solar
system. Short-lived radionuclides (SLRs, mean lifetime shorter than 100 Myr)
that were present in the solar protoplanetary disk 4.56 Gyr ago could
potentially provide insight into that key aspect of our history, were their
origin understood. Previous models failed to provide a reasonable explanation
of the abundance of two key SLRs, 26Al (mean lifetime = 1.1 Myr) and 60Fe (mean
lifetime = 3.7 Myr), at the birth of the solar system by requiring unlikely
astrophysical conditions. Our aim is to propose a coherent and generic solution
based on the most recent understanding of star-forming mechanisms. Iron-60 in
the nascent solar system is shown to have been produced by a diversity of
supernovae belonging to a first generation of stars in a giant molecular cloud.
Aluminum-26 is delivered into a dense collected shell by a single massive star
wind belonging to a second star generation. The Sun formed in the collected
shell as part of a third stellar generation. Aluminum-26 yields used in our
calculation are based on new rotating stellar models in which 26Al is present
in stellar winds during the star main sequence rather than during the
Wolf-Rayet phase alone. Our scenario eventually constrains the time sequence of
the formation of the two stellar generations that just preceded the solar
system formation, along with the number of stars born in these two generations.
(Continued).
