SUPERNOVA PROPAGATION AND CLOUD ENRICHMENT: A NEW MODEL FOR THE ORIGIN OF 60Fe IN THE EARLY SOLAR SYSTEM

The radioactive isotope Fe-60 (T-1/2 = 1.5 Myr) was present in the early solar system. It is unlikely that it was injected directly into the nascent solar system by a single, nearby supernova (SN). It is proposed instead that it was inherited during the molecular cloud (MC) stage from several SNe belonging to previous episodes of star formation. The expected abundance of Fe-60 in star-forming regions is estimated taking into account the stochasticity of the star-forming process, and it is showed that many MCs are expected to contain Fe-60 ( and possibly Al-26 [T-1/2 = 0.74 Myr]) at a level compatible with that of the nascent solar system. Therefore, no special explanation is needed to account for our solar system's formation.