Most star formation in the Galaxy takes place in clusters , where the most massive members can affect the properties of other constituent solar systems .
This paper considers how clusters influence star formation and forming planetary systems through nuclear enrichment from supernova explosions , where massive stars deliver short-lived radioactive nuclei ( SLRs ) to their local environment .
The decay of these nuclei leads to both heating and ionization , and thereby affects disk evolution , disk chemistry , and the accompanying process of planet formation .
Nuclear enrichment can take place on two spatial scales : [ 1 ] Within the cluster itself ( \ell \sim 1 pc ) , the SLRs are delivered to the circumstellar disks associated with other cluster members .
[ 2 ] On the next larger scale ( \ell \sim 2 - 10 pc ) , SLRs are injected into the background molecular cloud ; these nuclei provide heating and ionization to nearby star-forming regions , and to the next generation of disks .
For the first scenario , we construct the expected distributions of radioactive enrichment levels provided by embedded clusters .
Clusters can account for the SLR mass fractions inferred for the early Solar Nebula , but typical SLR abundances are lower by a factor of \sim 10 .
For the second scenario , we find that distributed enrichment of SLRs in molecular clouds leads to comparable abundances .
For both the direct and distributed enrichment processes , the masses of ^ { 26 } Al and ^ { 60 } Fe delivered to individual circumstellar disks typically fall in the range 10 - 100 pM _ { \odot } ( where 1 pM _ { \odot } = 10 ^ { -12 } M _ { \odot } ) .
The corresponding ionization rate due to SLRs typically falls in the range \zeta _ { SLR } \sim 1 - 5 \times 10 ^ { -19 } sec ^ { -1 } .
This ionization rate is smaller than that due to cosmic rays , \zeta _ { CR } \sim 10 ^ { -17 } sec ^ { -1 } , but will be important in regions where cosmic rays are attenuated ( e.g. , disk mid-planes ) .