The abundances of short-lived radionuclides in the early solar system ( ESS ) are reviewed , as well as the methodology used in determining them .
These results are compared with the inventory estimated for a uniform galactic production model .
It is shown that , to within a factor of two , the observed abundances of ^ { 238 } U , ^ { 235 } U , ^ { 232 } Th , ^ { 244 } Pu , ^ { 182 } Hf , ^ { 146 } Sm , and ^ { 53 } Mn are roughly compatible with long-term galactic nucleosynthesis . ^ { 129 } I is an exception , with an ESS inventory much lower than expected from uniform production .
The isotopes ^ { 107 } Pd , ^ { 60 } Fe , ^ { 41 } Ca , ^ { 36 } Cl , ^ { 26 } Al , and ^ { 10 } Be require late addition to the protosolar nebula . ^ { 10 } Be is the product of energetic particle irradiation of the solar system as most probably is ^ { 36 } Cl .
Both of these nuclei appear to be present when ^ { 26 } Al is absent .
A late injection by a supernova ( SN ) can not be responsible for most of the short-lived nuclei without excessively producing ^ { 53 } Mn ; it can however be the source of ^ { 53 } Mn itself and possibly of ^ { 60 } Fe .
If a late SN injection is responsible for these two nuclei , then there remains the problem of the origin of ^ { 107 } Pd and several other isotopes .
Emphasis is given to an AGB star as a source of many of the nuclei , including ^ { 60 } Fe ; this possibility is explored with a new generation of stellar models .
It is shown that if the dilution factor ( i.e .
the ratio of the contaminating mass to the solar parental cloud mass ) is f _ { 0 } \sim 4 \times 10 ^ { -3 } , a reasonable representation for many nuclei is obtained ; this requires that ( ^ { 60 } Fe/ ^ { 56 } Fe ) _ { ESS } \sim 10 ^ { -7 } to 2 \times 10 ^ { -6 } .
The nuclei produced by an AGB source do not include ^ { 53 } Mn , ^ { 10 } Be or ^ { 36 } Cl if it is very abundant .
The role of irradiation is discussed with regard to ^ { 26 } Al , ^ { 36 } Cl and ^ { 41 } Ca , and the estimates of bulk solar abundances of these isotopes are commented on .
The conflict between various scenarios is emphasized as well as the current absence of an astrophysically plausible global interpretation for all the existing data .
Examination of abundances for the actinides indicates that a quiescent interval of \sim 10 ^ { 8 } years is required for actinide group production .
This is needed in order to explain the data on ^ { 244 } Pu and the new bounds on ^ { 247 } Cm .
Because this quiescent interval is not compatible with the ^ { 182 } Hf data , a separate type of r -process event is needed for at least the actinides , distinct from the two types that have previously been identified .
The apparent coincidence of the ^ { 129 } I and trans-actinide time scales suggests that the last heavy r contribution was from an r -process that produced very heavy nuclei but without fission recycling so that the yields at Ba and below ( including I ) were governed by fission .