Short-lived nuclides in the early solar system and general isotopic anomalies in meteorites

A brief review is presented of the evidence for short-lived nuclides in the early solar system. The presence of these nuclides requires the addition to the interstellar medium from which the solar system formed of freshly synthesized materials just prior to the formation of the solar system. The nuclides with the shortest half-lives and identified as present in the solar system provide the strictest time-scale for the last injection. The presence of general isotopic anomalies has been established for many elements through a wide range in atomic number. Multiple nucleosynthetic processes are required, but the general effects can be consistent with a generic model of an exploding massive star. The most distinctive components are obtained by the measurements of correlated isotopic anomalies over a range in atomic numbers, for neighboring elements. The general isotopic anomalies observed for many elements may represent either addition of exotic components to the protosolar cloud or may reflect the incomplete mixing of diverse nucleosynthetic components within the interstellar medium. The effects due to short-lived nuclides require a short time between the last contributions to the solar system from nucleosynthesis and the formation of cm-sized inclusions and of small planets within the solar system