Origin of short-lived radionuclides

This paper reviews the evidence for short-lived radionuclides in the early Solar System and critically evaluates models for their origin. Radionuclide s with half-lives of less than 50 Myr for which firm and consistent evidenc e has been found are Be-10, Al-26, Ca-41, Mn-53, Fe-60, Pd-107, I-129 and H f-182. The oldest Solar System objects, calcium-aluminium-rich inclusions ( CAIs), contained Be-10, Al-26, Ca-41 and Mn-53 on formation. We discuss whe ther a spallation. or stellar origin for the radionuclides is more likely, and conclude that the initial presence of short-lived radionuclides in CAIs can be most easily explained if these formed by spallation reactions close to the protosun.