Short-lived nuclides in the early solar system: the stellar connection

Fossil evidence for the presence of short-lived nuclides with half-life ranging from 100,000 years to similar to100 million years (Ma) in the early solar system has been found in primitive meteorites. The nuclides with half-life less than a couple of million years (Ca-41, Al-26, Be-10 Fe-60) must have been produced either shortly before or during the very early evolution of the solar system. Two plausible sources of these nuclides are proposed; a single stellar source (e.g., a TP-AGB star, supernova or a W-R star) or energetic particle production in solar, presolar or stellar environments. The presence of Be-10, which is not a product of stellar nucleosynthesis, argues for an energetic particle production mechanism. However, correlated presence of Ca-41 and Al-26 with well-defined initial abundances in early solar system objects cannot be explained in the energetic particle production model and it also fails to account for the presence of Fe-60. Recent experimental data demonstrate that the source of Be-10 is decoupled from that of Al-26 and Ca-41 and suggest that both a stellar source as well as energetic particle production contributed to the inventory of the short-lived nuclides in the early solar system. New data for initial abundance of Fe-60 in the solar system tend to favor a SN source. The presence of freshly synthesized short-lived nuclides from an evolved star in the early solar system led to the hypothesis of a triggered origin of the solar system. Numerical simulation studies indicate dynamical feasibility of such a process and there are indirect observational evidences for triggered formation of sun-like stars. (C) 2003 Elsevier B.V. All rights reserved.