Short-lived radioactivities in the early solar system: A fossil record of our origins in stars

The measurements, revealing that several radioactive nuclei, with half-lives from 0.1 to 20 Myr, were present, alive, in the Early Solar System, are reviewed. The literature recently published for attempting an astrophysical explanation of their concentrations is then discussed, underlining how several uncertainties still hamper our capability of explaining this crucial data set, informing us on our origins. Galactic evolution can broadly account for most of the above nuclei, but the shortest-lived ones (26Al, 41Ca, 135Cs and perhaps 60Fe) require some nucleosynthesis event very close in time and in space to the forming Sun. The difficulties met by stellar nucleosynthesis in intermediate-mass stars (IMSs: 2≤M/M⊙≤7\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ 2 \leq {\rm M/M}_{\odot} \leq 7$\end{document}-8) and in massive stars (MSs; M/M⊙≤10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ {\rm M/M}_{\odot} \leq 10$\end{document}) are then presented and it is illustrated how also the expected pollution of the interstellar medium by multiple previously estinguished stars in a possible cluster or association in which the Sun might have formed may not solve the problems, so that short-lived radioactivities remain as a challenging constraint for nuclear astrophysics.