Special Seminar – Francois Tissot

Francois Tissot
Crosby Postdoctoral Fellow, EAPS

Solar System formation and nucleosynthesis of heavy elements:
a perspective from fine-grained CAIs.

The elemental and isotopic composition of planets, meteorites and their inclusions is the result of a long succession of processes from nucleosynthesis to planetary differentiation. By measuring the elemental and isotopic compositions of these bodies, we can thus study the processes that shaped our solar system. In this talk, I will present how measurements of the U and Mg isotopes composition of fine-grained CAIs (some of the first solids formed in the Solar System) changed our understanding of the rapid neutron capture process of nucleosynthesis (the r-process), which produces the heaviest elements in the Galaxy.

Current models talk of up to three different r-processes producing heavy elements with different atomic numbers: one process would synthesize the lighter r-nuclides (A140) and yet another one the actinides (e.g., 244Pu). These interpretations are based on the meteoritic abundance of only three short-lived r-nuclides (129I, 182Hf, 244Pu). Taken at face value, there are as many types of r-processes as short-lived r-nuclides investigated so far.

247Cm, which decays into 235U with a half-life of 15.6 Myr, is the obvious next r-nuclide to chase to shed new light on this picture. The only problem is that, despite numerous attempts, 247Cm has eluded detection for the past 40 years. In this seminar, I will present how we went about chasing 247Cm, how we found it in a particular subset of CAIs, and what the implications for the formation of the Solar System and the nucleosynthesis of heavy elements are.

Seminar at 3PM in room 54-915
Reception to follow

Questions? email provaire@mit.edu