20 research outputs found
Origin of Plutonium-244 in the Early Solar System
We investigate the origin in the early Solar System of the short-lived
radionuclide 244Pu (with a half life of 80 Myr) produced by the rapid (r)
neutron-capture process. We consider two large sets of r-process
nucleosynthesis models and analyse if the origin of 244Pu in the ESS is
consistent with that of the other r and slow (s) neutron-capture process
radioactive nuclei. Uncertainties on the r-process models come from both the
nuclear physics input and the astrophysical site. The former strongly affects
the ratios of isotopes of close mass (129I/127I, 244Pu/238U, and 247Pu/235U).
The 129I/247Cm ratio, instead, which involves isotopes of a very different
mass, is much more variable than those listed above and is more affected by the
physics of the astrophysical site. We consider possible scenarios for the
evolution of the abundances of these radioactive nuclei in the galactic
interstellar medium and verify under which scenarios and conditions solutions
can be found for the origin of 244Pu that are consistent with the origin of the
other isotopes. Solutions are generally found for all the possible different
regimes controlled by the interval () between additions from the source
to the parcel of interstellar medium gas that ended up in the Solar System,
relative to decay timescales. If r-process ejecta in interstellar medium are
mixed within a relatively small area (leading to a long ), we derive
that the last event that explains the 129I and 247Cm abundances in the early
Solar System can also account for the abundance of 244Pu. Due to its longer
half life, however, 244Pu may have originated from a few events instead of one
only. If r-process ejecta in interstellar medium are mixed within a relatively
large area (leading to a short ), we derive that the time elapsed from
the formation of the molecular cloud to the formation of the Sun was 9-16 Myr.Comment: 17 pages, 3 figures, published on Universe as part of the Special
Issue "Nuclear Astrophysics in the Era of High Precision Astronomy