Possible Implications of Relatively High Levels of Initial 60Fe in Iron Meteorites for the Noncarbonaceous-Carbonaceous Meteorite Dichotomy and Solar Nebula Formation
Abstract
Cook et al. found that iron meteorites have an initial abundance ratio of the short-lived isotope 60Fe to the stable isotope 56Fe of 60Fe/56Fe ~ (6.4 ± 2.0) × 10-7. This appears to require the injection of live 60Fe from a Type II supernova (SN II) into the presolar molecular cloud core, as the observed ratio is over a factor of 10 times higher than would be expected to be found in the ambient interstellar medium (ISM) as a result of galactic chemical evolution. The supernova triggering and injection scenario offers a ready explanation for an elevated initial 60Fe level, and in addition provides a physical mechanism for explaining the noncarbonaceous-carbonaceous (NC-CC) dichotomy of meteorites. The NC-CC scenario hypothesizes the solar nebula first accreted material that was enriched in supernova-derived nuclides, and then later accreted material depleted in supernova-derived nuclides. While the NC-CC dichotomy refers to stable nuclides, not short-lived isotopes like 60Fe, the SN II triggering hypothesis provides an explanation for the otherwise unexplained change in nuclides being accreted by the solar nebula. Three-dimensional hydrodynamical models of SN II shock-triggered collapse show that after triggering collapse of the presolar cloud core, the shock front sweeps away the local ISM while accelerating the resulting protostar/disk to a speed of several kilometers per second, sufficient for the protostar/disk system to encounter within ~1 Myr the more distant regions of a giant molecular cloud complex that might be expected to have a depleted inventory of supernova-derived nuclides.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2022
- DOI:
- 10.3847/1538-4357/ac6609
- arXiv:
- arXiv:2204.04134
- Bibcode:
- 2022ApJ...933....1B
- Keywords:
-
- Planet formation;
- Star formation;
- Hydrodynamics;
- Protoplanetary disks;
- Supernova remnants;
- 1241;
- 1569;
- 1963;
- 1300;
- 1667;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 26 pages, 14 figures, accepted for ApJ