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Supernova Sources and the 92Nb-92Zr p-Process Chronometer.
The Astrophysical Journal
|June 13, 2000
Summary
New evidence shows live Niobium-92 (92Nb) existed in the early solar system. This finding supports the theory that extinct isotopes like 92Nb were uniformly produced by Type II supernovae.
Area of Science:
- Cosmochemistry
- Nuclear Astrophysics
- Early Solar System Studies
Background:
- The presence of extinct radionuclides in the early solar system provides insights into nucleosynthesis and the timing of solar system formation.
- Niobium-92 (92Nb) is an extinct radionuclide whose presence and production pathways are crucial for understanding early solar system processes.
Purpose of the Study:
- To investigate the presence and implications of live Niobium-92 (92Nb) in the early solar system using Zr isotope evidence.
- To explore the (92)Nb-(92)Zr chronometer in meteoritic minerals.
Main Methods:
- Analysis of Zr isotope anomalies (epsilon92Zr) in meteoritic minerals (rutile and zircon) with varying Nb/Zr ratios.
- Comparison of observed isotopic signatures with models of nucleosynthetic production from Type II supernovae (SNII).
Main Results:
- Meteoritic rutiles show high positive epsilon92Zr values (approx. 14-36), while a zircon exhibits a negative value (approx. -4), consistent with live 92Nb.
- Apparent formation times for meteoritic rutiles are estimated at 80-220 Myr after the solar system's origin.
- The initial (92)Nb/(92)Mo ratio is compatible with uniform production from SNII sources with neutrino-driven winds.
Conclusions:
- The study provides strong evidence for live 92Nb in the early solar system.
- Observed isotopic data for extinct p-process nuclides (92Nb, 97Tc, 146Sm) support uniform production from SNII sources.
- The average p-process production ratio of (92)Nb/(92)Mo is constrained to be at least 0.06-0.25.