60Fe in Chondrites: Debris from a Nearby Supernova in the Early Solar System?
60Fe in Chondrites: Debris from a Nearby Supernova in the Early Solar System?
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DOI：
10.1086/503201
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发表时间：
2006-02
期刊：
影响因子：
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通讯作者：
S. Tachibana;G. Huss;N. Kita;G. Shimoda;Y. Morishita
中科院分区：
文献类型：
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作者：
S. Tachibana;G. Huss;N. Kita;G. Shimoda;Y. Morishita
60Fe衰变为60Ni，半衰期为1.49 × 106年，所以太阳系中原来所有的60Fe原子都衰变了。因为60Fe只在恒星中产生，所以它在太阳系中最初的丰度限制了放射性核素对早期太阳系的贡献以及恒星来源的性质。由于它的半衰期很短，60Fe也可能是早期太阳系事件的高分辨率计时器。原始陨石中60Fe的存在已经在硫化物中得到证实，但由于不确定硫化物是何时形成的，所以太阳系中60Fe的初始丰度只是受到了松散的限制。结果表明，镁铁球粒形成时存在60Fe，丰度比为60Fe/56Fe = (2.2 ~ 3.7) × 10-7。利用已知最古老的太阳系固体——富钙铝包裹体（CAIs）与氧化铁球粒形成的150 - 200万年的时间差，估算出太阳系初始60Fe/56Fe比值[(60Fe/56Fe)0]为（5-10）× 10-7。这个新的基于固体的（60Fe/56Fe）0比率与在太阳系形成之前超新星或中等质量渐近巨支（AGB）恒星中核合成的预测一致，但对于低质量AGB恒星的来源来说太高了。考虑到分子云和AGB恒星相遇的罕见性，我们的结果可以被认为是附近超新星物质贡献的有力证据，以及超新星在太阳系起源中的作用。
60Fe decays to 60Ni with a half-life of 1.49 × 106 yr, so all of the original 60Fe atoms incorporated into the solar system have decayed. Because 60Fe is produced only in stars, its initial abundance in the solar system provides a constraint on the stellar contribution of radionuclides to the early solar system and on the nature of the stellar source. Because of its short half-life, 60Fe is also a potential high-resolution chronometer of early-solar-system events. The presence of 60Fe in primitive meteorites has been confirmed in sulfides, but the initial abundance of 60Fe in the solar system has been only loosely constrained because it is uncertain when the sulfides formed. We show that 60Fe was present with abundance ratios of 60Fe/56Fe = (2.2-3.7) × 10-7 when ferromagnesian chondrules formed. By applying the time difference of 1.5-2.0 million years between formation of ferromagnesian chondrules and Ca-Al-rich inclusions (CAIs), the oldest known solar system solids, a solar system initial 60Fe/56Fe ratio [(60Fe/56Fe)0] of (5-10) × 10-7 is estimated. This new solidly based (60Fe/56Fe)0 ratio is consistent with predictions for nucleosynthesis in a supernova or in an intermediate-mass asymptotic giant branch (AGB) star just before the solar system formation, but is too high for the source to have been a low-mass AGB star. Considering the rarity of encounters between a molecular cloud and an AGB star, our results can be considered strong evidence of a contribution of material from a nearby supernova and of a role for a supernova in the origin of the solar system.