Wallner A, Feige J, Kinoshita N, Paul M, Fifield L K, Golser R, Honda M, Linnemann U, Matsuzaki H, Merchel S, Rugel G, Tims S G, Steier P, Yamagata T, Winkler S R
Department of Nuclear Physics, Research School of Physics and Engineering, The Australian National University (ANU), Canberra, Australian Capital Territory 2601, Australia.
University of Vienna, Faculty of Physics-Isotope Research, VERA Laboratory, Währinger Straße 17, 1090 Vienna, Austria.
Nature. 2016 Apr 7;532(7597):69-72. doi: 10.1038/nature17196.
The rate of supernovae in our local Galactic neighbourhood within a distance of about 100 parsecs from Earth is estimated to be one every 2-4 million years, based on the total rate in the Milky Way (2.0 ± 0.7 per century). Recent massive-star and supernova activity in Earth's vicinity may be traced by radionuclides with half-lives of up to 100 million years, if trapped in interstellar dust grains that penetrate the Solar System. One such radionuclide is (60)Fe (with a half-life of 2.6 million years), which is ejected in supernova explosions and winds from massive stars. Here we report that the (60)Fe signal observed previously in deep-sea crusts is global, extended in time and of interstellar origin from multiple events. We analysed deep-sea archives from all major oceans for (60)Fe deposition via the accretion of interstellar dust particles. Our results reveal (60)Fe interstellar influxes onto Earth at 1.5-3.2 million years ago and at 6.5-8.7 million years ago. The signal measured implies that a few per cent of fresh (60)Fe was captured in dust and deposited on Earth. Our findings indicate multiple supernova and massive-star events during the last ten million years at distances of up to 100 parsecs.
根据银河系的总爆发率（每世纪2.0±0.7次）估算，在距离地球约100秒差距的本地星系邻域内，超新星爆发的频率约为每200万至400万年一次。如果被困在穿透太阳系的星际尘埃颗粒中，半衰期长达1亿年的放射性核素可以追溯到地球附近近期的大质量恒星和超新星活动。其中一种放射性核素是铁-60（半衰期为260万年），它在超新星爆发以及大质量恒星的星风中被喷射出来。在此，我们报告称，先前在深海地壳中观测到的铁-60信号是全球性的，时间上具有延续性，且源自多个事件的星际物质。我们分析了所有主要大洋的深海沉积物档案，以研究通过星际尘埃颗粒的堆积而产生的铁-60沉积情况。我们的研究结果揭示，在距今约150万至320万年以及650万至870万年前，铁-60曾有星际物质流入地球。测量到的信号表明，有百分之几的新鲜铁-60被尘埃捕获并沉积到了地球上。我们的研究结果表明，在过去的一千万年里，距离地球达100秒差距范围内发生了多次超新星和大质量恒星事件。
