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Meteoritic evidence of a late superflare as source of 7Be in the early Solar System

Nature Astronomy (2019) | Download Citation


Fossil meteoritic records of short-lived, now-extinct radionuclides provide crucial high-resolution temporal information about the events, processes and activity of the Sun during the early phases of Solar System formation1. The proposed genesis of one such radionuclide,10Be, by spallation reactions of carbon and oxygen2,3,4,5 led to the hypothesis of enhanced irradiation in the early Solar System6,7,8. An alternative scenario of production of 10Be (half-life t1/2 = 1.386 ± 0.016 million years9) by a neutrino process in a supernova arising from the core collapse of a low-mass star (11.8 solar masses, M) has recently been suggested10 and can explain the observed abundance of 10Be in the early Solar System. Here, we report well-resolved excesses in 7Li/6Li of up to ~21.5% in a calcium- and aluminium-rich inclusion (CAI) from the Efremovka meteorite that correlate with 9Be/6Li, suggestive of in situ decay of 7Be. The in situ decay of 7Be to 7Li, with a characteristic half-life of 53.12 ± 0.07 days11, entails multiple episodes of enhanced irradiation in the early Solar System, which have been observed recently in other Sun-like stars12,13. The short half-life of 7Be limits its production by interaction of solar energetic particles (SEPs) with the nebular gas and solids, and provides constraints on the genealogy and chronology of CAIs. Irradiation of the solid and gaseous precursors of CAIs of solar composition by a superflare (X-ray luminosity approximately 1032 erg s−1) during the terminal phase of class I or II of the pre-main-sequence stages of the Sun explains the isotopic properties, distinctive petrographic features and diffusivity constraints in the CAI.

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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Journal peer review information: Nature Astronomy thanks Don Burnett and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Secondary ion mass spectrometry (SIMS) at the Physical Research Laboratory, Ahmedabad, India is supported partially by financial grants from Department of Space, Government of India. K.K.M. acknowledges support for the research from Scientific and Engineering Research Board, India (SERB-WES grant no. SB/WEA-007/2013). R.K.M. acknowledges financial support during the preliminary preparation of the manuscript at NASA Johnson Space Center, Houston under a NASA post-doctoral programme (NPP) fellowship administered by the Oak Ridge National Laboratory associated universities, and from the Alexander Von Humboldt foundation during the Humboldt fellowship at Ruprecht-Karls University, Heidelberg. We acknowledge discussions over the years with J. N. Goswami, M. Chaussidon and J. I. Simon. We thank M. Trieloff and J. B. Patel for comments. V. Goyal, Sameer and A. Cisneros helped in the preparation of Fig. 2. We dedicate this paper to the late Professor Devendra Lal.

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Author notes

    • Ritesh Kumar Mishra

    Present address: Klaus-Tschira-Labor für Kosmochemie, Institut für Geowissenschaften, Ruprecht-Karls-Universität, Heidelberg, Germany


  1. Center for Isotope Cosmochemistry and Geochronology, Astromaterials Research and Exploration Science Division EISD-XI, NASA-Johnson Space Center, Houston, TX, USA

    • Ritesh Kumar Mishra
  2. Planetary Sciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad, India

    • Kuljeet Kaur Marhas


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R.K.M. and K.K.M. planned the project and contributed equally towards analysis of the data. K.K.M. performed the ion probe analysis and model calculation. R.K.M. and K.K.M. discussed the results and wrote the manuscript. Reprints and permissions information is available at www.nature.com/reprints.

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The authors declare no competing interests.

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Correspondence to Ritesh Kumar Mishra.

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