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r-Process elements from magnetorotational hypernovae


Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1,2,3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4,5,6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7,8,9,10,11,12,13. Here we report the element abundance pattern of the extremely metal-poor star SMSS J200322.54−114203.3. We observe a large enhancement in r-process elements, with very low overall metallicity. The element abundance pattern is well matched by the yields of a single 25-solar-mass magnetorotational hypernova. Such a hypernova could produce not only the r-process elements, but also light elements during stellar evolution, and iron-peak elements during explosive nuclear burning. Hypernovae are often associated with long-duration γ-ray bursts in the nearby Universe8. This connection indicates that similar explosions of fast-spinning strongly magnetized stars occurred during the earliest epochs of star formation in our Galaxy.

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Fig. 1: r-Process element abundance pattern of SMSS 2003−1142.
Fig. 2: Comparison of models and data.

Data availability

The data used in this study are available in the ESO archive ( under program ID 2103.D-5062(A).

Code availability

The stellar line analysis program MOOG is available at The stellar model atmospheres are available at


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This paper includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile, and is based on observations collected at the European Southern Observatory under ESO programme DDT 2103.D-5062(A). This research was supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. C.K. acknowledges funding from the UK Science and Technology Facility Council (STFC) through grant ST/M000958/1 and ST/ R000905/1, and the Stromlo Distinguished Visitor Program at ANU. K.L. acknowledges funds from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 852977). A.F.M. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement number 797100. A.R.C. acknowledges Australian Research Council grant DE190100656.

Author information




G.S.D.C., M.S.B., M.A., A.D.M., A.F.M., S.J.M. and T.N. were involved in the target selection and low-resolution spectroscopic observation campaigns. D.Y., G.S.D.C., A.C., A.F. and T.N. were involved in the high-resolution spectroscopic observations. K.L. and T.N. computed the non-LTE corrections. The manuscript was written by D.Y., C.K. and G.S.D.C., with contributions from all authors.

Corresponding author

Correspondence to D. Yong.

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The authors declare no competing interests.

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Peer review information Nature thanks Timothy Beers and Kim Venn for their contribution to the peer review of this work. Peer reviewer reports are available.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Spectrum of SMSS 2003−1142.

a, b, Spectrum synthesis fit to the 4,810-Å Zn i line (a) and the 4,129-Å Eu ii line (b). The observed spectra are shown as small circles, the best-fitting synthetic spectrum is shown as the solid black line and the yellow region indicates ±0.2 dex from the best fit.

Extended Data Fig. 2 Abundance ratios in halo stars.

af, Element to Fe ratios, [X/Fe], as a function of metallicity, [Fe/H], based on literature data20 (small crosses), for C (a), N (b), Zn (c), Ba (d), Eu (e) and Th (f). The lines are the Galactic chemical evolution model predictions for the solar neighbourhood20. SMSS 2003−1142 is shown as the large five-pointed star. The locations of well-studied r-process-rich stars (CS 22892−052, HD 122563, CS 29497−004, CS 31082−001 and RAVE J183013.5−455510) are highlighted by large symbols. Arrow indicate upper limits.

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Yong, D., Kobayashi, C., Da Costa, G.S. et al. r-Process elements from magnetorotational hypernovae. Nature 595, 223–226 (2021).

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