It is difficult to establish the properties of massive stars that explode as supernovae1,2. The electromagnetic emission during the first minutes to hours after the emergence of the shock from the stellar surface conveys important information about the final evolution and structure of the exploding star3,4,5,6. However, the unpredictable nature of supernova events hinders the detection of this brief initial phase7,8,9. Here we report the serendipitous discovery of a newly born, normal type IIb supernova (SN 2016gkg)10, which reveals a rapid brightening at optical wavelengths of about 40 magnitudes per day. The very frequent sampling of the observations allowed us to study in detail the outermost structure of the progenitor of the supernova and the physics of the emergence of the shock. We develop hydrodynamical models of the explosion that naturally account for the complete evolution of the supernova over distinct phases regulated by different physical processes. This result suggests that it is appropriate to decouple the treatment of the shock propagation from the unknown mechanism that triggers the explosion.

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We are grateful to P. Brown for providing information about the photometry of the early Swift/UVOT data of SN 2006aj. M.C.B. acknowledges support from the Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) through grant PICT-2015-3083 ‘Progenitores de Supernovas de Colapso Gravitatorio’ and from the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence ‘Origin and Structure of the Universe’. M.C.B., G.F. and O.G.B. acknowledge support from grant PIP-2015-2017-11220150100746CO of CONICET ‘Estrellas Binarias y Supernovas’. G.F. further acknowledges support from ANPCyT grant PICT-2015-2734 ‘Nacimiento y Muerte de Estrellas Masivas: Su relación con el Medio Interestelar’. K.M. acknowledges support from JSPS KAKENHI grant 17H02864. Partial support for this work was provided by NASA through programmes GO-14115 and AR-14295 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. M.O. acknowledges support from grant PI UNRN40B531. A.V.F. is also grateful for financial assistance from the Christopher R. Redlich Fund, the TABASGO Foundation and the Miller Institute for Basic Research in Science (University of California Berkeley). We thank the University of California Berkeley undergraduate students S. Channa, G. Halevy, A. Halle, M. de Kouchkovsky, J. Molloy, T. Ross, S. Stegman and S. Yunus for their effort in collecting Lick/Nickel data, and T.d.J. for help with some of the Keck observations. The Lick and Keck Observatory staff provided excellent assistance. A major upgrade of the Kast spectrograph on the Shane 3-m telescope at Lick Observatory was made possible through gifts from William and Marina Kast as well as the Heising-Simons Foundation. Research at Lick Observatory is partially supported by a gift from Google. KAIT and its on-going operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia and Jim Katzman Foundation and the TABASGO Foundation. Some of the data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among California Institute of Technology, the University of California and NASA; the observatory was made possible by financial support from the W. M. Keck Foundation. O.G.B. is a member of the Carrera del Investigador Científico de la Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC), Argentina.

Author information


  1. Instituto de Astrofísica de La Plata (IALP), CONICET, Argentina

    • M. C. Bersten
    • , G. Folatelli
    •  & O. G. Benvenuto
  2. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA, La Plata, Argentina

    • M. C. Bersten
    • , G. Folatelli
    • , F. García
    •  & O. G. Benvenuto
  3. Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan

    • M. C. Bersten
    • , G. Folatelli
    • , K. Maeda
    •  & K. Nomoto
  4. Instituto Argentino de Radioastronomía (CCT-La Plata, CONICET; CICPBA), CC No. 5, 1894 Villa Elisa, Argentina.

    • F. García
  5. Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, F-91191 Gif-sur-Yvette, France

    • F. García
  6. Caltech/IPAC, Mailcode 100-22, Pasadena, California 91125, USA

    • S. D. Van Dyk
  7. Sede Andina, Universidad Nacional de Río Negro, Mitre 630 (8400) Bariloche, CONICET, Argentina

    • M. Orellana
  8. Observatorio Astronómico Busoniano, Entre Ríos 2974 (2000), Rosario, Argentina

    • V. Buso
  9. Observatorio Astronómico Geminis Austral, Rosario, Argentina.

    • J. L. Sánchez
  10. Division of Theoretical Astronomy, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

    • M. Tanaka
    •  & T. J. Moriya
  11. Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan

    • K. Maeda
  12. Department of Astronomy, University of California, Berkeley, California 94720-3411, USA

    • A. V. Filippenko
    • , W. Zheng
    • , T. G. Brink
    • , T. de Jaeger
    •  & I. Shivvers
  13. Miller Senior Fellow, Miller Institute for Basic Research in Science, University of California, Berkeley, California 94720, USA

    • A. V. Filippenko
  14. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

    • S. B. Cenko
  15. Joint Space-Science Institute, University of Maryland, College Park, Maryland 20742, USA

    • S. B. Cenko
  16. Department of Physics, Florida State University, 77 Chieftain Way, Tallahassee, Florida 32306, USA.

    • S. Kumar
  17. Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK

    • D. A. Perley
  18. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.

    • N. Smith


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M.C.B., hydrodynamical models and interpretation. G.F., supernova and pre-supernova data analysis and interpretation. F.G., supernova data analysis and interpretation. S.V.D.D., supernova and pre-supernova data analysis and interpretation. O.G.B., binary evolution models. M.O., early data comparisons. M.T. and K.M., shock-breakout interpretation. V.B., supernova discovery. J.L.S., early supernova observations. A.V.F., Lick and Keck Observatory data and paper editing. W.Z., T.G.B., T.d.J., I.S., S.K. and N.S., observations and reductions. T.J.M., circumstellar material interpretation. K.N., pre-supernova models. S.B.C. and D.A.P., spectral reductions.

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The authors declare no competing financial interests.

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Correspondence to M. C. Bersten or G. Folatelli.

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