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Extreme 13C,15N and 17O isotopic enrichment in the young planetary nebula K4-47

Naturevolume 564pages378381 (2018) | Download Citation


Carbon, nitrogen and oxygen are the three most abundant elements in the Galaxy after hydrogen and helium. Whereas hydrogen and helium were created in the Big Bang, carbon, nitrogen and oxygen arise from nucleosynthesis in stars. Of particular interest1,2 are the isotopic ratios 12C/13C, 14N/15N and 16O/17O because they are effective tracers of nucleosynthesis and help to benchmark the chemical processes that occurred in primitive interstellar material as it evolved into our Solar System3. However, the origins of the rare isotopes 15N and 17O remain uncertain, although novae and very massive stars that explode as supernovae are postulated4,5,6 to be the main sources of 15N. Here we report millimetre-wavelength observations of the young bipolar planetary nebula K4-47 that indicate another possible source for these isotopes. We identify various carbon-bearing molecules in K4-47 that show that this object is carbon-rich, and find unusually high enrichment in rare carbon (13C), oxygen (17O) and nitrogen (15N) isotopes: 12C/13C = 2.2 ± 0.8, 16O/17O = 21.4 ± 10.3 and 14N/15N = 13.6 ± 6.5 (uncertainties are three standard deviations); for comparison, the corresponding solar ratios7 are 89.4 ± 0.2, 2,632 ± 7 and 435 ± 57. One possible interpretation of these results is that K4-47 arose from a J-type asymptotic giant branch star that underwent a helium-shell flash (an explosive nucleosynthetic event that converts large quantities of helium to carbon and other elements), enriching the resulting planetary nebula in 15N and 17O and creating its bipolar geometry. Other possible explanations are that K4-47 is a binary system or that it resulted from a white dwarf merger, as has been suggested for object CK Vul8. These results suggest that nucleosynthesis of carbon, nitrogen and oxygen is not well understood and that the classification of certain stardust grains must be reconsidered.

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  1. 1.

    Wilson, T. L. & Rood, R. T. Abundances in the interstellar medium. Annu. Rev. Astron. Astrophys. 32, 191–226 (1994).

  2. 2.

    Adande, G. R. & Ziurys, L. M. Millimeter-wave observations of CN and HNC and their 15N isotopologues: a new evaluation of the 14N/15N ratio across the Galaxy. Astrophys. J. 744, 194 (2012).

  3. 3.

    Busemann, H. et al. Interstellar chemistry recorded in organic matter from primitive meteorites. Science 312, 727–730 (2006).

  4. 4.

    José, J. & Hernanz, M. Nucleosynthesis in classical novae: CO versus ONe white dwarfs. Astrophys. J. 494, 680–690 (1998).

  5. 5.

    Pignatari, M. et al. Carbon-rich presolar grains from massive stars: subsolar 12C/13C and 14N/15N ratios and the mystery of 15N. Astrophys. J. 808, L43 (2015).

  6. 6.

    Romano, D., Matteucci, F., Zhang, Z. Y., Papadopoulos, P. P. & Ivison, R. J. The evolution of CNO isotopes: a new window on cosmic star formation history and the stellar IMF in the age of ALMA. Mon. Not. R. Astron. Soc. 470, 401–415 (2017).

  7. 7.

    Asplund, M., Grevesse, N., Sauval, A. J. & Scott, P. The chemical composition of the Sun. Annu. Rev. Astron. Astrophys. 47, 481–522 (2009).

  8. 8.

    Kamiński, T. et al. Organic molecules, ions, and rare isotopologues in the remnant of the stellar-merger candidate, CK Vulpeculae (Nova 1670). Astron. Astrophys. 607, A78 (2017).

  9. 9.

    Corradi, R. et al. High-velocity collimated outflows in planetary nebulae: NGC 6337, He 2–186, and K4–47. Astrophys. J. 535, 823–832 (2000).

  10. 10.

    Akras, S., Gonçalves, D. R. & Ramos-Larios, G. H2 in low-ionization structures of planetary nebulae. Mon. Not. R. Astron. Soc. 465, 1289–1296 (2017).

  11. 11.

    Edwards, J. L., Cox, E. G. & Ziurys, L. M. Millimeter observations of CS, HCO+, and CO toward five planetary nebulae: following molecular abundances with nebular age. Astrophys. J. 791, 79 (2014).

  12. 12.

    van der Tak, F. F. S., Black, J. H., Schöier, F. L., Jansen, D. J. & van Dishoeck, E. F. A computer program for fast non-LTE analysis of interstellar line spectra. Astron. Astrophys. 468, 627–635 (2007).

  13. 13.

    Schmidt, D. R. & Ziurys, L. M. Hidden molecules in planetary nebulae: new detections of HCN and HCO+ from a multi-object survey. Astrophys. J. 817, 175 (2016).

  14. 14.

    Schmidt, D. R. & Ziurys, L. M. New detections of HNC in planetary nebulae: evolution of the [HCN]/[HNC] ratio. Astrophys. J. 835, 79 (2017).

  15. 15.

    Schmidt, D. R. & Ziurys, L. M. New identifications of the CCH radical in planetary nebulae: a connection to C60Astrophys. J. 850, 123 (2017).

  16. 16.

    Redman, M. P., Viti, S., Cau, P. & Williams, D. A. Chemistry and clumpiness in planetary nebulae. Mon. Not. R. Astron. Soc. 345, 1291–1296 (2003).

  17. 17.

    Edwards, J. L. & Ziurys, L. M. Sulfur- and silicon-bearing molecules in planetary nebulae: the case of M2–48. Astrophys. J. 794, L27 (2014).

  18. 18.

    Abia, C., Hedrosa, R. P., Domínguez, I. & Straniero, O. The puzzle of the CNO isotope ratios in asymptotic giant branch carbon stars. Astron. Astrophys. 599, A39 (2017).

  19. 19.

    Harris, M. J., Lambert, D. L., Hinkle, K. H., Gustafsson, B. & Eriksson, K. Oxygen isotopic abundances in evolved stars. III. 26 carbon stars. Astrophys. J. 316, 294–304 (1987).

  20. 20.

    Abia, C. & Isern, J. The chemical composition of carbon stars. II. The J-type stars. Astrophys. J. 536, 438–449 (2000).

  21. 21.

    Milam, S. N., Woolf, N. J. & Ziurys, L. M. Circumstellar 12C/13C isotope ratios from millimeter observations of CN and CO: mixing in carbon- and oxygen-rich stars. Astrophys. J. 690, 837–849 (2009).

  22. 22.

    Hedrosa, R. P. et al. Nitrogen isotopes in asymptotic giant branch carbon stars and presolar SiC grains: a challenge for stellar nucleosynthesis. Astrophys. J. 768, L11 (2013).

  23. 23.

    Wiescher, M., Görres, J., Uberseder, E., Imbriani, G. & Pignatari, M. The cold and hot CNO cycles. Annu. Rev. Nucl. Part. Sci. 60, 381–404 (2010).

  24. 24.

    De Marco, O. The origin and shaping of planetary nebulae: putting the binary hypothesis to the test. Publ. Astron. Soc. Pacif. 121, 316–342 (2009).

  25. 25.

    Kamiński, T. et al. Astronomical detection of radioactive molecule 26AlF in the remnant of an ancient explosion. Nat. Astron. 2, 778–783 (2018).

  26. 26.

    Kamiński, T. et al. Nuclear ashes and outflow in the eruptive star Nova Vul 1670. Nature 520, 322–324 (2015).

  27. 27.

    Gill, C. D. & O’Brien, T. J. Hubble Space Telescope imaging and ground-based spectroscopy of old nova shells – I. FH Ser, V533 Her, BT Mon, DK Lac, and V476 Cyg. Mon. Not. R. Astron. Soc. 314, 175–182 (2000).

  28. 28.

    Lodders, K., & Amari, S. Presolar grains from meteorites: remnants from the early times of the solar system. Chem. Erde–Geochem. 65, 93–166 (2005).

  29. 29.

    Iliadis, C., Downen, L., José, J., Nittler, L. & Starrfield, S. On presolar stardust grains from CO classical novae. Astrophys. J. 855, 76 (2018).

  30. 30.

    Amari, S. et al. Presolar grains from novae. Astrophys. J. 551, 1065–1072 (2001).

  31. 31.

    Schöier, F. L., van der Tak, F. F. S., van Dishoeck, E. F. & Black, J. H. An atomic and molecular database for analysis of submillimetre line observations. Astron. Astrophys. 432, 369–379 (2005).

  32. 32.

    Speck, A. K. et al. Large-scale extended emission around the Helix Nebula: dust, molecules, atoms, and ions. Astron. J. 123, 346–361 (2002).

  33. 33.

    Zeigler, N. R., Zack, L. N., Woolf, N. J. & Ziurys, L. M. The Helix Nebula viewed in HCO+: large-scale mapping of the J = 1→0 transition. Astrophys. J. 778, 16 (2013).

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We thank D. Arnett for insight into stellar evolution modelling and rare-isotope production, including one-dimensional versus three-dimensional simulations. This research was supported by NSF grant AST-1515568 and by NASA under agreement number NNX15AD94G.

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Nature thanks W. Irvine and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information


  1. Department of Astronomy, Steward Observatory, University of Arizona, Tucson, AZ, USA

    • D. R. Schmidt
    • , N. J. Woolf
    •  & L. M. Ziurys
  2. Department of Planetary Science, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA

    • T. J. Zega
  3. Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA

    • L. M. Ziurys
  4. Arizona Radio Observatory, Steward Observatory, University of Arizona, Tucson, AZ, USA

    • L. M. Ziurys


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D.R.S. and L.M.Z. conducted observations of astronomical objects, as well as data reduction and analysis. N.J.W. and T.J.Z. helped in the scientific interpretation of the data with regard to stellar evolution and presolar grains studies, respectively. All authors wrote the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to L. M. Ziurys.

Extended data figures and tables

  1. Extended Data Table 1 Line parameters for observed molecules

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