Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Revised rates for the stellar triple-α process from measurement of 12C nuclear resonances


In the centres of stars where the temperature is high enough, three α-particles (helium nuclei) are able to combine to form 12C because of a resonant reaction leading to a nuclear excited state1. (Stars with masses greater than 0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed.) Although the reaction rate is of critical significance for determining elemental abundances in the Universe1, and for determining the size of the iron core of a star just before it goes supernova2, it has hitherto been insufficiently determined2. Here we report a measurement of the inverse process, where a 12C nucleus decays to three α-particles. We find a dominant resonance at an energy of 11 MeV, but do not confirm the presence of a resonance at 9.1 MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-α rate for temperatures from 107 K to 1010 K and find significant deviations from the standard rates3. Our rate below 5 × 107 K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed4. At temperatures above 109 K, our rate is much less, which modifies predicted nucleosynthesis in supernovae5,6.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: α-particles emitted from resonances in 12C populated in the decays of 12B and 12N.
Figure 2: Excitation energy spectra in 12C.
Figure 3: The triple-α reaction rate from this work, r, relative to the value from the current NACRE compilation3, r(NACRE).

Similar content being viewed by others


  1. Wallerstein, G. et al. Synthesis of the elements in stars: 40 years of progress. Rev. Mod. Phys. 69, 995–1084 (1997)

    Article  ADS  CAS  Google Scholar 

  2. Austin, S. in Proc. 8th Nuclei in the Cosmos Conf., Nucl. Phys. A (in the press)

  3. Angulo, C. et al. A compilation of charged-particle induced thermonuclear reaction rates. Nucl. Phys. A 656, 3–183 (1999)

    Article  ADS  Google Scholar 

  4. Siess, L., Livio, M. & Lattanzio, J. Structure, evolution, and nucleosynthesis of primordial stars. Astrophys. J. 570, 329–343 (2002)

    Article  ADS  CAS  Google Scholar 

  5. Fröhlich, C. et al. Composition of the innermost supernova ejecta. Astrophys. J. (submitted)

  6. Pruet, J., Woosley, S. E., Buras, R., Janka, H.-T. & Hofmann, R. D. Nucleosynthesis in the hot convective bubble in core-collapse supernovae. Astrophys. J. (submitted)

  7. Ajzenberg-Selove, F. Energy levels of light nuclei A = 11–12. Nucl. Phys. A 506, 1–158 (1990)

    Article  ADS  Google Scholar 

  8. Hoyle, F., Dunbar, D. N. F., Wenzel, W. A. & Whaling, W. A state in 12C predicted from astrophysical evidence. Phys. Rev. 92, 1095 (1953)

    CAS  Google Scholar 

  9. Dunbar, D. N. F., Pixley, R. E., Wenzel, W. A. & Whaling, W. The 7.68 MeV state in 12C. Phys. Rev. 92, 649–650 (1953)

    Article  ADS  CAS  Google Scholar 

  10. Cook, C. W., Fowler, W. A., Lauritsen, C. C. & Lauritsen, T. B12, C12, and the red giants. Phys. Rev. 107, 508–515 (1957)

    Article  ADS  CAS  Google Scholar 

  11. Morinaga, H. Interpretation of some of the excited states of 4n self-conjugate nuclei. Phys. Rev. 101, 254–258 (1956)

    Article  ADS  CAS  Google Scholar 

  12. Cook, C. W., Fowler, W. A., Lauritsen, C. C. & Lauritsen, T. High energy alpha particles from B12 . Phys. Rev. 111, 567–571 (1958)

    Article  ADS  CAS  Google Scholar 

  13. Fynbo, H. O. U. et al. Clarification of the three-body decay of 12C(12.71 MeV). Phys. Rev. Lett. 91, 082502 (2003)

    Article  ADS  CAS  Google Scholar 

  14. Lane, A. M. & Thomas, R. G. R-matrix theory of nuclear reactions. Rev. Mod. Phys. 30, 257–353 (1958)

    Article  ADS  MathSciNet  Google Scholar 

  15. John, B., Tokimoto, Y., Lui, Y.-W., Clark, H. L., Chen, X. & Youngblood, D. H. Isoscalar electric multipole strength in 12C. Phys. Rev. C 68, 014305 (2003)

    Article  ADS  Google Scholar 

  16. Itoh, M. et al. Study of the cluster state at Ex = 10.3 MeV in 12C. Nucl. Phys. A 738, 268–272 (2004)

    Article  ADS  Google Scholar 

  17. Fowler, W. A. Experimental and theoretical nuclear astrophysics: The quest for the origin of the elements. Rev. Mod. Phys. 56, 149–179 (1984)

    Article  ADS  CAS  Google Scholar 

  18. Weaver, T. A. & Woosley, S. E. Nucleosynthesis in massive stars and the 12C(α,γ)16O reaction rate. Phys. Rep. 227, 65–96 (1993)

    Article  ADS  CAS  Google Scholar 

  19. Schlattl, H., Heger, A., Oberhummer, H., Rauscher, T. & Csótó, A. Sensitivity of the C and O production on the 3α rate. Astrophys. Space Sci. 291, 27–56 (2004)

    Article  ADS  CAS  Google Scholar 

  20. Delano, M. D. & Cameron, A. G. W. Nucleosynthesis in neutron rich supernova ejecta. Astrophys. Space Sci. 10, 203–226 (1971)

    Article  ADS  CAS  Google Scholar 

  21. Schatz, H. et al. Rp-process nucleosynthesis at extreme temperature and density conditions. Phys. Rep. 294, 167–263 (1998)

    Article  ADS  CAS  Google Scholar 

  22. Woosley, S. E. et al. Models for Type I X-ray bursts with improved nuclear physics. Astrophys. J. Supp. 151, 75–102 (2004)

    Article  ADS  CAS  Google Scholar 

  23. Käppeler, F., Thielemann, F.-K. & Wiescher, M. Current quests in nuclear astrophysics and experimental approaches. Annu. Rev. Part. Sci. 48, 175–251 (1998)

    Article  ADS  Google Scholar 

  24. Herwig, F. & Austin, S. M. Nuclear reaction rates and carbon star formation. Astrophys. J. 613, L73–L76 (2004)

    Article  ADS  CAS  Google Scholar 

  25. Äystö, J. Development and applications of the IGISOL technique. Nucl. Phys. A 693, 477–494 (2001)

    Article  ADS  Google Scholar 

  26. Kugler, E. The ISOLDE facility. Hyperfine Interact. 129, 23–42 (2000)

    Article  ADS  CAS  Google Scholar 

  27. Bergmann, U. C., Fynbo, H. O. U. & Tengblad, O. Use of Si strip detectors for low-energy particles in compact geometry. Nucl. Instrum. Methods A 515, 657–664 (2003)

    Article  ADS  CAS  Google Scholar 

  28. Tengblad, O., Bergmann, U. C., Fraile, L. M., Fynbo, H. O. U. & Walsh, S. Novel thin window design for a large-area silicon strip detector. Nucl. Instrum. Methods A 525, 458–464 (2004)

    Article  ADS  CAS  Google Scholar 

  29. Barker, F. C. & Warburton, E. K. The beta-decay of 8He. Nucl. Phys. A 487, 269–278 (1988)

    Article  ADS  Google Scholar 

  30. Schwalm, D. & Povh, B. Alpha particles following the β-decay of 12B and 12N. Nucl. Phys. 89, 401–411 (1966)

    Article  CAS  Google Scholar 

Download references


This research was supported by the Academy of Finland under the Finnish Centre of Excellence Programme, by the Spanish Agency CICYT, and by the European Union Fifth Framework Programme ‘Improving Human Potential—Access to Research Infrastructure’. Discussions with J. Christensen-Dalsgaard and C. Fröhlich are acknowledged.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Hans O. U. Fynbo.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Fynbo, H., Diget, C., Bergmann, U. et al. Revised rates for the stellar triple-α process from measurement of 12C nuclear resonances. Nature 433, 136–139 (2005).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing