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.

Magnetic fields of 30 to 100 kG in the cores of red giant stars


A red giant star is an evolved low- or intermediate-mass star that has exhausted its central hydrogen content, leaving a helium core and a hydrogen-burning shell. Oscillations of stars can be observed as periodic dimmings and brightenings in the optical light curves. In red giant stars, non-radial acoustic waves couple to gravity waves and give rise to mixed modes, which behave as pressure modes in the envelope and gravity modes in the core. These modes have previously been used to measure the internal rotation of red giants1,2, leading to the conclusion that purely hydrodynamical processes of angular momentum transport from the core are too inefficient3. Magnetic fields could produce the additional required transport4,5,6. However, owing to the lack of direct measurements of magnetic fields in stellar interiors, little is currently known about their properties. Asteroseismology can provide direct detection of magnetic fields because, like rotation, the fields induce shifts in the oscillation mode frequencies7,8,9,10,11,12. Here we report the measurement of magnetic fields in the cores of three red giant stars observed with the Kepler13 satellite. The fields induce shifts that break the symmetry of dipole mode multiplets. We thus measure field strengths ranging from about 30 kilogauss to about 100 kilogauss in the vicinity of the hydrogen-burning shell and place constraints on the field topology.

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

Access options

Rent or buy this article

Get just this article for as long as you need it


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

Fig. 1: Asymmetric splittings of two mixed modes in KIC 8684542.
Fig. 2: Multiplet asymmetries in KIC 8684542 as a function of mode frequency.
Fig. 3: Stretched échelle diagram for KIC 8684542.

Data availability

Kepler data are publicly available from the Mikulski Archive for Space Telescopes (MAST) portal at Spectra are available at

Code availability

This study makes use of the stellar evolution code MESA, which is available at


  1. Deheuvels, S. et al. Seismic evidence for a rapidly rotating core in a lower-giant-branch star observed with Kepler. Astrophys. J. 756, 19 (2012).

    Article  ADS  Google Scholar 

  2. Gehan, C., Mosser, B., Michel, E., Samadi, R. & Kallinger, T. Core rotation braking on the red giant branch for various mass ranges. Astron. Astrophys. 616, A24 (2018).

    Article  ADS  Google Scholar 

  3. Marques, J. P. et al. Seismic diagnostics for transport of angular momentum in stars. I. Rotational splittings from the pre-main sequence to the red-giant branch. Astron. Astrophys. 549, A74 (2013).

    Article  Google Scholar 

  4. Gough, D. O. & McIntyre, M. E. Inevitability of a magnetic field in the Sun’s radiative interior. Nature 394, 755–757 (1998).

    Article  ADS  CAS  Google Scholar 

  5. Fuller, J., Piro, A. L. & Jermyn, A. S. Slowing the spins of stellar cores. Mon. Not. R. Astron. Soc. 485, 3661–3680 (2019).

    Article  ADS  CAS  Google Scholar 

  6. Gouhier, B., Jouve, L. & Lignières, F. Angular momentum transport in a contracting stellar radiative zone embedded in a large scale magnetic field. Astron. Astrophys. 661, A119 (2022).

  7. Unno, W., Osaki, Y., Ando, H., Saio, H. & Shibahashi, H. Nonradial Oscillations of Stars (Univ. Tokyo Press, 1989).

  8. Gough, D. O. & Thompson, M. J. The effect of rotation and a buried magnetic field on stellar oscillations. Mon. Not. R. Astron. Soc. 242, 25–55 (1990).

    Article  ADS  Google Scholar 

  9. Hasan, S. S., Zahn, J. P. & Christensen-Dalsgaard, J. Probing the internal magnetic field of slowly pulsating B-stars through g modes. Astron. Astrophys. 444, L29–L32 (2005).

    Article  ADS  Google Scholar 

  10. Gomes, P. & Lopes, I. Core magnetic field imprint in the non-radial oscillations of red giant stars. Mon. Not. R. Astron. Soc. 496, 620–628 (2020).

    Article  ADS  CAS  Google Scholar 

  11. Bugnet, L. et al. Magnetic signatures on mixed-mode frequencies. I. An axisymmetric fossil field inside the core of red giants. Astron. Astrophys. 650, A53 (2021).

    Article  Google Scholar 

  12. Loi, S. T. Topology and obliquity of core magnetic fields in shaping seismic properties of slowly rotating evolved stars. Mon. Not. R. Astron. Soc. 504, 3711–3729 (2021).

    Article  ADS  Google Scholar 

  13. Borucki, W. J. et al. Kepler planet-detection mission: introduction and first results. Science 327, 977–980 (2010).

    Article  ADS  CAS  Google Scholar 

  14. Mathis, S. et al. Probing the internal magnetism of stars using asymptotic magneto-asteroseismology. Astron. Astrophys. 647, A122 (2021).

    Article  Google Scholar 

  15. Deheuvels, S., Ouazzani, R. M. & Basu, S. Near-degeneracy effects on the frequencies of rotationally-split mixed modes in red giants. Astron. Astrophys. 605, A75 (2017).

    Article  ADS  Google Scholar 

  16. Dziembowski, W. A. & Goode, P. R. Effects of differential rotation on stellar oscillations: a second-order theory. Astrophys. J. 394, 670 (1992).

    Article  ADS  Google Scholar 

  17. Paxton, B. et al. Modules for Experiments in Stellar Astrophysics (MESA). Astrophys. J. Suppl. Ser. 192, 3 (2011).

    Article  ADS  Google Scholar 

  18. Mosser, B. et al. Period spacings in red giants. IV. Toward a complete description of the mixed-mode pattern. Astron. Astrophys. 618, A109 (2018).

    Article  Google Scholar 

  19. Takata, M. Asymptotic analysis of dipolar mixed modes of oscillations in red giant stars. Publ. Astron. Soc. Jpn 68, 109 (2016).

    Article  ADS  Google Scholar 

  20. Fuller, J., Cantiello, M., Stello, D., Garcia, R. A. & Bildsten, L. Asteroseismology can reveal strong internal magnetic fields in red giant stars. Science 350, 423–426 (2015).

    Article  ADS  MathSciNet  CAS  Google Scholar 

  21. Stello, D. et al. A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass stars. Nature 529, 364–367 (2016).

    Article  ADS  CAS  Google Scholar 

  22. Donati, J. F. & Landstreet, J. D. Magnetic fields of nondegenerate stars. Annu. Rev. Astron. Astrophys. 47, 333–370 (2009).

    Article  ADS  CAS  Google Scholar 

  23. Braithwaite, J. & Spruit, H. C. Magnetic fields in non-convective regions of stars. R. Soc. Open Sci. 4, 160271 (2017).

    Article  ADS  MathSciNet  Google Scholar 

  24. Becerra, L., Reisenegger, A., Valdivia, J. A. & Gusakov, M. E. Evolution of random initial magnetic fields in stably stratified and barotropic stars. Mon. Not. R. Astron. Soc. 511, 732–745 (2022).

    Article  ADS  Google Scholar 

  25. Cantiello, M., Fuller, J. & Bildsten, L. Asteroseismic signatures of evolving internal stellar magnetic fields. Astrophys. J. 824, 14 (2016).

    Article  ADS  Google Scholar 

  26. Brun, A. S., Browning, M. K. & Toomre, J. Simulations of core convection in rotating A-type stars: magnetic dynamo action. Astrophys. J. 629, 461–481 (2005).

    Article  ADS  Google Scholar 

  27. Aurière, M. et al. Weak magnetic fields in Ap/Bp stars. Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomy. Astron. Astrophys. 475, 1053–1065 (2007).

    Article  ADS  Google Scholar 

  28. Deheuvels, S. et al. Seismic constraints on the radial dependence of the internal rotation profiles of six Kepler subgiants and young red giants. Astron. Astrophys. 564, A27 (2014).

    Article  Google Scholar 

  29. Mosser, B., Vrard, M., Belkacem, K., Deheuvels, S. & Goupil, M. J. Period spacings in red giants. I. Disentangling rotation and revealing core structure discontinuities. Astron. Astrophys. 584, A50 (2015).

    Article  ADS  Google Scholar 

Download references


We acknowledge support from from the project BEAMING ANR-18-CE31-0001 of the French National Research Agency (ANR) and from the Centre National d’Etudes Spatiales (CNES).

Author information

Authors and Affiliations



G.L. discovered the three stars with asymmetric splittings. G.L. and S.D. measured the asymmetries and rotation rates. S.D. measured the absolute magnetic shifts and supervised the whole project. J.B. and F.L. developed the theoretical framework used to interpret the observations. All the authors contributed to writing the manuscript.

Corresponding author

Correspondence to Sébastien Deheuvels.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature thanks Matteo Cantiello, Margarida Cunha and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Additional information

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 Shape of the weight function K(m) as a function of the normalized mass.

The function K(m) is shown for the stellar model representative of KIC 11515377. The blue shaded region indicates the hydrogen-burning shell. The vertical dashed line corresponds to the maximal extent of the initial convective core at the beginning of the main sequence.

Extended Data Fig. 2 Multiplet asymmetries in KIC 11515377 as a function of mode frequency.

Symbols have the same meaning as in Fig. 2.

Extended Data Fig. 3 Multiplet asymmetries in KIC 7518143 as a function of mode frequency.

Symbols have the same meaning as in Fig. 2.

Extended Data Fig. 4 Stretched échelle diagram for KIC 11515377.

Symbols have the same meaning as in Fig. 3.

Extended Data Fig. 5 Stretched échelle diagram for KIC 7518143.

Symbols have the same meaning as in Fig. 3.

Supplementary information

Supplementary Information

Supplementary Sections 1–7, including Supplementary Figs. 1–6 and Tables 1–7.

Peer Review File

Rights and permissions

Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Li, G., Deheuvels, S., Ballot, J. et al. Magnetic fields of 30 to 100 kG in the cores of red giant stars. Nature 610, 43–46 (2022).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


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