Skip to main content

Thank you for visiting nature.com. 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.

  • Article
  • Published:

Chemical evolution imprints in the rare isotopes of nearby M dwarfs

Nature Astronomy (2025)Cite this article

Subjects

Abstract

Elements heavier than hydrogen and helium, collectively termed metals, were created inside stars and dispersed through space at the final stages of stellar evolution. The relative amounts of different isotopes (variants of the same element with different masses) in stellar atmospheres provide clues about how our galaxy evolved chemically over billions of years. M dwarfs are small, cool, long-lived stars that comprise three-quarters of all stars in our galaxy. Their spectra exhibit rich fingerprints of their composition, making them potential tracers of chemical evolution. Here we measure rare carbon and oxygen isotopes in 32 nearby M dwarfs spanning a range of metallicities using high-resolution infrared spectroscopy. We find that stars with higher metal content have lower 12C/13C ratios, indicating they formed from material progressively enriched in 13C over time. This pattern is consistent with models where novae eruptions contributed significant amounts of 13C to the interstellar medium over the past few billion years. Our measurements of the 16O/18O ratio align with theoretical predictions and indicate that metal-rich stars attain significantly lower 16O/18O ratios than the Sun. These results establish M dwarfs as tracers of chemical evolution throughout cosmic history.

Access through your institution
Buy or subscribe

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

Access options

Access through your institution

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

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

Fig. 1: Spectra of all targets in the sample.
Fig. 2: Isotopologue detection validation.
Fig. 3: Isotope ratios in M dwarf atmospheres.
Fig. 4: The M dwarf opportunity for GCE.

Similar content being viewed by others

Data availability

The reduced SPIRou data are available via the Canadian Astronomy Data Center (CADC) at https://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/. The reduced data used in this work and the derived best-fit model spectra are publicly available via Zenodo at https://doi.org/10.5281/zenodo.15828872 (ref. 65).

Code availability

The software to calculate the cross-sections used in this work is available via GitHub at https://github.com/samderegt/pyROX. The radiative transfer code to generate atmospheric models is available at https://petitradtrans.readthedocs.io/en/2.7.7/. The equilibrium chemistry code FastChem is available via GitHub at https://github.com/NewStrangeWorlds/FastChem. The implementation of the Nested Sampling algorithm used in this work is available via GitHub at https://github.com/JohannesBuchner/PyMultiNest.

References

  1. Henry, T. J., Kirkpatrick, J. D. & Simons, D. A. The Solar Neighborhood. I. Standard spectral types (K5–M8) for northern dwarfs within eight parsecs. Astron. J. 108, 1437 (1994).

    Article  ADS  Google Scholar 

  2. Reylé, C. et al. The 10 parsec sample in the Gaia era. Astron. Astrophys. 650, A201 (2021).

    Article  Google Scholar 

  3. Hayashi, C. & Nakano, T. Evolution of stars of small masses in the pre-main-sequence stages. Prog. Theor. Phys. 30, 460–474 (1963).

    Article  ADS  Google Scholar 

  4. Tsuji, T. Near-infrared spectroscopy of M dwarfs. IV. A preliminary survey on the carbon isotopic ratio in M dwarfs. Publ. Astron. Soc. Jpn 68, 84 (2016).

    Article  ADS  Google Scholar 

  5. Zhang, Y. et al. 13CO-rich atmosphere of a young accreting super-Jupiter. Nature 595, 370–372 (2021).

    Article  ADS  Google Scholar 

  6. Xuan, J. W. et al. Validation of elemental and isotopic abundances in late-M spectral types with the benchmark HIP 55507 AB system. Astrophys. J. 962, 10 (2024).

    Article  ADS  Google Scholar 

  7. Botelho, R. B. et al. Carbon, isotopic ratio 12C/13C, and nitrogen in solar twins: constraints for the chemical evolution of the local disc. Mon. Not. R. Astron. Soc. 499, 2196–2213 (2020).

    Article  ADS  Google Scholar 

  8. Crossfield, I. J. M. et al. Unusual isotopic abundances in a fully convective stellar binary. Astrophys. J. 871, L3 (2019).

    Article  ADS  Google Scholar 

  9. Prantzos, N., Aubert, O. & Audouze, J. Evolution of the carbon and oxygen isotopes in the Galaxy. Astron. Astrophys. 309, 760–774 (1996).

    ADS  Google Scholar 

  10. Romano, D. & Matteucci, F. Nova nucleosynthesis and galactic evolution of the CNO isotopes. Mon. Not. R. Astron. Soc. 342, 185–198 (2003).

    Article  ADS  Google Scholar 

  11. Zhang, Z.-Y., Romano, D., Ivison, R. J., Papadopoulos, P. P. & Matteucci, F. Stellar populations dominated by massive stars in dusty starburst galaxies across cosmic time. Nature 558, 260–263 (2018).

    Article  ADS  Google Scholar 

  12. Romano, D. The evolution of CNO elements in galaxies. Astron. Astrophys. Rev. 30, 7 (2022).

    Article  ADS  Google Scholar 

  13. Donati, J.-F. et al. SPIRou: NIR velocimetry and spectropolarimetry at the CFHT. Mon. Not. R. Astron. Soc. 498, 5684–5703 (2020).

    Article  ADS  Google Scholar 

  14. Cristofari, P. I. et al. Measuring small-scale magnetic fields of 44 M dwarfs from SPIRou spectra with ZeeTurbo. Mon. Not. R. Astron. Soc. 526, 5648–5674 (2023).

    Article  ADS  Google Scholar 

  15. Engle, S. G. & Guinan, E. F. Living with a red dwarf: the rotation–age relationships of M dwarfs. Astrophys. J. Lett. 954, L50 (2023).

    Article  ADS  Google Scholar 

  16. Romano, D. et al. The Gaia-ESO survey: galactic evolution of lithium from iDR6. Astron. Astrophys. 653, A72 (2021).

    Article  Google Scholar 

  17. Cristofari, P. I. et al. Estimating fundamental parameters of nearby M dwarfs from SPIRou spectra. Mon. Not. R. Astron. Soc. 511, 1893–1912 (2022).

    Article  ADS  Google Scholar 

  18. Mollière, P. et al. petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval. Astron. Astrophys. 627, A67 (2019).

    Article  Google Scholar 

  19. Kitzmann, D., Stock, J. W. & Patzer, A. B. C. FASTCHEM COND: equilibrium chemistry with condensation and rainout for cool planetary and stellar environments. Mon. Not. R. Astron. Soc. 527, 7263–7283 (2023).

    Article  ADS  Google Scholar 

  20. Kobayashi, C., Karakas, A. I. & Umeda, H. The evolution of isotope ratios in the Milky Way Galaxy. Mon. Not. R. Astron. Soc. 414, 3231–3250 (2011).

    Article  ADS  Google Scholar 

  21. Nomoto, K., Kobayashi, C. & Tominaga, N. Nucleosynthesis in stars and the chemical enrichment of galaxies. Ann. Rev. Astron. Astrophys. 51, 457–509 (2013).

    Article  ADS  Google Scholar 

  22. Renzini, A. & Voli, M. Advanced evolutionary stages of intermediate-mass stars. I – Evolution of surface compositions. Astron. Astrophys. 94, 175 (1981).

    ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  24. Karakas, A. I. & Lattanzio, J. C. The Dawes Review 2: nucleosynthesis and stellar yields of low- and intermediate-mass single stars. Publ. Astron. Soc. Aust. 31, e030 (2014).

    Article  ADS  Google Scholar 

  25. Hirschi, R. Very low-metallicity massive stars: pre-SN evolution models and primary nitrogen production. Astron. Astrophys. 461, 571–583 (2007).

    Article  ADS  Google Scholar 

  26. Limongi, M. & Chieffi, A. Presupernova evolution and explosive nucleosynthesis of rotating massive stars in the metallicity range −3 ≤ [Fe/H] ≤ 0. Astrophys. J. Suppl. 237, 13 (2018).

    Article  ADS  Google Scholar 

  27. Romano, D., Karakas, A. I., Tosi, M. & Matteucci, F. Quantifying the uncertainties of chemical evolution studies – II. Stellar yields. Astron. Astrophys. 522, A32 (2010).

    Article  ADS  Google Scholar 

  28. Meynet, G., Ekström, S. & Maeder, A. The early star generations: the dominant effect of rotation on the CNO yields. Astron. Astrophys. 447, 623–639 (2006).

    Article  ADS  Google Scholar 

  29. Chiappini, C. et al. A new imprint of fast rotators: low 12C/13C ratios in extremely metal-poor halo stars. Astron. Astrophys. 479, L9–L12 (2008).

    Article  ADS  Google Scholar 

  30. Spite, M., Spite, F. & Barbuy, B. 12C/13C ratio and CNO abundances in the classical very old metal-poor dwarf HD 140283. Astron. Astrophys. 652, A97 (2021).

    Article  ADS  Google Scholar 

  31. Milam, S. N., Savage, C., Brewster, M. A., Ziurys, L. M. & Wyckoff, S. The 12C/13C isotope gradient derived from millimeter transitions of CN: the case for galactic chemical evolution. Astrophys. J. 634, 1126��1132 (2005).

    Article  ADS  Google Scholar 

  32. Kubryk, M., Prantzos, N. & Athanassoula, E. Radial migration in a bar-dominated disc galaxy – I. Impact on chemical evolution. Mon. Not. R. Astron. Soc. 436, 1479–1491 (2013).

    Article  ADS  Google Scholar 

  33. Fuhrmann, K., Chini, R., Kaderhandt, L. & Chen, Z. On the local stellar populations. Mon. Not. R. Astron. Soc. 464, 2610–2621 (2017).

    Article  ADS  Google Scholar 

  34. Mann, A. W., Feiden, G. A., Gaidos, E. & Boyajian, T. How to constrain your M dwarf: measuring effective temperature, bolometric luminosity, mass, and radius. Astrophys. J. 804, 64 (2015).

    Article  ADS  Google Scholar 

  35. Heger, A. & Woosley, S. E. The nucleosynthetic signature of population III. Astrophys. J. 567, 532–543 (2002).

    Article  ADS  Google Scholar 

  36. Wilson, T. L. Isotopes in the interstellar medium and circumstellar envelopes. Rep. Prog. Phys. 62, 143 (1999).

    Article  ADS  Google Scholar 

  37. Ayres, T. R., Lyons, J. R., Ludwig, H.-G., Caffau, E. & Wedemeyer-Böhm, S. Is the Sun lighter than the Earth? Isotopic CO in the photosphere, viewed through the lens of three-dimensional spectrum synthesis. Astrophys. J. 765, 46 (2013).

    Article  ADS  Google Scholar 

  38. Molaro, P. et al. The 12C/13C isotopic ratio at the dawn of chemical evolution. Astron. Astrophys. 679, A72 (2023).

    Article  Google Scholar 

  39. Ryan, S. G., Aoki, W., Norris, J. E. & Beers, T. C. The origins of two classes of carbon-enhanced, metal-poor stars. Astrophys. J. 635, 349 (2005).

    Article  ADS  Google Scholar 

  40. Brandl, B. et al. METIS: the Mid-infrared ELT Imager and Spectrograph. The Messenger 182, 22–26 (2021).

    ADS  Google Scholar 

  41. Jakobsen, P. et al. The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope: I. Overview of the instrument and its capabilities. Astron. Astrophys. 661, A80 (2022).

    Article  Google Scholar 

  42. Gardner, J. P. et al. The James Webb Space Telescope. Space Sci. Rev. 123, 485–606 (2006).

    Article  ADS  Google Scholar 

  43. Cristofari, P. I. et al. Estimating the atmospheric properties of 44 M dwarfs from SPIRou spectra. Mon. Not. R. Astron. Soc. 516, 3802–3820 (2022).

    Article  ADS  Google Scholar 

  44. Cristofari, P. I. et al. Constraining atmospheric parameters and surface magnetic fields with ZeeTurbo: an application to SPIRou spectra. Mon. Not. R. Astron. Soc. 522, 1342–1357 (2023).

    Article  ADS  Google Scholar 

  45. Cook, N. J. et al. APERO: A PipelinE to Reduce Observations—demonstration with SPIRou. Publ. Astron. Soc. Pac. 134, 114509 (2022).

    Article  ADS  Google Scholar 

  46. Tennyson, J. et al. The 2024 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres. J. Quant. Spectrosc. Radiat. Transf. 326, 109083 (2024).

    Article  Google Scholar 

  47. Rothman, L. S. et al. HITEMP, the high-temperature molecular spectroscopic database. J. Quant. Spectrosc. Radiat. Transf. 111, 2139–2150 (2010).

    Article  ADS  Google Scholar 

  48. Kurucz, R. L. in Stellar Atmospheres: Beyond Classical Models NATO ASI Series (eds Crivellari, L. et al.) 441–448 (Springer, 1991).

  49. Kramida, A., Ralchenko, Yu., Reader, J. & NIST ASD Team. NIST Atomic Spectra Database (version 5.12) (National Institute of Standards and Technology, 2024); https://doi.org/10.18434/T4W30F

  50. Zhang, Y. et al. Elemental abundances of the super-Neptune WASP-107b from Hubble and Spitzer photometry. Astron. J. 165, 62 (2023).

    Article  ADS  Google Scholar 

  51. González Picos, D. et al. The ESO SupJup Survey – II. The 12C/13C isotope ratios of three young brown dwarfs with CRIRES+. Astron. Astrophys. 689, A212 (2024).

    Article  Google Scholar 

  52. Czesla, S. et al. PyA: Python astronomy-related packages (Astrophysics Source Code Library, 2019).

  53. Husser, T.-O. et al. A new extensive library of PHOENIX stellar atmospheres and synthetic spectra. Astron. Astrophys. 553, A6 (2013).

    Article  Google Scholar 

  54. Grant, D. & Wakeford, H. ExoTiC-LD: thirty seconds to stellar limb-darkening coefficients. J. Open Source Softw. 9, 6816 (2024).

    Article  Google Scholar 

  55. Hauschildt, P. H., Allard, F. & Baron, E. The NextGen model atmosphere grid for 3000 ≤ Teff ≤ 10,000 K. Astrophys. J. 512, 377 (1999).

    Article  ADS  Google Scholar 

  56. Hahlin, A. et al. Multi-scale magnetic field investigation of the M-dwarf eclipsing binary CU Cancri. Astron. Astrophys. 684, A175 (2024).

    Article  Google Scholar 

  57. Ruffio, J.-B. et al. Detecting exomoons from radial velocity measurements of self-luminous planets: application to observations of HR 7672 B and future prospects. Astron. J. 165, 113 (2023).

    Article  ADS  Google Scholar 

  58. Feroz, F., Hobson, M. P., Cameron, E. & Pettitt, A. N. Importance nested sampling and the MultiNest Algorithm. Open J. Astrophys. 2, 10 (2019).

    Google Scholar 

  59. Buchner, J. PyMultiNest: Python interface for MultiNest (Astrophysics Source Code Library, 2016).

  60. Lawson, C. L. & Hanson, R. J. Solving Least Squares Problems (Society for Industrial and Applied Mathematics, 1995).

  61. Kass, R. E. & Raftery, A. E. Bayes factors. J. Am. Stat. Assoc. 90, 773–795 (1995).

    Article  MathSciNet  Google Scholar 

  62. Benneke, B. & Seager, S. How to distinguish between cloudy mini-Neptunes and water/volatile-dominated super-Earths. Astrophys. J. 778, 153 (2013).

    Article  ADS  Google Scholar 

  63. de Regt, S. et al. The ESO SupJup Survey – I. Chemical and isotopic characterisation of the late L-dwarf DENIS J0255-4700 with CRIRES+. Astron. Astrophys. 688, A116 (2024).

    Article  Google Scholar 

  64. Polyansky, O. L. et al. ExoMol molecular line lists XIX: high-accuracy computed hot line lists for \({{\rm{H}}}_{2}^{18}\rm{O}\) and \({{\rm{H}}}_{2}^{18}\rm{O}\). Mon. Not. R. Astron. Soc. 466, 1363–1371 (2017).

    Article  ADS  Google Scholar 

  65. González Picos, D., Snellen, I. & de Regt, S. Chemical evolution imprints in rare isotopes of nearby M dwarfs. Zenodo https://doi.org/10.5281/zenodo.15828872 (2025).

  66. Gaia Collaboration et al. Gaia Early Data Release 3: summary of the contents and survey properties. Astron. Astrophys. 649, A1 (2021).

  67. Lyons, J. R., Gharib-Nezhad, E. & Ayres, T. R. A light carbon isotope composition for the Sun. Nat. Commun. 9, 908 (2018).

    Article  ADS  Google Scholar 

  68. Wang, X.-L., Fang, M., Liu, Y., Zhang, M.-M. & Cui, W.-Y. LAMOST reveals long-lived protoplanetary disks. Astron. J. 169, 141 (2025).

    Article  Google Scholar 

  69. Ribas, I. et al. A candidate super-Earth planet orbiting near the snow line of Barnard’s star. Nature 563, 365–368 (2018).

    Article  ADS  Google Scholar 

  70. Bouvier, A. & Wadhwa, M. The age of the Solar System redefined by the oldest Pb–Pb age of a meteoritic inclusion. Nat. Geosci. 3, 637–641 (2010).

    Article  ADS  Google Scholar 

  71. Asplund, M., Amarsi, A. M. & Grevesse, N. The chemical make-up of the Sun: a 2020 vision. Astron. Astrophys. 653, A141 (2021).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

D.G.P. thanks D. Romano for providing the GCE models and valuable insights on the evolution of isotope ratios. D.G.P., I.S. and S.d.R. acknowledge NWO grant OCENW.M.21.010. This work used the Dutch national e-infrastructure with the support of the SURF Cooperative via grant no. EINF-4556. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated from the summit of Maunakea by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France and the University of Hawaii. The observations at the Canada-France-Hawaii Telescope were performed with care and respect from the summit of Maunakea, which is a significant cultural and historic site. This work is based on observations obtained with SPIRou, an international project led by the Institut de Recherche en Astrophysique et Planétologie (IRAP) in Toulouse, France.

Author information

Authors and Affiliations

  1. Leiden Observatory, Leiden University, Leiden, the Netherlands

    Darío González Picos, Ignas Snellen & Sam de Regt

Authors
  1. Darío González Picos
    View author publications

    Search author on:PubMed Google Scholar

  2. Ignas Snellen
    View author publications

    Search author on:PubMed Google Scholar

  3. Sam de Regt
    View author publications

    Search author on:PubMed Google Scholar

Contributions

D.G.P. led the data processing and analysis and wrote the paper. I.S. contributed to the model fitting, interpretation of the results and writing of the paper. S.d.R. contributed to the code development of the models, provided the code for the opacity calculator and advised on model fitting. All authors contributed to the text and figures of the paper.

Corresponding author

Correspondence to Ignas Snellen.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Astronomy thanks Paul Cristofari and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

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

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) 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

González Picos, D., Snellen, I. & de Regt, S. Chemical evolution imprints in the rare isotopes of nearby M dwarfs. Nat Astron (2025). https://doi.org/10.1038/s41550-025-02641-4

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1038/s41550-025-02641-4

Search

Advanced search

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