Newly synthesized lithium in the interstellar medium


Astronomical observations of elemental and isotopic abundances provide the means to determine the source of elements and to reveal their evolutionary pathways since the formation of the Galaxy some 15 billion years ago. The abundance of lithium is particularly interesting because, although some of it is thought to be primordial, most results from spallation reactions (in which Galactic cosmic rays break apart larger nuclei in the interstellar medium). Spallation reactions are crucial for the production of other light elements1, such as beryllium and boron, so observations of lithium isotopic abundances can be used to test model predictions2,3,4,5 for light-element synthesis in general. Here we report observations of 7Li and 6Li abundances in several interstellar clouds lying in the direction of the star ο Persei. We find the abundance ratio 7Li/6Li to be about 2, which is significantly lower than the average Solar System value of 12.3 (refs 6, 7). An abundance ratio of 2 is clear evidence that the observed lithium must have resulted entirely from spallation, confirming a basic tenet of light-element synthesis2,3,4,5. The total lithium abundance, however, is not enhanced as expected.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Interstellar spectra of K I and Li I toward ζ and ο Per.


  1. 1

    Reeves, H., Fowler, W. A. & Hoyle, F. Galactic cosmic ray origin of Li, Be and B in stars. Nature 226, 727–729 (1970).

    ADS  Article  Google Scholar 

  2. 2

    Meneguzzi, M., Audouze, J. & Reeves, H. The production of the elements Li, Be, B by galactic cosmic rays in space and its relation with stellar observations. Astron. Astrophys. 15, 337–359 (1971).

    ADS  CAS  Google Scholar 

  3. 3

    Meneguzzi, M. & Reeves, H. Light element production by cosmic rays. Astron. Astrophys. 40, 99–110 (1975).

    ADS  CAS  Google Scholar 

  4. 4

    Ramaty, R., Kozlovsky, B. & Lingenfelter, R. E. Light isotopes, extinct radioisotopes, and gamma-ray lines from low-energy cosmic-ray interactions. Astrophys. J. 456, 525–540 (1996).

    ADS  CAS  Article  Google Scholar 

  5. 5

    Lemoine, M., Vangioni-Flam, E. & Cassé, M. Galactic cosmic rays and the evolution of light elements. Astrophys. J. 499, 735–745 (1998).

    ADS  CAS  Article  Google Scholar 

  6. 6

    Anders, E. & Grevesse, N. Abundances of the elements: meteoritic and solar. Geochim. Cosmochim. Acta 53, 197–214 (1989).

    ADS  CAS  Article  Google Scholar 

  7. 7

    Chaussidon, M. & Robert, F. 7Li/6Li and 11B/10B variations in chondrules from the Semarkona unequilibrated chondrite. Earth Planet. Sci. Lett. 164, 577–589 (1998).

    ADS  CAS  Article  Google Scholar 

  8. 8

    Tull, R. G., MacQueen, P. J., Sneden, C. & Lambert, D. L. The high resolution cross-dispersed echelle white-pupil spectrometer of the McDonald Observatory 2.7 m telescope. Publ. Astron. Soc. Pacif. 107, 251–264 (1995).

    ADS  Article  Google Scholar 

  9. 9

    Lemoine, M., Ferlet, R., Vidal-Madjar, A., Emerich, C. & Bertin, P. Interstellar lithium and the 7Li/6Li ratio toward ρ Oph. Astron. Astrophys. 269, 469–476 (1993).

    ADS  CAS  Google Scholar 

  10. 10

    Lemoine, M., Ferlet, R. & Vidal-Madjar, A. The interstellar 7Li/6Li ratio. The line of sight to ζ Ophiuchi. Astron. Astrophys. 298, 879–893 (1995).

    ADS  CAS  Google Scholar 

  11. 11

    Morton, D. C. Atomic data for resonance absorption lines. I. Wavelengths longward of the Lyman limit. Astrophys. J. Suppl. 77, 119–202 (1991).

    ADS  CAS  Article  Google Scholar 

  12. 12

    Federman, S. R., Lambert, D. L., Cardelli, J. A. & Sheffer, Y. The boron isotope ratio in the interstellar medium. Nature 381, 764–766 (1995).

    ADS  Article  Google Scholar 

  13. 13

    Lambert, D. L. et al. The 11B/10B ratio of local interstellar diffuse clouds. Astrophys. J. 494, 614–622 (1998).

    ADS  CAS  Article  Google Scholar 

  14. 14

    Meyer, D. M., Hawkins, I. & Wright, E. L. The interstellar 7Li/6Li isotope ratio toward ζ Ophiuchi and ζ Persei. Astrophys. J. 409, L61–L64 (1993).

    ADS  CAS  Article  Google Scholar 

  15. 15

    van Dishoeck, E. F. & Black, J. H. Comprehensive models of diffuse interstellar clouds: Physical conditions and molecular abundances. Astrophys. J. Suppl. 62, 109–145 (1986).

    ADS  CAS  Article  Google Scholar 

  16. 16

    Federman, S. R., Weber, J. & Lambert, D. L. Cosmic ray-induced chemistry toward Perseus OB2. Astrophys. J. 463, 181–190 (1996).

    ADS  CAS  Article  Google Scholar 

  17. 17

    Crane, P., Lambert, D. L. & Sheffer, Y. A very high resolution survey of interstellar CH and CH+. Astrophys. J. Suppl. 99, 107–120 (1995).

    ADS  CAS  Article  Google Scholar 

  18. 18

    White, R. E. Interstellar lithium: differential depletion in diffuse clouds. Astrophys. J. 307, 777–786 (1986).

    ADS  CAS  Article  Google Scholar 

  19. 19

    Andersen, J., Gustafsson, B. & Lambert, D. L. The lithium isotope ratio in F and G stars. Astron. Astrophys. 136, 65–73 (1984).

    ADS  CAS  Google Scholar 

  20. 20

    Parizot, E. & Drury, L. Superbubbles as the source of 6Li, Be, and B in the early Galaxy. Astron. Astrophys. 349, 673–684 (1999).

    ADS  CAS  Google Scholar 

  21. 21

    Snow, T. P. Jr lnterstellar molecular abundances toward omicron Persei. Astrophys. J. 201, L21–L24 (1975).

    ADS  CAS  Article  Google Scholar 

  22. 22

    Sansonetti, C. J., Richou, B., Engleman, R. Jr & Radziemski, L. J. Measurements of the resonance lines of 6Li and 7Li by Doppler-free frequency-modulation spectroscopy. Phys. Rev. A 52, 2682–2688 (1995).

    ADS  CAS  Article  Google Scholar 

  23. 23

    Hobbs, L. M., Thorburn, J. A. & Rebull, L. M. Lithium isotope ratios in halo stars. III. Astrophys. J. 523, 797–804 (1999).

    ADS  CAS  Article  Google Scholar 

  24. 24

    Sofia, U. J., Cardelli, J. A., Guerin, K. P. & Meyer, D. M. Carbon in the diffuse interstellar medium. Astrophys. J. 482, L105–L108 (1997).

    ADS  CAS  Article  Google Scholar 

  25. 25

    Cardelli, J. A., Meyer, D. M., Jura, M. & Savage, B. D. The abundance of interstellar carbon. Astrophys. J. 467, 334–340 (1996).

    ADS  CAS  Article  Google Scholar 

  26. 26

    Savage, B. D., Bohlin, R. C., Drake, J. F. & Budich, W. A survey of interstellar molecular hydrogen. Astrophys. J. 216, 291–307 (1977).

    ADS  CAS  Article  Google Scholar 

  27. 27

    Diplas, A. & Savage, B. D. An IUE survey of interstellar H I Lyα absorption. I. Column densities. Astrophys. J. Suppl. 93, 211–228 (1994).

    ADS  CAS  Article  Google Scholar 

  28. 28

    Federman, S. R. et al. Chemical transitions for interstellar C2 and CN in cloud envelopes. Astrophys. J. 424, 772–792 (1994).

    ADS  CAS  Article  Google Scholar 

Download references


We thank E. Parizot and H. Reeves for fruitful discussions. This work was supported by the National Aeronautics and Space Administration. We made use of the Simbad database, operated at Centre de Donées Astronomiques de Strasbourg, Strasbourg, France.

Author information



Corresponding author

Correspondence to S. R. Federman.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Knauth, D., Federman, S., Lambert, D. et al. Newly synthesized lithium in the interstellar medium. Nature 405, 656–658 (2000).

Download citation

Further reading


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.


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