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Observation of interstellar lithium in the low-metallicity Small Magellanic Cloud


The primordial abundances of light elements produced in the standard theory of Big Bang nucleosynthesis (BBN) depend only on the cosmic ratio of baryons to photons, a quantity inferred from observations of the microwave background1. The predicted2,3,4 primordial 7Li abundance is four times that measured in the atmospheres of Galactic halo stars5,6,7. This discrepancy could be caused by modification of surface lithium abundances during the stars’ lifetimes8 or by physics beyond the Standard Model that affects early nucleosynthesis9,10. The lithium abundance of low-metallicity gas provides an alternative constraint on the primordial abundance and cosmic evolution of lithium11 that is not susceptible to the in situ modifications that may affect stellar atmospheres. Here we report observations of interstellar 7Li in the low-metallicity gas of the Small Magellanic Cloud, a nearby galaxy with a quarter the Sun’s metallicity. The present-day 7Li abundance of the Small Magellanic Cloud is nearly equal to the BBN predictions, severely constraining the amount of possible subsequent enrichment of the gas by stellar and cosmic-ray nucleosynthesis. Our measurements can be reconciled with standard BBN with an extremely fine-tuned depletion of stellar Li with metallicity. They are also consistent with non-standard BBN.

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Figure 1: Interstellar absorption by several neutral species seen towards the star Sk 143.
Figure 2: Estimates of the lithium abundance in the SMC interstellar medium and in other environments.
Figure 3: Estimates of Li/Fe in the SMC interstellar medium and in several different environments.


  1. 1

    Dunkley, J. et al. Five-year Wilkinson Microwave Anisotropy Probe observations: likelihoods and parameters from the WMAP data. Astrophys. J. 180 (Suppl.). 306–329 (2009)

    CAS  Article  Google Scholar 

  2. 2

    Steigman, G. Primordial nucleosynthesis in the precision cosmology era. Ann. Rev. Nuclear Particle Sci. 57, 463–491 (2007)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Cyburt, R. H., Fields, B. D. & Olive, K. A. An update on the big bang nucleosynthesis prediction for 7Li: the problem worsens. J. Cosmol. Astro-Particle Phys. 11, 012 (2008)

    ADS  Article  Google Scholar 

  4. 4

    Fields, B. D. The primordial lithium problem. Ann. Rev. Nuclear Particle Sci. 61, 47–68 (2011)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Spite, M. & Spite, F. Lithium abundance at the formation of the Galaxy. Nature 297, 483–485 (1982)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Sbordone, L. et al. The metal-poor end of the Spite plateau. 1: Stellar parameters, metallicities and lithium abundances. Astron. Astrophys. 522, A26 (2010)

    Article  Google Scholar 

  7. 7

    Meléndez, J., Casagrande, L., Ramírez, I., Asplund, M. & Schuster, W. J. Observational evidence for a broken Li Spite plateau and mass-dependent Li depletion. Astron. Astrophys. 515, L3–L7 (2010)

    ADS  Article  Google Scholar 

  8. 8

    Korn, A. J. et al. A probable stellar solution to the cosmological lithium discrepancy. Nature 442, 657–659 (2006)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Jedamzik, K. Did something decay, evaporate, or annihilate during big bang nucleosynthesis? Phys. Rev. D 70, 063524 (2004)

    ADS  Article  Google Scholar 

  10. 10

    Pospelov, M. & Pradler, J. Big Bang nucleosynthesis as a probe of new physics. Ann. Rev. Nuclear Particle Sci. 60, 539–568 (2010)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Prodanović, T. & Fields, B. D. Probing primordial and pre-galactic lithium with high-velocity clouds. Astrophys. J. 616, L115–L118 (2004)

    ADS  Article  Google Scholar 

  12. 12

    Dekker, H., D'Odorico, S., Kaufer, A., Delabre, B. & Kotzlowski, H. Design, construction, and performance of UVES, the echelle spectrograph for the UT2 Kueyen Telescope at the ESO Paranal Observatory. Proc. SPIE 4008, 534–545 (2000)

    ADS  Article  Google Scholar 

  13. 13

    Cox, N. L. J. et al. Interstellar gas, dust and diffuse bands in the SMC. Astron. Astrophys. 470, 941–955 (2007)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Welty, D. E., Federman, S. R., Gredel, R., Thorburn, J. A. & Lambert, D. L. VLT UVES observations of interstellar molecules and diffuse bands in the Magellanic clouds. Astrophys. J. 165 (Suppl.). 138–172 (2006)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Cartledge, S. I. B. et al. FUSE measurements of far-ultraviolet extinction. II. Magellanic cloud sight lines. Astrophys. J. 630, 355–367 (2005)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Steigman, G. Cosmic lithium: going up or coming down? Astrophys. J. 457, 737–742 (1996)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Welty, D. E., Hobbs, L. M. & Morton, D. C. High-resolution observations of interstellar Ca I absorption-implications for depletions and electron densities in diffuse clouds. Astrophys. J. 147 (Suppl.). 61–96 (2003)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Weingartner, J. C. & Draine, B. T. Electron-ion recombination on grains and polycyclic aromatic hydrocarbons. Astrophys. J. 563, 842–852 (2001)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Knauth, D. C., Federman, S. R. & Lambert, D. L. An ultra-high-resolution survey of the interstellar 6Li/7Li isotope ratio in the solar neighborhood. Astrophys. J. 586, 268–285 (2003)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Welty, D. E. & Hobbs, L. M. A. High-resolution survey of interstellar K I absorption. Astrophys. J. 133 (Suppl.). 345–393 (2001)

    ADS  Article  Google Scholar 

  21. 21

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

    ADS  CAS  Article  Google Scholar 

  22. 22

    Lambert, D. L. & Reddy, B. E. Lithium abundances of the local thin disc stars. Mon. Not. R. Astron. Soc. 349, 757–767 (2004)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Prantzos, N. Production and evolution of Li, Be and B isotopes in the Galaxy. Astron. Astrophys. 542, A67 (2012)

    ADS  Article  Google Scholar 

  24. 24

    Romano, D., Tosi, M., Matteucci, F. & Chiappini, C. Light element evolution resulting from WMAP data. Mon. Not. R. Astron. Soc. 346, 295–303 (2003)

    ADS  CAS  Article  Google Scholar 

  25. 25

    Iocco, F., Mangano, G., Miele, G., Pisanti, O. & Serpico, P. D. Primordial nucleosynthesis: from precision cosmology to fundamental physics. Phys. Rep. 472, 1–76 (2009)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Suzuki, T. K. & Inoue, S. Cosmic-ray production of 6Li by structure formation shocks in the early Milky Way: a fossil record of dissipative processes during galaxy formation. Astrophys. J. 573, 168–173 (2002)

    ADS  CAS  Article  Google Scholar 

  27. 27

    Kawanomoto, S. et al. The new detections of 7Li/6Li isotopic ratio in the interstellar media. Astrophys. J. 701, 1506–1518 (2009)

    ADS  CAS  Article  Google Scholar 

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We thank the European Southern Observatory for granting us time for this project as part of proposal 382.B-0556. We also thank A. Fox and H. Sana for discussions about the UVES data and A. Korn, P. Molaro, T. Prodanovic, D. Romano, and D. Welty for input on the project that improved the paper.

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All authors participated in the interpretation and commented on the manuscript. J.C.H. led the project and was responsible for the text of the paper.

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Correspondence to J. Christopher Howk.

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The authors declare no competing financial interests.

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Howk, J., Lehner, N., Fields, B. et al. Observation of interstellar lithium in the low-metallicity Small Magellanic Cloud. Nature 489, 121–123 (2012).

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