Abstract

Nearly a century ago it was recognized1 that radiation absorption by stellar matter controls the internal temperature profiles within stars. Laboratory opacity measurements, however, have never been performed at stellar interior conditions, introducing uncertainties in stellar models2,3,4,5. A particular problem arose2,3,6,7,8 when refined photosphere spectral analysis9,10 led to reductions of 30–50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the Sun. Standard solar models11 using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. This could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted2,3,6,7,8, because increased opacity compensates for the decreased element abundances. Iron accounts for a quarter of the total opacity2,12 at the solar radiation/convection zone boundary. Here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9–2.3 million kelvin and electron densities of (0.7–4.0) × 1022 per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. The measured wavelength-dependent opacity is 30–400 per cent higher than predicted. This represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity.

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References

  1. 1.

    The Internal Constitution of the Stars (Cambridge Univ. Press, 1926)

  2. 2.

    & Helioseismology and solar abundances. Phys. Rep. 457, 217–283 (2008)

  3. 3.

    , , & Understanding the internal chemical composition and physical processes of the solar interior. Space Sci. Rev. (2014)

  4. 4.

    in Proc. IAU Symp. No. 258, The Ages of Stars (2008) (eds , & ) 431–442 (International Astronomical Union, 2009)

  5. 5.

    & Comparison of radiative accelerations obtained with atomic data from OP and OPAL. Astrophys. J. 625, 563–574 (2005)

  6. 6.

    , & How accurately can we calculate the depth of the solar convective zone? Astrophys. J. 614, 464–471 (2004)

  7. 7.

    et al. Surprising Sun: a new step towards a complete picture? Phys. Rev. Lett. 93, 211102 (2004)

  8. 8.

    , , & New solar composition: the problem with solar models revisited. Astrophys. J. 705, L123–L127 (2009)

  9. 9.

    , , & The chemical composition of the Sun. Annu. Rev. Astron. Astrophys. 47, 481–522 (2009)

  10. 10.

    et al. Solar chemical abundances determined with a CO5BOLD 3D model atmosphere. Sol. Phys. 268, 255–269 (2011)

  11. 11.

    et al. Standard solar models and the uncertainties in predicted capture rates of solar neutrinos. Rev. Mod. Phys. 54, 767–799 (1982)

  12. 12.

    , & Solar mixture opacity calculations using detailed configuration and level accounting treatments. Astrophys. J. 745, 10 (2012)

  13. 13.

    , , & Highly excited core resonances in photoionization of Fe XVII: implications for plasma opacities. Phys. Rev. A 83, 053417 (2011)

  14. 14.

    Note on the absorption of radiation within a star. Mon. Not. R. Astron. Soc. 84, 525–528 (1924)

  15. 15.

    et al. Absorption experiments on x-ray-heated mid-Z constrained samples. Phys. Rev. E 54, 5617–5631 (1996)

  16. 16.

    et al. Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas. Phys. Plasmas 16, 058101 (2009)

  17. 17.

    et al. Iron-plasma transmission measurements at temperatures above 150 eV. Phys. Rev. Lett. 99, 265002 (2007)

  18. 18.

    et al. ZAPP: the Z Astrophysical Plasma Properties collaboration. Phys. Plasmas 21, 056308 (2014)

  19. 19.

    et al. Investigation of the opacity of hot, dense aluminum in the region of its K edge. Appl. Phys. Lett. 52, 847–849 (1988)

  20. 20.

    et al. L-shell absorption spectrum of an open-M-shell germanium plasma: comparison of experimental data with a detailed configuration-accounting calculation. Phys. Rev. Lett. 67, 3255–3258 (1991)

  21. 21.

    , & Design of dynamic Hohlraum opacity samples to increase measured sample density on Z. Rev. Sci. Instrum. 81, 10E518 (2010)

  22. 22.

    et al. Control and diagnosis of temperature, density, and uniformity in x-ray heated iron/magnesium samples for opacity measurements. Phys. Plasmas 21, 056502 (2014)

  23. 23.

    , , & Hybrid atomic models for spectroscopic plasma diagnostics. High Energy Density Phys. 3, 109–114 (2007)

  24. 24.

    & Opacities for the solar radiative interior. Astrophys. J. 371, 408–417 (1991)

  25. 25.

    , , & Opacities for stellar envelopes. Mon. Not. R. Astron. Soc. 266, 805–828 (1994)

  26. 26.

    et al. Updated opacities from the opacity project. Mon. Not. R. Astron. Soc. 360, 458–464 (2005)

  27. 27.

    et al. Light element opacities from ATOMIC. High Energy Density Phys. 9, 369–374 (2013)

  28. 28.

    , , & A consistent approach for mixed detailed and statistical calculation of opacities in hot plasmas. High Energy Density Phys. 7, 234–239 (2011)

  29. 29.

    et al. Dynamic hohlraum radiation hydrodynamics. Phys. Plasmas 13, 056301 (2006)

  30. 30.

    et al. Diagnosis of x-ray heated Mg/Fe opacity research plasmas. Rev. Sci. Instrum. 79, 113104 (2008)

  31. 31.

    , & Accurate determination of quantity of material in thin films by Rutherford backscattering spectrometery. Anal. Chem. 84, 6061–6069 (2012)

  32. 32.

    et al. A methodology for calibrating wavelength dependent spectral resolution for crystal spectrometers. Rev. Sci. Instrum. 83, 10E133 (2012)

  33. 33.

    et al. Low-energy x-ray response of photographic films. II. Experimental characterization. J. Opt. Soc. Am. B 1, 828–849 (1984)

  34. 34.

    et al. Parallax diagnostics of radiation source geometric dilution for iron opacity experiments. Rev. Sci. Instrum. 85, 11D603 (2014)

  35. 35.

    et al. in Proc. Int. Symp. on Inertial Fusion Science and Applications (Monterey, California, 2003) 457–464 (American Nuclear Society, 2003)

  36. 36.

    , & X-ray interactions: photoabsorption, scattering, transmission, and reflection at E = 50-30,000 eV, Z = 1-92. At. Data Nucl. Data Tables 54, 181–342 (1993)

  37. 37.

    L Shell photoabsorption spectroscopy for solid metals: Ti, V, Cr, Fe, Ni, Cu. Phys. Scr. 41, 110–114 (1990)

  38. 38.

    , , & Determination of the photoabsorption cross-sections of Al and Fe films in the soft x-ray region using synchrotron radiation. High Energy Phys. Nuclear Phys. 28, 1121–1125 (2004)

  39. 39.

    The Theory of Atomic Structure and Spectra (Univ. California Press, 1981)

  40. 40.

    , & HELIOS-CR—a 1-D radiation-magnetohydrodynamics code with inline atomic kinetics modeling. J. Quant. Spectrosc. Radiat. Transf. 99, 381–397 (2006)

  41. 41.

    et al. Investigation of iron opacity experiment plasma gradients with synthetic data analyses. Rev. Sci. Instrum. 83, 10E128 (2012)

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Acknowledgements

Sandia is a multiprogramme laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000. The Los Alamos National Laboratory is operated by Los Alamos National Security, LLC, for the NNSA of the US DOE under contract number DE-AC5206NA25396. J.E.B. acknowledges support from a DOE High Energy Density Laboratory Plasmas grant. A.K.P. and C.O. also acknowledge support from a DOE High Energy Density Laboratory Plasmas grant. We appreciate the efforts of the entire Z facility team. We thank S. Turck-Chièze, H. Morris, and M. Pinsonneault for discussions. We also thank R. W. Lee for critiquing the manuscript. We appreciate support for the experiments provided by R. J. Leeper, J. L. Porter, M. K. Matzen and M. Herrmann.

Author information

Affiliations

  1. Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87185-1196, USA

    • J. E. Bailey
    • , T. Nagayama
    • , G. P. Loisel
    • , G. A. Rochau
    •  & S. B. Hansen
  2. Commissariat à l’Énergie Atomique (CEA) et aux Énergies Alternatives, F-91297 Arpajon, France

    • C. Blancard
    • , Ph. Cosse
    • , G. Faussurier
    • , F. Gilleron
    •  & J.-C. Pain
  3. Los Alamos National Laboratory, Bikini Atoll Road, Los Alamos, New Mexico 87545, USA

    • J. Colgan
    • , C. J. Fontes
    • , D. P. Kilcrease
    •  & M. Sherrill
  4. Prism Computational Sciences, 455 Science Drive, Suite 140, Madison, Wisconsin 53711, USA

    • I. Golovkin
    •  & J. J. MacFarlane
  5. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550-9234, USA

    • C. A. Iglesias
    •  & B. G. Wilson
  6. University of Nevada, 1664 North Virginia Street, Reno, Nevada 89557, USA

    • R. C. Mancini
  7. Ohio State University, 140 West 18th Avenue, Columbus, Ohio 43210, USA

    • S. N. Nahar
    • , C. Orban
    •  & A. K. Pradhan

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Contributions

These measurements were conceived and planned by J.E.B. and G.A.R. J.E.B. was the primary author of the manuscript, with important contributions from T.N. Experiments were conducted by J.E.B., G.A.R. and G.P.L. The Z-facility data were analysed by T.N., J.E.B. and G.P.L., with assistance from G.A.R., C.A.I., B.G.W., I.G., J.J. M. and R.C.M. OPAS calculations were performed by C.B., G.F. and Ph.C. ATOMIC calculations were performed by J.C., with assistance from C.F., D.P.K. and M.S. SCRAM calculations were provided by S.B.H. SCO calculations were performed by J.-C.P. and F.G. OP calculations were performed by C.O., with assistance from A.K.P. and S.N.N. All authors discussed the results, commented on the manuscript, and contributed to the interpretation.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to J. E. Bailey.

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https://doi.org/10.1038/nature14048

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