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.

A close halo of large transparent grains around extreme red giant stars

Subjects

Abstract

An intermediate-mass star ends its life by ejecting the bulk of its envelope in a slow, dense wind1,2,3. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust1, which is then accelerated by radiation pressure, entraining the gas and driving the wind2,4,5. Explaining the amount of mass loss, however, has been a problem because of the difficulty of observing tenuous gas and dust only tens of milliarcseconds from the star. For this reason, there is no consensus on the way sufficient momentum is transferred from the light from the star to the outflow. Here we report spatially resolved, multiwavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the Hertzsprung–Russell diagram. When imaged in scattered light, dust shells were found at remarkably small radii (less than about two stellar radii) and with unexpectedly large grains (about 300 nanometres in radius). This proximity to the photosphere argues for dust species that are transparent to the light from the star and, therefore, resistant to sublimation by the intense radiation field. Although transparency usually implies insufficient radiative pressure to drive a wind6,7, the radiation field can accelerate these large grains through photon scattering rather than absorption8—a plausible mass loss mechanism for lower-amplitude pulsating stars.

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

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Polarimetric interferometry of W Hya at 1.24 μm.
Figure 2: Wavelength dependence of scattering for W Hya and R Dor.
Figure 3: Model image for W Hya with circumstellar shell viewed in horizontally and vertically polarized light.
Figure 4: Grain size measurement.

References

  1. Wood, P. R. Pulsation and mass loss in Mira variables. Astrophys. J. 227, 220–231 (1979)

    Article  ADS  CAS  Google Scholar 

  2. Habing, H. J. Circumstellar envelopes and asymptotic giant branch stars. Astron. Astrophys. Rev. 7, 97–207 (1996)

    Article  ADS  Google Scholar 

  3. Marengo, M. A review of AGB mass loss imaging techniques. Proc. Astron. Soc. Aust. 26, 365–371 (2009)

    Article  ADS  Google Scholar 

  4. Gustafsson, B. & Höfner, S. Asymptotic Giant Branch Stars (eds Habing, H. J. & Olofsson, H. ) Ch. 4 (Springer, 2004)

    Google Scholar 

  5. Höfner, S. Dust formation and winds around evolved stars: the good, the bad and the ugly cases. Astron. Soc. Pacif. Conf. Ser. 414, 3–21 (2009)

    ADS  Google Scholar 

  6. Woitke, P. Too little radiation pressure on dust in the winds of oxygen-rich AGB stars. Astron. Astrophys. 460, L9–L12 (2006)

    Article  ADS  CAS  Google Scholar 

  7. Ireland, M. J. & Scholz, M. Observable effects of dust formation in dynamic atmospheres of M-type Mira variables. Mon. Not. R. Astron. Soc. 367, 1585–1593 (2006)

    Article  ADS  CAS  Google Scholar 

  8. Höfner, S. Winds of M-type AGB stars driven by micron-sized grains. Astron. Astrophys. 491, L1–L4 (2008)

    Article  ADS  Google Scholar 

  9. Tuthill, P. G., Monnier, J. D., Danchi, W. C., Wishnow, E. H. & Haniff, C. A. Michelson interferometry with the Keck I Telescope. Publ. Astron. Soc. Pacif. 112, 555–565 (2000)

    Article  ADS  Google Scholar 

  10. Lacour, S. et al. Sparse aperture masking at the VLT. I. Faint companion detection limits for the two debris disk stars HD 92945 and HD 141569. Astron. Astrophys. 532, A72 (2011)

    Article  Google Scholar 

  11. Wittkowski, M. et al. The extended atmospheres of Mira variables probed by VLTI, VLBA, and APEX. Astron. Soc. Pacif. Conf. Ser. 445, 107–112 (2011)

    ADS  CAS  Google Scholar 

  12. Ireland, M. J., Tuthill, P. G., Davis, J. & Tango, W. Dust scattering in the Miras R Car and RR Sco resolved by optical interferometric polarimetry. Mon. Not. R. Astron. Soc. 361, 337–344 (2005)

    Article  ADS  Google Scholar 

  13. Waters, L. B. F. M. et al. Mineralogy of oxygen-rich dust shells. Astron. Astrophys. 315, L361–L364 (1996)

    ADS  CAS  Google Scholar 

  14. Gail, H.-P. in Astromineralogy (ed Henning, T. K. ) 55–120 (Lect. Notes Phys. 609, Springer, 2003)

    Book  Google Scholar 

  15. Draine, B. T. Interstellar dust grains. Annu. Rev. Astron. Astrophys. 41, 241–289 (2003)

    Article  ADS  Google Scholar 

  16. Frisch, P. C. et al. Dust in the local interstellar wind. Astrophys. J. 525, 492–516 (1999)

    Article  ADS  CAS  Google Scholar 

  17. Weingartner, J. C. & Draine, B. T. Dust grain-size distributions and extinction in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud. Astrophys. J. 548, 296–309 (2001)

    Article  ADS  Google Scholar 

  18. Lagadec, E. & Zijlstra, A. A. The trigger of the asymptotic giant branch superwind: the importance of carbon. Mon. Not. R. Astron. Soc. 390, L59–L63 (2008)

    Article  ADS  Google Scholar 

  19. Ireland, M. J., Scholz, M. & Wood, P. R. Dynamical opacity-sampling models of Mira variables - II. Time-dependent atmospheric structure and observable properties of four M-type model series. Mon. Not. R. Astron. Soc. 418, 114–128 (2011)

    Article  ADS  Google Scholar 

  20. Loup, C., Forveille, T., Omont, A. & Paul, J. F. CO and HCN observations of circumstellar envelopes. A catalogue—mass loss rates and distributions. Astron. Astrophys. Suppl. Ser. 99, 291–377 (1993)

    ADS  CAS  Google Scholar 

  21. Olofsson, H., González Delgado, D., Kerschbaum, F. & Schöier, F. L. Mass loss rates of a sample of irregular and semiregular M-type AGB-variables. Astron. Astrophys. 391, 1053–1067 (2002)

    Article  ADS  Google Scholar 

  22. van Leeuwen, F. Validation of the new Hipparcos reduction. Astron. Astrophys. 474, 653–664 (2007)

    Article  ADS  Google Scholar 

  23. Jäger, C., Dorschner, J., Mutschke, H., Posch, T. & Henning, T. Steps toward interstellar silicate mineralogy. VII. Spectral properties and crystallization behaviour of magnesium silicates produced by the sol-gel method. Astron. Astrophys. 408, 193–204 (2003)

    Article  ADS  Google Scholar 

  24. Lenzen, R. et al. NAOS-CONICA first on sky results in a variety of observing modes. Proc. SPIE 4841, 944–952 (2003)

    Article  ADS  Google Scholar 

  25. Tuthill, P. et al. Sparse aperture masking (SAM) at NAOS/CONICA on the VLT. Proc. SPIE 7735, 77351O (2010)

    Article  Google Scholar 

Download references

Acknowledgements

This work was based on observations collected with the NACO instrument at the European Southern Observatory, Chile.

Author information

Authors and Affiliations

Authors

Contributions

P.G.T., M.J.I. and S.L. commissioned the SAMPol observing mode and conducted the initial observations, and developed the standard aperture-masking data reduction pipeline. B.R.M.N. developed the polarimetric data reduction and modelling/fitting procedures, analysed the data and conducted later observations. T.M.E. and P.S. contributed to the data analysis procedures. T.R.B., A.A.Z. and F.L. contributed to both the observing programme and the interpretation of the findings.

Corresponding author

Correspondence to Barnaby R. M. Norris.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Text, Supplementary Figures 1-2 and additional references. The Supplementary Text contains a detailed description of the modelling process used in these investigations and additional discussion regarding other dust species. This section also refers to Supplementary Figure 1, a diagram explaining the geometry of the model used. Supplementary Figure 2 shows a diagram demonstrating how starlight becomes polarised by a spherical scattering shell. (PDF 767 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Norris, B., Tuthill, P., Ireland, M. et al. A close halo of large transparent grains around extreme red giant stars. Nature 484, 220–222 (2012). https://doi.org/10.1038/nature10935

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature10935

This article is cited by

Comments

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.

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