Skip to main content

Thank you for visiting 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.

Radiative acceleration of gas in quasars


QUASARS can radiate up to a thousand times the energy of the entire Galaxy, yet this energy is generated in a small region approximately one light day across. (By comparison, the diameter of the Milky Way is about 100,000 light years.) Because of the high energy density in this region, it has often been suggested that radiation pressure might play an important dynamical role in quasars1á¤-3. Here we show that radiative acceleration can readily explain a prominent feature observed in the spectra of several broad-absorption-line (BAL) quasars. The broad absorption lines are themselves attributed to matter flowing towards the observer with velocities approaching one-tenth of the speed of light4,5, and our results suggest that radiative acceleration is the dominant driving mechanism in these outflows. As most quasars are believed to have BAL outflows6 (although they are seen in only about 10% of them because of viewing angle7,8), radiative acceleration is likely to be an important dynamical process in quasars in general.

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

Access options

Rent or buy this article

Prices vary by article type



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


  1. Scargle, J. D., Caroff, L. J. & Noerdlinger, P. D. Astrophys. J. 161, L115–L121 (1970).

    Article  ADS  Google Scholar 

  2. McKee, C. F. & Tarter, C. B. Astrophys. J. 202, 306–318 (1975).

    Article  ADS  CAS  Google Scholar 

  3. Drew, J. E. & Boksenberg, A. Mon. Not. R. astr. Soc. 211, 813–831 (1984).

    Article  ADS  CAS  Google Scholar 

  4. Weymann, R. J., Turnshek, D. A. & Christiansen, W. A. in Astrophysics of Active Galaxies and Quasi-stellar Objects (ed. Miller, J.) 333–365 (Oxford Univ. Press, 1985).

    Google Scholar 

  5. Turnshek, D. A. in Proc. 2nd Symp. Space Telescope Science Inst. (eds Blades, S. C, Turnshek, D. A. & Norman, C. A.) 17–51 (Cambridge Univ. Press, 1988).

    Google Scholar 

  6. Weymann, R. J., Morris, S. L., Foltz, C. B. & Hewett, P. C. Astrophys. J. 373, 23–53 (1991).

    Article  ADS  CAS  Google Scholar 

  7. Foltz, C. B., Chafee, F. H., Hewett, P. C., Weymann, R. J. & Morris, S. L. Bull. Am. astr. Soc. 2, 806 (1990).

    ADS  Google Scholar 

  8. Hamann, F., Korista, T. K. & Morris, S. L. Astrophys. J. 415, 541–562 (1993).

    Article  ADS  CAS  Google Scholar 

  9. Turnshek, D. A., Foltz, C. B., Grillmair, C. J. & Weymann, R. J. Astrophys. J. 325, 651–670 (1988).

    Article  ADS  CAS  Google Scholar 

  10. Korista, T. K., Voit, G. M., Morris, S. L. & Weymann, R. J. Astrophys. J. Suppl. Ser. 88, 357–381 (1993).

    Article  ADS  CAS  Google Scholar 

  11. Arav, N. & Begelman, M. C. Astrophys. J. 434, 479–483 (1994).

    Article  ADS  CAS  Google Scholar 

  12. Netzer, H. in Active Galactic Nuclei (eds Blandford, R. D., Netzer, H. & Woltjer, L.) 57–160 (Springer, New York, 1990).

    Google Scholar 

  13. Arav, N., Li, Z. Y. & Begelman, M. C. Astrophys. J. 432, 62–74 (1994).

    Article  ADS  CAS  Google Scholar 

  14. Mathews, W. G. & Ferland, G. J. Astrophys. J. 323, 456–467 (1987).

    Article  ADS  CAS  Google Scholar 

  15. Michalitsianos, A. G. & Oliversen, R. J. Astrophys. J. 439, 599–603 (1995).

    Article  ADS  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Arav, N., Korista, K., Barlow, T. et al. Radiative acceleration of gas in quasars. Nature 376, 576–578 (1995).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


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.


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