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.

Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre


The nuclei of most galaxies are now believed to harbour supermassive black holes1. The motions of stars in the central few light years of our Milky Way Galaxy indicate the presence of a dark object with a mass of about 2.6 × 106 solar masses (refs 2, 3). This object is spatially coincident with the compact radio source Sagittarius A* (Sgr A*) at the dynamical centre of the Galaxy, and the radio emission is thought to be powered by the gravitational potential energy released by matter as it accretes onto a supermassive black hole4,5. Sgr A* is, however, much fainter than expected at all wavelengths, especially in X-rays, which has cast some doubt on this model. The first strong evidence for X-ray emission was found only recently6. Here we report the discovery of rapid X-ray flaring from the direction of Sgr A*, which, together with the previously reported steady X-ray emission, provides compelling evidence that the emission is coming from the accretion of gas onto a supermassive black hole at the Galactic Centre.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Surface plots of the 2–8 keV counts within a 20″ × 20″ field centred on Sgr A* at two epochs.
Figure 2: Light curves of the photon arrival times and band ratios from the direction of Sgr A* on 26–27 October 2000.
Figure 3: X-ray spectra of the Chandra source at the position of Sgr A*.


  1. Richstone, D. et al. Supermassive black holes and the evolution of galaxies. Nature 395 (suppl. on optical astronomy) A14–A19 (1998).

    CAS  Google Scholar 

  2. Genzel, R., Pichon, C., Eckart, A., Gerhard, O. E. & Ott, T. Stellar dynamics in the Galactic Centre: proper motions and anisotropy. Mon. Not. R. Astron. Soc. 317, 348–374 (2000).

    ADS  Article  Google Scholar 

  3. Ghez, A. M., Morris, M., Becklin, E. E., Tanner, A. & Kremenek, T. The accelerations of stars orbiting the Milky Way's central black hole. Nature 407, 349–351 (2000).

    ADS  CAS  Article  PubMed  Google Scholar 

  4. Lynden-Bell, D. & Rees, M. J. On quasars, dust and the Galactic Centre. Mon. Not. R. Astron. Soc. 152, 461–475 (1971).

    ADS  Article  Google Scholar 

  5. Melia, F. & Falcke, H. The supermassive black hole at the Galactic Center. Annu. Rev. Astron. Astrophys. 39, 309–352 (2001).

    ADS  CAS  Article  Google Scholar 

  6. Baganoff, F. K. et al. Chandra X-ray spectroscopic imaging of Sgr A* and the central parsec of the Galaxy. Astrophys. J. (submitted); also preprint astro-ph/0102151 at 〈〉 (2001).

  7. Morris, M. & Serabyn, E. The galactic center environment. Annu. Rev. Astron. Astrophys. 34, 645–702 (1996).

    ADS  CAS  Article  Google Scholar 

  8. Menten, K. M., Reid, M. J., Eckart, A. & Genzel, R. The position of Sagittarius A*: accurate alignment of the radio and infrared reference frames at the Galactic Center. Astrophys. J. 475, L111–L114 (1997).

    ADS  CAS  Article  Google Scholar 

  9. Weisskopf, M. C., O'Dell, S. L. & van Speybroeck, L. P. Advanced X-Ray Astrophysics Facility (AXAF). Proc. SPIE 2805, 2–7 (1996).

    ADS  CAS  Article  Google Scholar 

  10. Predehl, P. & Schmitt, J. H. M. M. X-raying the interstellar medium: ROSAT observations of dust scattering halos. Astron. Astrophys. 293, 889–905 (1995).

    ADS  Google Scholar 

  11. Mushotzky, R. F., Done, C. & Pounds, K. A. X-ray spectra and time variability of active galactic nuclei. Annu. Rev. Astron. Astrophys. 31, 717–761 (1993).

    ADS  CAS  Article  Google Scholar 

  12. Davies, M. B., Blackwell, R., Bailey, V. C. & Sigurdsson, S. The destructive effects of binary encounters on red giants in the Galactic Centre. Mon. Not. R. Astron. Soc. 301, 745–753 (1998).

    ADS  Article  Google Scholar 

  13. Nandra, K., George, I. M., Mushotzky, R. F., Turner, T. J. & Yaqoob, T. ASCA observations of Seyfert 1 galaxies. I. Data analysis, imaging, and timing. Astrophys. J. 476, 70–82 (1997).

    ADS  Article  Google Scholar 

  14. Ptak, A., Yaqoob, T., Mushotzky, R., Serlemitsos, P. & Griffiths, R. X-ray variability as a probe of advection-dominated accretion in low-luminosity active galactic nuclei. Astrophys. J. 501, L37–L40 (1998).

    ADS  Article  Google Scholar 

  15. Ulrich, M.-H., Maraschi, L. & Urry, C. M. Variability of active galactic nuclei. Annu. Rev. Astron. Astrophys. 35, 445–502 (1997).

    ADS  CAS  Article  Google Scholar 

  16. Narayan, R., Mahadevan, R., Grindlay, J. E., Popham, R. G. & Gammie, C. Advection-dominated accretion model of Sagittarius A*: evidence for a black hole at the Galactic center. Astrophys. J. 492, 554–568 (1998).

    ADS  Article  Google Scholar 

  17. Quataert, E. & Narayan, R. Spectral models of advection-dominated accretion flows with winds. Astrophys. J. 520, 298–315 (1999).

    ADS  Article  Google Scholar 

  18. Ball, G. H., Narayan, R. & Quataert, E. Spectral models of convection-dominated accretion flows. Astrophys. J. 552, 221–226 (2001).

    ADS  Article  Google Scholar 

  19. Blandford, R. D. & Begelman, M. C. On the fate of gas accreting at a low rate on to a black hole. Mon. Not. R. Astron. Soc. 303, L1–L5 (1999).

    ADS  Article  Google Scholar 

  20. Falcke, H. & Markoff, S. The jet model for Sgr A*: radio and X-ray spectrum. Astron. Astrophys. 362, 113–118 (2000).

    ADS  Google Scholar 

  21. Melia, F. An accreting black hole model for Sagittarius A*. II: A detailed study. Astrophys. J. 426, 577–585 (1994).

    ADS  Article  Google Scholar 

  22. Melia, F., Liu, S. & Coker, R. Polarized millimeter and submillimeter emission from Sagittarius A* at the Galactic center. Astrophys. J. 545, L117–L120 (2000).

    ADS  Article  Google Scholar 

  23. Rees, M. J. Tidal disruption of stars by black holes of 106–108 solar masses in nearby galaxies. Nature 333, 523–528 (1988).

    ADS  Article  Google Scholar 

  24. Haardt, F., Maraschi, L. & Ghisellini, G. X-ray variability and correlations in the two-phase disk-corona model for Seyfert galaxies. Astrophys. J. 476, 620–631 (1997).

    ADS  Article  Google Scholar 

  25. Tsuboi, M., Miyazaki, A. & Tsutsumi, T. in The Central Parsecs of the Galaxy (ed. Falcke, H. et al.) Vol. 186, 105–112 (ASP Conf. Ser., Astronomical Society of the Pacific, San Francisco, 1999).

    Google Scholar 

  26. Wright, M. C. H. & Backer, D. C. Flux density of Sagittarius A at λ = 3 millimeters. Astrophys. J. 417, 560–564 (1993).

    ADS  Article  Google Scholar 

  27. Serabyn, E. et al. High frequency measurements of the spectrum of SGR A*. Astrophys. J. 490, L77–L81 (1997).

    ADS  Article  Google Scholar 

  28. Falcke, H. et al. The simultaneous spectrum of Sagittarius A* from 20 centimeters to 1 millimeter and the nature of the millimeter excess. Astrophys. J. 499, 731–734 (1998).

    ADS  Article  Google Scholar 

  29. Zhao, J.-H., Bower, G. C. & Goss, W. M. Radio variability of Sagittarius A*—a 106 day cycle. Astrophys. J. 547, L29–L32 (2001).

    ADS  Article  Google Scholar 

  30. Reid, M. J. The distance to the center of the Galaxy. Annu. Rev. Astron. Astrophys. 31, 345–372 (1993).

    ADS  CAS  Article  Google Scholar 

Download references


We thank M. Begelman for useful comments. This work has been supported by a grant from NASA.

Author information

Authors and Affiliations


Corresponding author

Correspondence to F. K. Baganoff.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Baganoff, F., Bautz, M., Brandt, W. et al. Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre. Nature 413, 45–48 (2001).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

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.


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