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.

On the size of the galactic centre compact radio source: diameter <20 AU

Abstract

The existence of a compact nonthermal radio source at the galactic centre was first suggested by Lynden-Bell and Rees1 as the possible signature of a black hole. Such a source was detected unambiguously by Balick and Brown2.Very long baseline interferometry (VLBI) observations of the structure of this source, hereafter referred to as Sgr A*, have been made for several years3,4. In all previous experiments, the visibility amplitudes, measured over a restricted (U, V) range, could be fitted only to the simplest model of brightness distribution, that is, to a circular gaussian. We have re-observed Sgr A* at λ3.6 cm and λ 1.35 cm with many baselines, using the more sensitive receivers and VLBI recording terminals now available. These observations set an upper limit of 20 AU (3 × l014 cm) to the diameter of Sgr A* at λ 1.35 cm and reveal for the first time an elongated structure at λ 3.6 cm, with the position angle of the long axis almost parallel to the rotation axis of the Galaxy. Sgr A* is unique in our Galaxy, but resembles most closely the compact radio sources at the centre of external galaxies. Observations of the central 4 arc s (0.2 pc) at radio and other wavelengths are best explained by a single massive collapsed object at the galactic centre.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1

    Lynden-Bell, D. & Rees, M. J. Mon. Not. R. astr. Soc. 152, 461–475 (1971).

    ADS  Article  Google Scholar 

  2. 2

    Balick, B. & Brown, R. L. Astrophys. J. 194, 265–270 (1974).

    ADS  Article  Google Scholar 

  3. 3

    Lo, K. Y., Cohen, M. H., Readhead, A. C. S. & Backer, D. C. Astrophys. J. 249, 504–512 (1981).

    ADS  CAS  Article  Google Scholar 

  4. 4

    Kellermann, K. I., Sahaffer, D. B., Clark, B. G. & Geldzahler, B. G. Astrophys. J. Lett. 214, L61–L62 (1977).

    ADS  Article  Google Scholar 

  5. 5

    Rogers, A. E. E. et al. Science 219, 51–54 (1983).

    ADS  CAS  Article  Google Scholar 

  6. 6

    Lo, K. Y. IAU Symp. 110, 265–273 (1984).

    ADS  Google Scholar 

  7. 7

    Marcaide, J. M. et al. in Conference on Active Galactic Nuclei (ed. Dyson, J. E.) (Manchester University Press, in the press).

  8. 8

    Brown, R. L., Lo, K. Y. & Johnston, K. J. Astr. J. 83, 1594–1597 (1975).

    ADS  Article  Google Scholar 

  9. 9

    Davies, R. D., Walsh, D. & Booth, R. Mon. Not. R. astr. Soc. 177, 319–333 (1976).

    ADS  Article  Google Scholar 

  10. 10

    Higdon, J. C. Astrophys. J. 285, 109–123 (1984).

    ADS  CAS  Article  Google Scholar 

  11. 11

    Cordes, J. M., Ananthakrishnan, S. & Dennison, B. Nature 309, 689–690 (1984).

    ADS  Article  Google Scholar 

  12. 12

    Kellermann, K. I. & Pauliny-Toth, I. I. K. A. Rev. Astr. Astrophys. 19, 373–410 (1984).

    ADS  Article  Google Scholar 

  13. 13

    Reynolds, S. P. & McKee, C. F. Astrophys. J. 239, 893–897 (1980).

    ADS  CAS  Article  Google Scholar 

  14. 14

    Bartel, et al. Astrophys. J. 262, 556–563 (1982).

    ADS  CAS  Article  Google Scholar 

  15. 15

    Hummel, E., van der Hulst, J. M. & Dickey, J. Astr. Astrophys. 134, 207–221 (1985).

    ADS  Google Scholar 

  16. 16

    Sofue, Y. & Handa, T. Nature 310, 568–569 (1984).

    ADS  Article  Google Scholar 

  17. 17

    Yusef-Zadeh, F., Morris, M. & Chance, D. Nature 310, 557–561 (1984).

    ADS  Article  Google Scholar 

  18. 18

    Lo, K. Y. & Claussen, M. J. Nature 306, 647–651 (1983).

    ADS  CAS  Article  Google Scholar 

  19. 19

    Ekers, R. D., van Gorkom, J., Schwarz, U. J. & Goss, M. W. Astr. Astrophys. 122, 143–150 (1983).

    ADS  CAS  Google Scholar 

  20. 20

    Becklin, E., Gatley, I. & Werner, M. Astrophys. J. 258, 135–142 (1982).

    ADS  CAS  Article  Google Scholar 

  21. 21

    Lacy, J. H., Townes, C. H. & Hollenbach, D. J. Astrophys. J. 262, 120–134 (1982).

    ADS  CAS  Article  Google Scholar 

  22. 22

    Henry, J. P., Depoy, D. L. & Becklin, E. E. Astrophys. J. Lett. 285, L27–L30 (1984).

    ADS  CAS  Article  Google Scholar 

  23. 23

    Hall, D. N. B., Kleinman, S. G. & Scoville, N. Z. Astrophys. J. Lett. 262, L53–L58 (1982).

    ADS  Article  Google Scholar 

  24. 24

    Geballe, T. R. et al. Astrophys. J. 284, 118–125 (1984).

    ADS  CAS  Article  Google Scholar 

  25. 25

    Ramaty, R. & Lingenfelter, R. E. Highlights of Astronomy 6, 525–529 (1983).

    ADS  Article  Google Scholar 

  26. 26

    Rieke, G. & Lebofsky, M. J. AIP Conf. Proc. 83, 194–203 (1982).

    ADS  CAS  Article  Google Scholar 

  27. 27

    Rees, M. AIP Conf. Proc. 83, 166–176 (1982).

    ADS  CAS  Article  Google Scholar 

  28. 28

    Brown, R. L. & Lo, K. Y. Astrophys. J. 253, 108–114 (1982).

    ADS  Article  Google Scholar 

  29. 29

    Backer, D. C. IAU Symp. 97, 389–390 (1982).

    ADS  Google Scholar 

Download references

Author information

Affiliations

Authors

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Lo, K., Backer, D., Ekers, R. et al. On the size of the galactic centre compact radio source: diameter <20 AU. Nature 315, 124–126 (1985). https://doi.org/10.1038/315124a0

Download citation

Further reading

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