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.

  • News & Views
  • Published:

Astronomy

Galactic rotation in real time

Nature volume 407, pages 307–309 (2000)Cite this article

On page 349 of this issue, Andrea Ghez and colleagues1 present the first measurements of the acceleration of stars orbiting the nucleus of our Galaxy. These stars are part of a dense cluster associated with the compact radio source known as Sagittarius A*, which is thought to be at the actual centre of the Milky Way. Measuring the accelerations of stars in galactic orbits (and not just their velocities) is a technical tour de force. These accelerations are enormous on a Galactic scale; at 3–6 mm s−2 they are comparable to those experienced by the Earth as it orbits the Sun. With these measurements, the authors help to identify Sagittarius A* as the supermassive black hole at the centre of the Milky Way. They also test — and provide support for — fundamental assumptions about the dynamics of the Galactic centre and our understanding of violent activity in galactic nuclei.

Ghez et al.1 took a series of infrared images of the nucleus of the Milky Way with the 10-metre Keck telescope on Mauna Kea, Hawaii. The Galactic centre is 8 kiloparsecs away (1 parsec=3.26 light years) and Ghez et al. study an area 0.2 parsecs across. By taking short exposures they freeze the jitter in the image caused by turbulence in the Earth's atmosphere and produce images with 0.05 arcsec (0.002 parsecs) resolution. From such an image, one can accurately determine stellar positions. The stars nearest the centre move significantly in just a few years, so Ghez et al. can measure the two components of their velocities that are in the plane of the sky. If the central star cluster is in equilibrium, then its dynamics tell us the total mass enclosed inside it.

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

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

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

Figure 1: Infrared image of the Sagittarius (Sgr) A* star cluster taken in May 1999.

References

  1. Ghez, A. M., Morris, M., Becklin, E. E., Tanner, A. & Kremenek, T. Nature 407, 349–351 (2000).

    Article  ADS  CAS  Google Scholar 

  2. Eckart, A. & Genzel, R. Mon. Not. R. Astron. Soc. 284, 576–598 (1997).

    Article  ADS  Google Scholar 

  3. Genzel, R., Eckart, A., Ott, T. & Eisenhauer, F. Mon. Not. R. Astron. Soc. 291, 219–234 (1997).

    Article  ADS  Google Scholar 

  4. Genzel, R., Pichon, C., Eckart, A., Gerhard, O. E. & Ott, T. http://xxx.lanl.gov/abs/astro-ph/0001428

  5. Ghez, A. M., Klein, B. L., Morris, M. & Becklin, E. E. Astrophys. J. 509, 678–686 ( 1998).

    Article  ADS  Google Scholar 

  6. Lo, K. Y., Shen, Z.-Q, Zhao, J.-H & Ho, P. T. P. Astrophys. J. 508, L61–L64 (1998).

  7. Narayan, R., Mahadevan, R. & Quataert, E. in The Theory of Black Hole Accretion Discs (eds Abramowicz, M. A., Björnsson, G. & Pringle, J. E.) 148– 182 (Cambridge Univ. Press, 1998).

    Google Scholar 

  8. Rees, M. J. Annu. Rev. Astr. Astrophys. 22, 471– 506 (1984).

    Article  ADS  CAS  Google Scholar 

  9. Blandford, R. D. in Active Galactic Nuclei: Saas-Fee Course 20 (eds Courvoisier, T. J.-L & Mayor, M.) 161–275 (Springer, Berlin, 1990).

    Google Scholar 

  10. Maoz, E. Astrophys. J. 494, L181–L184 (1998 ).

  11. Tsiklauri, D. & Viollier, R. D. Astrophys. J. 500 , 591–595 (1998).

    Article  ADS  CAS  Google Scholar 

  12. Munyaneza, F., Tsiklauri, D. & Viollier, R. D. Astrophys. J. 526, 744– 751 (1999).

    Article  ADS  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Department of Astronomy University of Texas at Austin, RLM 15.308, Austin , 78712, Texas, USA

    John Kormendy

Authors
  1. John Kormendy
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to John Kormendy.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Kormendy, J. Galactic rotation in real time. Nature 407, 307–309 (2000). https://doi.org/10.1038/35030274

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1038/35030274

Search

Advanced 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