Volume 455 Number 07245 pp78-80
Event-horizon-scale structure in the
supermassive black hole candidate at the Galactic Centre
Sheperd S. Doeleman, Jonathan Weintroub, Alan E. E. Rogers,
Richard Plambeck, Robert Freund, Remo P. J. Tilanus, Per Friberg, Lucy M.
Ziurys, James M. Moran, Brian Corey, Ken H. Young, Daniel L. Smythe, Michael
Titus, Daniel P. Marrone, Roger J. Cappallo, Douglas C.-J. Bock, Geoffrey C.
Bower, Richard Chamberlin, Gary R. Davis, Thomas P. Krichbaum, James Lamb, Holly
Maness, Arthur E. Niell, Alan Roy, Peter Strittmatter, Daniel Werthimer, Alan R.
Whitney & David Woody
The cores of most galaxies are thought to
harbour supermassive black holes, which power galactic nuclei by converting
the gravitational energy of accreting matter into radiation. Sagittarius A*
(Sgr A*), the compact source of radio, infrared and X-ray emission at the
centre of the Milky Way, is the closest example of this phenomenon, with an
estimated black hole mass that is 4,000,000 times that of the Sun. A
long-standing astronomical goal is to resolve structures in the innermost
accretion flow surrounding Sgr A*, where strong gravitational fields will
distort the appearance of radiation emitted near the black hole. Radio
observations at wavelengths of 3.5 mm and 7 mm have detected intrinsic
structure in Sgr A*, but the spatial resolution of observations at these
wavelengths is limited by interstellar scattering. Here we report
observations at a wavelength of 1.3 mm that set a size of 37 +16
/ -10 microarcseconds on the intrinsic diameter of Sgr A*. This
is less than the expected apparent size of the event horizon of the presumed
black hole, suggesting that the bulk of Sgr A* emission may not be centred
on the black hole, but arises in the surrounding accretion flow.
From the September 4th edition of Nature:
- Letters: "Event-horizon-scale structure in the
supermassive black hole candidate at the Galactic Centre"
- News and Views: "Astrophysics: Bringing black holes into focus"
- Editor's Summary: "Black hole physics: a new window on the Galactic