Editor's Summary

4 September 2008

Black hole physics: a new window on the Galactic Centre

Using Very Long Baseline Interferometry (VLBI) at the relatively short radio wavelength of 1.3 mm, a new intrinsic size estimate has been obtained for Sagittarius A*, the supermassive black hole candidate at the centre of the Milky Way. The resulting lower limit on the size of Sgr A* is less than the predicted size of the event horizon of the presumed black hole, suggesting that Sgr A* emissions centre not on the black hole itself but on the surrounding accretion flow. VLBI observations of the Galactic Centre at around 1.3 mm, less influenced by interstellar scattering than those made at longer wavelengths, open a new window onto black-hole physics that will become even more sensitive as new VLBI stations are built.

News and ViewsAstrophysics: Bringing black holes into focus

Do black holes exist? Observations at the finest resolution so far indicate that only gross deviations in the behaviour of gravity from that predicted by general relativity can invalidate the case that they do.

Christopher S. Reynolds


LetterEvent-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