======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@mpifr-bonn.mpg.de http://www.mpifr-bonn.mpg.de/gcnews ======================================================================== Vol. 11, No. 1 Dec 14, 1999 Recently submitted papers: -------------------------- Email : hfalcke@mpifr-bonn.mpg.de Title : Viewing the Shadow of the Black Hole at the Galactic Center Author(s): Heino Falcke(1), Fulvio Melia(2), and Eric Agol(3) Institute: (1) Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121, Bonn, Germany (2) Physics Department and Steward Observatory, The University of Arizona, Tucson, AZ 85721 (3) Physics and Astronomy Department, Johns Hopkins University, Baltimore, MD 21218. Paper : ApJ 528, L13 (Jan 1, 2000) Weblink : http://www.aoc.nrao.edu/staff/hfalcke/publications.html#bhimage EPrint : astro-ph/9912263 Abstract: In recent years, the evidence for the existence of an ultra-compact concentration of dark mass associated with the radio source Sgr A* in the Galactic Center has become very strong. However, an unambiguous proof that this object is indeed a black hole is still lacking. A defining characteristic of a black hole is the event horizon. To a distant observer, the event horizon casts a relatively large ``shadow'' with an apparent diameter of ~10 gravitational radii due to bending of light by the black hole, nearly independent of the black hole spin or orientation. The predicted size (~30 micro-arcseconds) of this shadow for Sgr A* approaches the resolution of current radio-interferometers. If the black hole is maximally spinning and viewed edge-on, then the shadow will be offset by ~8 micro-arcseconds from the center of mass, and will be slightly flattened on one side. Taking into account scatter-broadening of the image in the interstellar medium and the finite achievable telescope resolution, we show that the shadow of Sgr A* may be observable with very long-baseline interferometry at sub-millimeter wavelengths, assuming that the accretion flow is optically thin in this region of the spectrum. Hence, there exists a realistic expectation of imaging the event horizon of a black hole within the next few years. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke (cotera@ipac.caltech.edu) (hfalcke@mpifr-bonn.mpg.de) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@mpifr-bonn.mpg.de ========================================================================