Testing General Relativity with the Event Horizon Telescope
Abstract
General relativity (GR) predicts that light near a black hole will be lensed so as to produce a nearly circular photon orbit at a well-defined radius around the black hole. When embedded in an accretion flow, the emission profile will resemble all or part of a ring with a dark "shadow" within the photon orbit. Detecting the size and shape of a black hole shadow would serve as a test of GR. In particular, significant deviation from circular symmetry of the photon orbit would violate the "no-hair" theorem of GR. However, these observations have heretofore not been possible due to the very small angular size of the shadow as seen from Earth. The Event Horizon Telescope (EHT) is an array of millimeter-wavelength telescopes operating as a very long baseline interferometer (VLBI) array to observe nearby supermassive black holes at extremely high angular resolution. The EHT will be able to resolve the shadow of the Galactic Center black hole Sgr A*. We explore through simulations the traction that data from the EHT will have in extracting the size of the shadow in Sgr A*, and in particular the ability of long sensitive baselines to the phased ALMA array to determine the asymmetry of the black hole shadow. Our investigations demonstrate that millimeter-wavelength VLBI observations can provide new probes of GR in the strong-field regime. This work is funded by grants from the National Science Foundation.
- Publication:
-
American Astronomical Society Meeting Abstracts #218
- Pub Date:
- May 2011
- Bibcode:
- 2011AAS...21822907R