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Event Horizon Telescope

Project Summary:

A long standing goal in astrophysics is to directly observe the immediate environment of a putative black hole with angular resolution comparable to the event horizon. Realizing this goal would open a new window on the study of General Relativity in the strong field regime, accretion and outflow processes at the edge of a black hole, the existence of an event horizon, and fundamental black hole physics. Steady long-term progress on improving the capability of Very Long Baseline Interferometry (VLBI) at short wavelengths has now made it extremely likely that this goal will be achieved within the next decade. The most compelling evidence for this is the recent observation by 1.3mm VLBI of Schwarzschild radius scale structure in SgrA*, the compact source of radio, submm, NIR and xrays at the center of the Milky Way. SgrA* is thought to mark the position of a ~4 million solar mass black hole, and because of its proximity and estimated mass presents the largest apparent event horizon size of any black hole candidate in the Universe. This new 1.3mm VLBI detection confirms that short wavelength VLBI of SgrA* can and will be used to directly probe the Event Horizon of this black hole candidate: in short, SgrA* is the right object, VLBI is the right technique, and this decade is the right time. Over the next decade, our group proposes to combine existing and planned mm/submm facilities into a high sensitivity, high angular resolution "Event Horizon Telescope" that will bring us as close to the edge of black hole as we will ever come. This effort will include development and deployment of submm dual polarization receivers, highly stable frequency standards to enable VLBI at 230-450GHz, higher bandwidth VLBI backends and recorders, as well as commissioning of new submm VLBI sites. We emphasize that while there is development and procurement involved, the path forward is clear and the recent successful observations have removed much of the risk that would normally be associated with such an ambitious project.

Contributing Institutes:

MIT Haystack Observatory

Arizona Radio Observatory - University of Arizona

Harvard-Smithsonian Center for Astrophysics

UC Berkeley Radio Astronomy Laboratory

Joint Astronomy Centre - James Clerk Maxwell Telescope

Caltech Submillimeter Observatory

Combined Array for Research in Millimeter-wave Astronomy

Max Planck Institut fuer Radioastronomie

National Astronomical Observatory of Japan

Institut de Radio Astronomie Millimetrique

National Radio Astronomy Observatory

Academia Sinica Institute for Astronomy and Astrophysics

Large Millimeter Telescope