The Event Horizon Telescope (EHT) is an initiative to use Radio Telescopes around the world to study the Supermassive Black Hole, Sagittarius A* at the Galactic Center of the Milky Way, using Very-long-baseline Interferometry, with the goal of resolving the Black Hole's event horizon. A second black hole, at the center of M87 is also a target. Images are collected once a year when the geometry is right to view the targets. The goal is baselines in multiple directions on the order of 12000km, as large as can be done from the ground, and appropriate telescopes are recruited toward reaching this goal. The first image was taken in 2006.
Very-long-baseline Interferometry (VLBI)