Astronomers linked four telescopes in Califoirnia, Arizona, and Hawaii, to create a single more powerful radio telescope to improve our measures of black holes. They did so by focusing on galaxy of M87 (see image below), which has a massive black hole 6.2 billion times the Sun. From my Nature article, “Closest look yet at a distant black hole”:
The telescope enabled astronomer Sheperd Doeleman of the MIT Haystack Observatory in Westford, Massachusetts, and his colleagues to determine that the high-speed particle jet shooting from the core of M87 originates within a region that is just 5.5 times larger than the estimated radius, or event horizon, of the black hole — the first time scientists have made such a measurement.
By 2015, Doeleman and his colleagues hope to double the resolution of their observation by adding 20 or so radio dishes from ALMA, the giant radio array now being built in Chile’s Atacama desert. With ALMA, says Doeleman, the telescope network will have the sensitivity to make bona fide images of the region surrounding a supermassive black hole and search for a black hole’s shadow — a predicted feature in which light from a black hole jet headed away from Earth gets bent into a bright ring that may be visible.