“Researchers at the Event Horizon Telescope project say they were able to create an image of a black hole by using a network of eight radio telescopes to create “a virtual telescope dish as large as the Earth itself,” the National Science Foundation says.
The breakthrough, Doeleman said, came after a decade of work to align the myriad working parts of the project and gain the highest resolution possible from the Earth’s surface. Finally, in April of 2017, he said, “all of the dishes in the Event Horizon Telescope swiveled, turned and stared” at the core of M87. From that data came the image that was released Wednesday.”
See also: XKCD: M87 Black Hole Size Comparison.