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Doeleman and his colleagues were hoping the giant flashlight would reveal a ring of light known as the last photon orbit. The closest light can get to a black hole without being “eaten,” that orbit is the result of photons being flung off from the super-heated material around the black hole. Some of those photons are redirected by the extreme gravity and come to Earth, where they could be detected by EHT researchers.

“To do this, we worked for over a decade,” Doeleman said, in a Washington, D.C., press conference attended by media from around the globe. “In April 2017, all the dishes in the Event Horizon Telescope turned and stared at a galaxy 55 million light years away called M87 and the supermassive black hole at its core, and we are delighted to be able to report to you today that we have seen what we thought was unseeable. We have seen and taken a picture of a black hole.”

The image, revealed by Doeleman, prompted a large round of applause from onlookers and praise from other scientists who attended the event.

“[This announcement] will transform and enhance our understanding of black holes,” said National Science Foundation Director France Córdova. “As an astrophysicist, this is a thrilling day for me.

“Black holes have captivated the imaginations of scientists and the public for decades. We have been studying black holes for so long, sometimes it’s easy to forget that none of us has actually seen one,” she continued. “I believe [this image] will demonstrate an imprint on people’s memories — the Event Horizon Project shows the power of collaboration, convergence, and shared resources, allowing us to tackle the universe’s biggest mysteries.”

“Today general relativity has passed another crucial test, one spanning from the horizons to the stars.” Avery Broderick, professor of physics and astronomy at the University of Waterloo

Avery Broderick, a professor of physics and astronomy at the University of Waterloo and a member of the Perimeter Institute for Theoretical Physics, said the image provided a key confirmation of Einstein’s theories.

“Every photon in these first EHT images began its journey in a churning maelstrom embedded in the most extreme environment in the universe — the vicinity of a black hole,” he said. “The radio waves we see in these first images orbited a black hole before beginning their 55 million–year journey toward us, and this results in the black shadow or silhouette cast by the event horizon.

“General relativity makes a clear prediction of both the size and shape of those features — the shadow should be circular,” he continued. “However, as with all journeys of discovery, when we began this expedition of the mind, we did not know what we would find. Were Einstein wrong or the object at the heart of M87 not a black hole, its silhouette could have been very different … or simply missing. But in April 2017, this was the dog that did not bark. The shadow exists, and today general relativity has passed another crucial test, one spanning from the horizons to the stars.”

But the only way to detect black holes, Doeleman said, was through VLBI, or very long baseline interferometry. The process involves collecting data from multiple radio telescopes around the globe, then using algorithms and supercomputers to analyze that data, effectively creating a “virtual telescope” the size of the Earth itself, turning the planet into a giant radio telescope.

Such telescopes work by using parabolic dishes to bounce signals to a central focal point, allowing astronomers to create an image. But the EHT team had to get multiple telescopes around the world to work together. In smaller telescope arrays, that process is simple — the dishes can simply be tied together with cables that run between them. When working on a planetary scale, though, those direct connections aren’t possible.