A Long Road

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The setbacks came early and often. Doeleman and his international colleagues began their first experiment in 2006, using a telescope in Arizona and another in Hawaii. They hoped to catch a glimpse of the Milky Way’s resident supermassive black hole, named Sagittarius A* (pronounced A-star). They got nothing for their exertions and spent months sifting through the data, trying to figure out what went wrong.“The worst part about not getting a detection is that you don’t know when to stop looking,” Doeleman said. After a long “sleuthing exercise,” the team realized there’d been a problem with one of the receivers. “A lot of endeavors don’t pan out until the second or third or fourth try,” he adds. “You have to be optimistic and confident that you are on the right path.”They tried the same experiment a year later, incorporating a third radio telescope in California. This time they succeeded, demonstrating the feasibility of the general approach. But they would need a much bigger array — including dishes in Mexico, Chile, Europe, and Antarctica — before they could have a realistic shot at obtaining a picture of a black hole.The EHT’s inaugural observing run took place in April 2017 with observations recorded and stored at eight geographically dispersed telescopes. Weather data collected each day from every site posed “an often-agonizing decision,” Doeleman reported. “Will the heavy clouds surrounding a mountaintop telescope dissipate, or will they settle in for the night? Is the weather risky at many sites, or maybe just one? And even if the sky above clears up, might ground conditions early in the evening leave a dish iced up and unusable?” In the end, the weather proved “overwhelmingly excellent,” he said, and they were able to observe five days out of a possible 10-day window.But that still wasn’t the end of the challenges. All of this data, stored on 960 computer hard drives, had to be combined, which meant physically connecting them. (You can’t just upload terabytes of data to the cloud.) This resulted in more lost time: The crates of hard drives shipped from Antarctica did not arrive until mid-December because the South Pole station closes during its winter months, from February to October, with no flights coming in or out.Add in all the time spent double- and triple-checking the numbers, and it’s what Doeleman has called “the ultimate in delayed gratification.” But after 20 years, the delay is finally over, and the EHT’s announcement can bring gratification to all the scientists and nonscientists alike who’ve ever wondered what a black hole actually looks like.