The Black Hole Image That Needed Half a Ton of Hard Drives

The first black hole image used about 5 petabytes of data, filling over half a ton of hard drives, and some of it was faster to fly than send online.

Astronomy

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In 2019, the Event Horizon Telescope produced the first image of a black hole, targeting the supermassive black hole at the center of the galaxy M87. The achievement was not a normal snapshot from one telescope. Radio telescopes around the world observed at the same time and worked together as an Earth-sized virtual telescope. Their recordings produced roughly 5 petabytes of raw data, enough to fill more than half a ton of hard drives. The data was then taken to specialized processing centers, where it was combined and analyzed to produce an image only a few hundred kilobytes in size. The unusual part was how some of that enormous data set was transported. For data from Hawaii, the article estimated that about 700 terabytes could be moved from the observing site to the MIT Haystack facility in roughly 14 hours, including ground travel and a flight. That works out to about 14 gigabytes per second. For such a huge one-way transfer, physically moving storage could beat sending the same amount through ordinary internet connections. The project also had to wait for Antarctic summer before data recorded at the South Pole could be transported out. The resulting picture is not a conventional photograph of the black hole itself. It shows the dark shadow produced by the black hole against glowing material around it. The 2019 observation became possible because widely separated radio telescopes were synchronized and their recordings later combined computationally. The result provided direct visual evidence of the shadow of the supermassive black hole in M87, about 55 million light-years away and roughly 6.5 billion times the mass of the Sun.

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