Capturing the first-ever image of the Milky Way’s black hole was no easy task.
The historic image released Thursday, May 12, of what scientists call Sagittarius A*, took a planet-wide array of telescopes called the Event Horizon Telescope (EHT). The telescopes used atomic clock synchronization to merge their data precisely, which is no easy task given that the material around Sagittarius A* that the scientists were photographing changes shape every minute.
Although the result still seems hazy to a non-specialist, the scientists said it was because the collaboration was at the cutting edge of its capabilities.
“We are pushing our instrument to its limits here,” Michael Johnson, a member of the EHT team who is also an astrophysicist at Harvard and the Smithsonian, told reporters at a press conference Thursday. The image, he said, represents the “prettiest features he can see” because the telescope is at the diffraction limit, its resolution limit.
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“To get a sharper picture, we have to move our telescopes further away…or we have to go to higher frequencies,” Johnson said, adding, “We’re just at our breaking point here.”
And because the Event Horizon Telescope is already an Earth-sized array, getting its observatories farther apart is quite a challenge. Scientists have spoken of a network of space telescopes that could one day image black holes at greater distances from Earth’s orbit. But for today, the sharpness of the new Sagittarius A* image is the best possible for now given the amount of data involved.
Publicly available images also don’t reveal all the fine details of image resolution, added team member Katherine Bouman, a computer scientist at the California Institute of Technology.
The original data, worth about 3.5 petabytes (equivalent to 100 million TikTok videos, according to EHT), had to be compressed and modified to fit standard public distribution channels online and via the media. So much data was involved that EHT investigators had to send hard drives to each other for scientific work, rather than posting it on the Internet.
“This image is actually one of the sharpest images you’ve ever seen,” Bouman said. “It looks blurry on screen because we only see a few pixels, but in reality it’s one of the sharpest images ever.”