Capturing the first-ever image of the Milky Way’s black hole was no easy feat.
The historic image of what scientists are calling Sagittarius A* released Thursday (May 12) was taken by a planetwide set of telescopes called the Event Horizon Telescope (EHT). The telescopes used atomic clock time to precisely fuse their data, not an easy task given that the material around Sagittarius A* that the scientists photographed changes shape every minute.
While the result still seems blurry to a layperson, scientists said it was because the collaboration was at the limit of its capabilities.
“We’re pushing our instrument to the limit here,” Michael Johnson, an EHT team member and an astrophysicist from Harvard and Smithsonian, told reporters during a Thursday news conference. The image, he said, shows the “finest features it can see” because the telescope is at the diffraction limit, its limit of resolution.
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“To get a sharper image, we need to move our telescopes farther apart…or we need to go to higher frequencies,” Johnson said, adding, “We’re at our breaking point right now.”
And since the Event Horizon Telescope is already an Earth-sized array, getting its observatories further apart is quite a challenge. Scientists have talked about a space telescope array that could one day image black holes farther from Earth’s orbit. But for today, the sharpness of the new Sagittarius A* image is as good as we can make given the amount of data at the moment.
The 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 (the equivalent of 100 million TikTok videos according to EHT), had to be compressed and modified to fit the usual online and media public distribution channels. There was so much data involved that EHT investigators had to ship hard drives to each other for the research instead of streaming it over 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 it’s actually one of the sharpest images ever taken.”