This project called the Event Horizon Telescope, or EHT, refers to a point in space near a black hole where, no matter what you do, you’re going to fall in. We sometimes refer to this as the black hole’s radius. Because there is nothing to see at the event horizon, the EHT can’t detect it. It’s really black because not even light may escape from its perimeter.
The picture looks similar to the first EHT image of the supermassive black hole in M87’s center, which has a striking resemblance to this one. That black hole is approximately 1,500 times heavier and larger than Sgr A* and is roughly 2,000 light-years distant. It appears bigger than ours in the night sky.
The EHT image of the black hole in the center of M87 (left) compared to that in Sgr A* (right), shown to scale. The sizes of Mercury’s and Pluto’s orbits are also shown for comparison. Photo: EHT Collaboration
They are rather diverse. The M87 black hole is a lot larger than Sgr A*, and it would take material days and weeks to orbit it once, but matter around Sgr A* orbits in minutes. That makes imaging our local black hole much more difficult because the pictures must be taken considerably faster to avoid blurring the details. Many, many photographs were used to generate the picture of Sgr A* featured here, which shows an average of all of them together.