We now have images of the environment at a black hole’s event horizon

Enlarge / The first image of the environment around a black hole. As a matter of fact, it's not all dark. (credit: National Science Foundation)

Two years ago, telescopes around the world turned their attention to two supermassive black holes. Now, after a massive computational effort, their data has been combined in a way that allowed them to function as a single, Earth-sized telescope. The results are an unprecedented glimpse of the environment around supermassive black holes, and they confirm that relativity still works under the most extreme gravitational forces.

The environment near the black hole appears to change on very short time scales, though we're not sure about the significance of this. White circles reflect the resolving power of the Event Horizon Telescope. (credit: Astrophysical Journal)

The black hole in question is a supermassive one at the center of the galaxy M87, 55 million light years away. M87 is an active galaxy where the black hole is feeding on matter and ejecting jets of material. The image is made from photons that were temporarily trapped in orbit around the black hole. Here, the intense gravity causes matter-and even space itself-to move at approximately the speed of light. The eventual escape of these photons causes a bright ring to appear around the black hole itself, with the details of the ring reflecting the physics of the black hole.

At a press conference this morning, Avery Broderick of the Perimeter Institute described what the images tell us. One key finding is that the object is a black hole, at least as we've understood black holes using relativity. It does not have any visible surface, and the "shadow" of light it creates is circular within the limits of our observations. We can also tell that it spins clockwise. All of the properties we can infer from these images are consistent with relativity. "I was a little stunned that it matched the predictions we made so well," said Broderick.

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