It was just this year that we got our first real look at a black hole, and it matched many of the theoretical predictions that came before the Event Horizon Telescope (EHT) project made history. An impressive new NASA simulation shows us what that black hole might look like if we were closer.
A black hole pulls in all the matter and energy around it, so we can’t directly visualize the structure itself. However, we can see what it does to the space around it. What we’re looking at in the new NASA simulation is the accretion disk, the super-heated remnants of other objects as they fall into the black hole. Some aspects of the simulation don’t look right, but it’s all intentional. The physics of a black hole are just so extreme that it seems wrong.
The image depicts a black hole seen almost edge-on, with the accretion disk extending toward and away from the observer. The top and bottom humps aren’t really there — they’re the result of the black hole’s extreme gravity altering the path of light (a type of gravitational lensing). We’re actually seeing warped images of the top and bottom of the flat disk from the opposite side. This effect is most pronounced when looking at the black hole edge-on. You may also notice the left side of the disk looks brighter than the right, but that’s not a mistake. The glowing gas on the left is moving toward us, and Einstein predicted that would make it look brighter. Indeed, the EHT image showed the same effect.
According to NASA, the banding in the accretion disk comes from the churning magnetic field and the acceleration of matter near the event horizon. Gas nearest to the black hole orbits at almost the speed of light, but the outer areas move much slower. This stretches out the brighter sections, producing bands of light and dark. And what about that stationary bright line inside the main accretion disk? That’s the photon ring, a sort of “reflection” of the black hole’s accretion disk caused by photons that orbit very close to the event horizon two or three times before being thrown out where an observer can see them.
Inside the photon ring is the black hole “shadow,” which is about twice the size of the event horizon itself. Gravitational lensing and the capture of light makes this region pitch black. Anything that passes the event horizon is stuck there. Images like this help us visualize the extreme environment around a black hole, and we can be much more confident in their accuracy thanks to the EHT project.
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