Sagittarius A* in pictures: First photo of the Milky Way’s monstrous black hole explained in pictures

The EHT collaboration has created possible images of Sagittarius A* using ray tracing, which predicts what black holes look like, based on Einstein’s general theory of relativity.

(Image credit: Ben Prather/EHT Theory Working Group/Chi-Kwan Chan)

To understand the bizarre environmental physics of Sgr A*, the imaging team used tools and models to measure the observed properties. They also developed more simplified models “that we can directly map to the EHT data,” Harvard and Smithsonian astrophysicist Michael Johnson told reporters after the black hole image was announced on May 12, 2022.

“It’s a different approach than visualization,” Johnson said. “It gives us a different perspective and allows us to understand the biases of both methods because these simple models are easier to constrain to very limited data.”

There were two ways to work with models. The first was to split the data over time and match them with snapshots of the black hole in action to make sure the measurements weren’t “contaminated” by environmental variability. This was combined into a single averaged model.

The second model sought to fit all the data at the same time. “Here we come to the average structure of the image, as well as an additional source of noise variability that sits on top of that average,” Johnson said. “This procedure is very similar to what we did to create images. By combining all these different approaches, we were able to accurately characterize the properties of the ring.”

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