September 30, 2022

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Sagittarius A*: The first image of the Milky Way's black hole in the images

Sagittarius A*: The first image of the Milky Way’s black hole in the images

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

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

To understand the strange physics of Sgr A*’s environment, the imaging team used tools and models to measure the observed properties. They’ve also developed simpler models that “we can fit directly into the EHT data,” Michael Johnson, an astrophysicist at Harvard and Smithsonian University, told reporters after announcing the black hole imagery on May 12, 2022.

“This is a different approach from photography,” Johnson said. “It gives us a different perspective, and it allows us to understand the methodological biases of both methods because these simple models are easy to constrain with very limited data.”

There were two methods they worked with models. The first was splitting the data by time and adapting it to snapshots of the black hole in action, to ensure that the measurements were not “polluted” by the diversity in their environment. This is combined into one average checkout form.

The second model sought to contain all the data at the same time. “Here, we fit the average image structure, along with an additional source of contrast noise sitting on top of that average,” Johnson said. “This procedure is very similar to what we did to make the images. By combining all of these different approaches, we were able to accurately characterize the ring.”

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