I recently read an article that said that the event horizon telescope took a picture of a black hole (Sagitarius A*) and it will be presented on the 10th of April. I was wondering how this picture is taken and what a picture of a black hole even means?
The only explanation I could think of was that the telescope took pictures of the stars surrounding the black hole and then a sudden absence of stars pointed that a black hole is present.
Can anyone explain how black hole photos are taken or how does event horizon telescope work?