https://www.nytimes.com/2018/10/04/magazine/how-do-you-take-...
The author, Seth Fletcher, also wrote a book about it, "Einstein's Shadow: A Black Hole, a Band of Astronomers, and the Quest to See the Unseeable", if you want more details.
https://www.goodreads.com/book/show/36300597-einstein-s-shad...