How do photon rings in black holes help scientists study these cosmic objects?

Photon rings in black holes serve as valuable tools for scientists studying the properties of these cosmic phenomena. Similar to how examining tree branches helps understand a tree's structure, these rings provide insights into the black hole's characteristics and behavior. The series of photon rings, or subrings, function like frames in a movie, each capturing a moment in the history of the visible universe as observed from the black hole's perspective. Together, these rings create a chronological record that allows scientists to piece together information about both the black hole itself and the surrounding cosmos, offering a unique window into the universe's past and present.