A black hole's secrets could hide in its dizzying light 'echoes' 

 Black hole light echoes are an extreme form of gravitational lensing. 

https://cdn.mos.cms.futurecdn.net/ynGm5uZScNiRXzRHcZrmn5.jpg

https://www.space.com/the-universe/black-holes/a-black-holes-secrets-could-hide-in-its-dizzying-light-echoes