Some years ago, I remember reading a news article where someone was looking at the remnant of a supernova, noticed that there was a massive gas cloud some lightyears away from the remnant, realized that given the age of the gas cloud and its distance from the remnant and Earth meant that it would be possible for us to see the reflection of the supernova in the light coming from the gas cloud of the supernova explosion. So, I was reminded of that when I read this article. Just incredible that we can do something like that.