Light Echo

[Solarion]

A light echo is a phenomenon observed in astronomy. Analogous to an echo of sound, a light echo is produced when a sudden flash or burst of light, such as that observed in novae, is reflected off a source and arrives at the viewer after a considerably longer duration than it otherwise would have taken with a direct path. Because of their geometries, light echoes can produce the illusion of superluminal speeds.[1]

https://en.wikipedia.org/wiki/Light_echo

[video=youtube;ydfCP0c1Chc]https://www.youtube.com/watch?v=ydfCP0c1Chc[/video]