You've heard of a sound echo: Sound bounces off of a surface and reflects back, causing a delay.

Did you know that light echos are also a thing? If there is a flash of light from something like a supernova, that light can hit interstellar clouds of dust and then reflect back, giving you light from the original supernova but on a delay.

We can use this delayed light to learn about what kind of star blew up in the supernova.

🎞️ https://www.spitzer.caltech.edu/video/ssc2008-09v2-dissecting-a-light-echo

#astronomy #space