Near the top he shows two photos of the Cartwheel galaxy, one from 2014 and one from 2021 with the caption:
> Can you spot Supernova 2021 axdf?
Are you supposed to be able to spot the supernova?
All I've noticed is a couple of small stars that disappear in the latter photo, but this mostly seems to be because it's more blurry.
Use the cross-eye trick to superimpose the two pictures, then it becomes quickly noticeable as it will appear to blink.
Bottom-left corner