An Einstein Ring
Posted in Astronomy at 12:00 on 10 July 2022
How many galaxies can you see surrounding the galaxy cluster in the lower centre of this picture (taken from Astronomy Picture of the Day for 5/7/22?

Well, I agree the whole thing looks like a blob of liquid smeared across a surface through which light is shining but though it seems as if there are four very unusually shaped galaxies in the ring there is of course only one. Its light has been gravitationally lensed by the intervening galaxy cluster to form an Einstein ring.
