Google “Odd Radio Circles – ORCs” , the net is filled with articles and pictures.

A new discovery by radio astronomers over just the last few months has started to reveal mysterious circular objects at immense extragalactic distances, visible only at radio wavelengths. They seem to be centered on very distant galaxies. Explosion features?
Gravitational Lensing Artifacts? Deep Space Crop Circles? The mother of all industrial accidents?

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

http://www.sci-news.com/astronomy/odd-radio-circles-08632.html

“Anything which is not forbidden is mandatory.”