Star merger created rare Blue Ring Nebula

Astronomers were surprised when they discovered what appeared to be a star surrounded by an ultraviolet ring 16 years ago. It became known as the Blue Ring Nebula, located 6,300 light-years away from Earth in the Hercules constellation.

source https://www.cnn.com/2020/11/18/world/blue-ring-nebula-star-merger-scn-trnd/index.html