RCW 120 is a nebula found 4,500 light years away in the constellation Scorpius. The ring of ionized gas is about ten light years across.
Bubbles such as RCW 120 are commonly found around O type stars throughout the Milky Way. The expanding bubble of gas in this nebula is causing the surrounding material to collapse, creating dense clumps where new stars may someday form.
Image from ESO, information from ESO and NASA.