RCW 120 is one such nebula, located over 4000 light years away in the constellation of Scorpius. Several stars are in the process of being born here; look right in the center and you'll see a blue speck; that's a star that's already far larger and more powerful than the Sun. It floods the nebula with ultraviolet light and blows out a mighty solar wind that's compressing the gas around it, forming the bubble shape of the overall cloud. Other stars are forming around the rim of the bubble, and one of them is already massive enough that its fate is sealed: one day, million of years from now, it will explode. So will the star in the center, in fact, though it's unknown which will blow its top first.