The Evolution of an OB Association

The Evolution of an OB Association
High-speed particles and ultraviolet radiation from young O and B stars produce a shock wave that compresses gas farther into the molecular
cloud, stimulating new star formation deeper in the cloud. Meanwhile, older stars are left behind. Inset: Stars forming around a massive star
2500 ly (770 pc) away in the constellation Monoceros’s Cone Nebula. The stars (small dots on the right side of the inset) arrayed around the
bright, massive central star are believed to have formed as a result of the central star compressing surrounding gas with high-speed particles
and radiation. The younger stars are just 0.04–0.08 ly from the central star