The material which fills the space between stars provides the raw materials for new stars to be born. It’s mostly hydrogen, some helium and a tiny amount of dust particles. Within the interstellar medium, there are clouds of varying densities that are rich in molecules like hydrogen and carbon monoxide. These molecularrich gas and dust clouds provide the ingredients that ultimately make up the building blocks of stars. In the densest regions of the interstellar medium, the core collapse of such a cloud can be triggered by a shock wave. These shock waves can be caused by a nearby supernova, by a collision with another molecular cloud or even by passing through the spiral arm of a galaxy, like our Milky Way. Such a shock wave can cause the rapid infall of the molecular material to produce the core of a new star, which continues to accrete as the star is born. These regions in the interstellar medium are stellar nurseries in the cosmos and are critical to the cycle of the life of a star.
Dr Emily Rickman, research fellow in astronomy at the European Space Agency