The formation of a star starts with gravitational instability inside of a molecular cloud, because of areas of better density—often activated by compression of clouds by radiation from large stars, growing bubbles within the interstellar medium, the collision of different molecular clouds, or perhaps the collision of galaxies (as in https://bydatto3rangekm04714.free-blogz.com/83380512/new-step-by-step-map-for-star