Why do many stars form in pairs or larger groups?

Stars form in pairs or larger groups because they are born from the gravitational collapse of dense clumps within molecular clouds.12

During the formation process, a collapsing cloud typically possesses a rotary motion derived from the original movement of the material falling into it. As this cloud shrinks, it flattens due to its spin, and most of its mass concentrates into a rotating central condensation known as a protostar. This central region is often destined to become one or more closely spaced stars.2

Depending on the efficiency of star formation and the amount of matter involved, these stars may remain bound to one another as a cluster or disperse into an unbound association. Because of this common formation mechanism, it is estimated that more than half of all stars in the Milky Way Galaxy exist as members of binary star systems or more complex multiple-star groups.134