Calculations of the formation of non-equal mass binary and multiple systems are presented. Binary formation results from the elongated shape of the initial cloud, one fragment forming on each side of the equatorial plane. Slight linear density gradients along the cloud’s major axis are sufficient to form non-equal mass fragments. Resultant mass ratios range from 0.1 to 1.0, in agreement with observations.

In the presence of rotation, the fragments form with surrounding disks. The primary forms with a larger disk than does the secondary. Due to it’s orbital motion around the primary, the secondary can directly accrete the matter that has gathered in the primary’s disk. The secondary is thus less likely to have an appreciable disk, accounting for a redder primary. The binary system’s initially high eccentricity decreases with the continued accretion of higher specific angular momentum at apastron and lower specific angular momentum matter at periastron. Non-coplanar multiple systems with unequal mass components are also formed. The systems are composed of an inner binary and a more distant companion. The mass ratio of the companion binary system is usually less than that of the binary.