Secondary-to-primary mass ratio versus average separation

Secondary-to-primary mass ratio versus average separation (in units of the primary’s radius). The dashed box represents the known binary asteroids, the largest separation barely exceeds a secondary-to-primary mass ratio of 100. With equal mass and a separation that is more than 2,000 times the radius of each of its components, 2001 QW₃₂₂ (top right corner) is unique.