解説Binary star system - semidetached configuration q=1.svg
English: Schematic of a binary star system in a semidetached configuration with a mass ratio q=1, viewed at an inclination of 90 degrees (edge on). The filled regions represent the two stars. The black line represents the inner critical Roche equipotential, made up of two Roche lobes that meet at the Lagrangian point L1. In a semidetached configuration one star fills its Roche lobe.