Imagine two stars orbiting each other as they age. Toward the end of their lives their surfaces and atmospheres will grow and begin to merge into a common envelope. Explore how the age and gravitational potential of the system changes the shapes of the stars. You can explore the shape of the merged system by using the gravitational potential control which ignores the individual identities of the stars.
This simplified model shows the evolution of the individual stars to where they both reach the first Lagrange point (L1), which is the gravitationally neutral point between them. More complicated events, such as mass transfer or the merging of the stars, will occur beyond L1, but they are not represented by this Demonstration.