Building a Refinery at L5
From the National Aeronotics and Space Administration [NASA] web site we learn:
The Itallian-French mathematician Joseph Lagrange discovered five points in the vicinity of two orbiting masses where a third, smaller mass can orbit at a fixed distance from the larger masses. More precisley, the Lagrange Points mark positions where the gravitational pull of the two large masses prcisely cancels the centripital acceleeration required to rrotate with them. Of the five Lagrange points, three are unstable and two are stable. The unstable Lagrange points - labelled L1, L2 and L3 - lie along the line connecting the two large masses. The stable Lagrange points - labeled L4 and L5 - form the apex of two equilateral triangles that have the large masses at their vertices.