Lagrange Points (or L-points) recently came into the limelight during the launch of the James Webb Space Telescope (JWST). Named after the famous mathematician Joseph-Louis Lagrange, these are special points in space where the net gravitational forces of the earth and the sun (or to generalize, those of any two bodies with large masses) are roughly equal. This gravitational equilibrium creates a more or less stable orbital mechanism due to which objects with small masses can steadily orbit around the sun along with the earth.

This is based on the three-body-problem in classical mechanics. In general, two large bodies exert unbalanced gravitational forces on any small body between the two, often altering the orbit of the third body. However, at these L-points, the centrifugal force balances out the gravitational forces of the two large bodies, thus ensuring a much smoother orbital path for the smaller body. As a result, these L-points provide optimal locations for space exploration.

Five Lagrange points, known as L1 to L5, exist for any two orbital bodies, including the earth-sun system. L1, L2 & L3 are situated on the line through the centres of the two bodies, and are considered to be unstable points. L4 & L5 are the third vertices of the equilateral triangles that get formed with the centres of the two bodies, and are considered to be stable points. Each of these L-points has its own advantages. For instance, L1 provides an uninterrupted view of the sun, and the Solar & Heliospheric Observatory Satellite (SOHO) is currently placed there. Similarly, L2 provides a clear view of deep space, and is an ideal location for astronomical telescopes/observatories, such as the JWST and Planck.