Collisionless Periodic Orbits in the Free-Fall Three-Body Problem
The three-body problem considers the orbits of three masses under their mutual gravitational interactions. Periodic solutions are very hard to find and only a small set of solutions are known. A set of 316 families of collisionless periodic orbits in the free-fall three-body problem  are shown, labeled by . The orbits are shown in two-dimensional space and on a "shape sphere," based on Jacobi three-body coordinates. These can be divided into seven classes according to their geometric and algebraic symmetries. The red dots on the shape sphere are related to the three two-body collision points.
 X. Li and S. Liao, "More than Six Hundred New Families of Newtonian Periodic Planar Collisionless Three-Body Orbits," Science China Physics, Mechanics & Astronomy,60(12), 2017 129511. doi:10.1007/s11433-017-9078-5.
 M. Šuvakov and V. Dmitrašinović, "Three Classes of Newtonian Three-Body Planar Periodic Orbits," Physical Review Letters, 110(11), 2013 114301. doi:10.1103/PhysRevLett.110.114301.