Proxima Centauri
Radial velocity measurements made in 2017 were precise enough to show that Proxima Centauri and Alpha Centauri AB are gravitationally bound. The orbital period of Proxima Centauri is approximately years, with an eccentricity of 0.50 ± 0.08, much more eccentric than Mercury's. Proxima Centauri comes within of AB at periastron, and its apastron occurs at .