Kapteyn is a cool M-dwarf (about 0.28 solar masses, 3,550 K, 0.29 solar radii), 3.9 light-years from Earth. Kapteyn c is a 7.0-Earth-mass planet, with an orbital period of 122 days, at 0.311 AU from its star, on an eccentric orbit (e ≈ 0.23), discovered in 2014 via radial velocity. The planet betrayed itself through the star's reflex motion — a technique that first revealed worlds around Sun-like stars in the 1990s and remains a workhorse of exoplanet discovery. The planet's marked eccentricity suggests past scattering events or perturbations from unseen companions.