HD 13931 is a Sun-like G-type star (about 1.30 solar masses, 5,867 K, 1.25 solar radii), 47.4 light-years from Earth. HD 13931 b is a 2.20-Jupiter-mass companion, with an orbital period of 11.5 years, at 5.150 AU from its star, discovered in 2009 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. HD 13931 b circles in the outer system, comparable to the Jupiter region.