81 Cet is a Sun-like G-type star (about 1.23 solar masses, 4,734 K, 11.2 solar radii), 101 light-years from Earth. 81 Cet b is a 3.31-Jupiter-mass companion, with an orbital period of 2.75 years, at 2.104 AU from its star, discovered in 2008 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. 81 Cet b circles in the outer system, comparable to the Jupiter region.