alf Ari is an orange K-type dwarf (about 1.50 solar masses, 4,553 K, 13.9 solar radii), 20.2 light-years from Earth. alf Ari b is a 1.80-Jupiter-mass companion, with an orbital period of 1.04 years, at 1.200 AU from its star, on an eccentric orbit (e ≈ 0.25), discovered in 2010 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.