alf Tau is an orange K-type dwarf (about 1.13 solar masses, 4,055 K, 45.1 solar radii), 20.4 light-years from Earth. alf Tau b is a 6.47-Jupiter-mass companion, with an orbital period of 1.72 years, at 1.460 AU from its star, on an eccentric orbit (e ≈ 0.10), discovered in 2015 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. alf Tau b orbits at roughly the distance of Mars from the Sun.