HD 99109 is a Sun-like G-type star (about 0.76 solar masses, 5,282 K, 0.98 solar radii), 54.8 light-years from Earth. HD 99109 b is a 0.44-Jupiter-mass companion, with an orbital period of 1.20 years, at 1.110 AU from its star, on an eccentric orbit (e ≈ 0.09), discovered in 2005 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 99109 b orbits at roughly the distance of Mars from the Sun.