HD 149026 b, formally named Smertrios /ˈsmɜːrtriɒs/, is an extrasolar planet approximately 250 light-years from the Sun in the constellation of Hercules. The 2.8766-day period planet orbits the yellow subgiant star HD 149026 at a distance of 0.042 AU (3.9 million mi; 6.3 million km) and is notable first as a transiting planet, and second for a small measured radius (relative to mass and incoming heat) that suggests an exceptionally large planetary core.