A yellow hypergiant is a massive star with an extended atmosphere, a spectral class from late A to early K, an initial mass of as much as 20–50 solar masses, but having lost as much as half that mass. They are amongst the most visually luminous stars, with absolute magnitude (M_V) around -9, but also one of the rarest with just a handful known in the Milky Way. They are sometimes referred to as cool hypergiants in comparison to O- and B-type stars, and sometimes as warm hypergiants in comparison to red supergiants.