Rho Cassiopeiae

Rho Cassiopeiae ( /ˌroʊ kæsiəˈpiː.iː/; ρ Cas, ρ Cassiopeiae) is a yellow hypergiant star in the constellation Cassiopeia. It is about 8,200 light-years (2,500 pc) away from Earth, yet can still be seen by the naked eye (in the Northern Hemisphere only), as it is 500,000 times as luminous as the Sun. On average, it has an absolute magnitude of −9.5, making it one of the most luminous stars known. Its surface diameter measures 450 times that of the Sun, or approximately 630,000,000 kilometers. Being a yellow hypergiant, it is one of the rarest types of stars, one of only seven in the Milky Way that are currently known, though it is not the only one in its constellation, which also includes V509 Cassiopeiae. Rho Cassiopeiae is a single star, and is categorized as a semiregular variable.