Mu Cephei, also known as Herschel's Garnet Star due to its red, garnet-like color, is a red hypergiant star in the Cepheus constellation. With a radius of 1,420 solar radii, or a diameter of 1,977,000,000 kilometers, it is one of the largest stars known. Mu Cephei is also the "prototype" of the semiregular variable star type.
- Emily M. Levesque1 et al 2005. "The effective temperature scale of galactic red supergiants: cool, but not as cool as we thought" Astrophysical Journal 628, 2.