Another star found in the constellation Cepheus that is among the largest and most luminous stars in the Milky Way is Mu Cephei. It is a so-called red supergiant star and may be the largest star visible to the naked eye, and possibly, in the whole galaxy.
Visually, Mu Cephei emits about 100,000 times more light than the Sun does. It takes a billion suns to match the size of Mu Cephei.
It is also known as Herschel’s Garnet Star, as its deep red color was noted by William Herschel (1738-1822), a German-born British astronomer. This star is currently unstable in terms of light output, temperature, and size. It is, moreover, believed to be nearing death.