A very luminous red supergiant, Mu Cephei is one of the largest stars visible to the naked eye, and in the entire Galaxy. It is best seen from the Northern hemisphere from August to January.
The star is approximately 1,650 times larger than our sun’s solar radius, and were it placed in the Sun’s position, its radius would reach between the orbits of Jupiter and Saturn. Mu Cephei could fit almost 4.5 billion suns into its volume. Only five known stars (VY Canis Majoris, KW Sagitarii, KY Cygni, V354 Cephei and VV Cephei) are believed to be larger than it. It is so large that it could fit 6.4 quadrillion Earths in it. If Earth were a golf ball (about 1.7 in/4.3 cm), Mu Cephei would be greater than the length of two Golden Gate Bridges laid end-to-end (about 3.4 mi./5.5 km).