An eclipsing binary with a composite spectrum, in which the components are a late-type bright giant or supergiant and an early-type star. Immediately before and after primary eclipse the hot star is visible through the outermost layers of the secondary. If the spectrum shows features which indicate the presence of an M-type supergiant, emission, or mass transfer (but not necessarily eclipses), the star is sometimes known as a VV Cephei star. In Zeta Aurigae and VV Cephei themselves the orbital periods are 972 and 7430 days, respectively. The secondary in VV Cep is estimated to have a diameter over 1000 times that of the Sun, making it one of the largest stars known.
Subjects: Astronomy and Astrophysics.