A red supergiant fills its Roche lobe when closest to a companion blue star, the latter appearing to be on the main sequence.

Matter flows from the red supergiant onto the blue companion for at least part of the orbit and the hot star is obscured by a large disk of material.

The fact that VV Cephei is an eclipsing binary system was discovered by American astronomer Dean McLaughlin in 1936.

[25] The spectrum of VV Cep can be resolved into two main components, originating from a cool supergiant and a hot small star surrounded by a disk.

[20] Forbidden lines, mainly of FeII but also of CuII and NiII, are mostly constant in radial velocity and during eclipses, so they are thought to originate in distant circumbinary material.

[26] The spectrum varies dramatically during the primary eclipses, particularly at the ultraviolet wavelengths produced most strongly by the hot companion and its disc.

During ingress and egress, the emission line profiles change as one side or the other of the disc close to the star becomes visible while the other is still eclipsed.

Rapid random variations in the short wavelength (i.e. hot) continuum appear to arise from the disc around the B component.

Shell absorption lines show variable radial velocities, possibly due to variations in accretion from the disk.

The spectroscopic radial velocities showing the secondary with equal mass to the primary is explained as being of a portion of the disc rather than the star itself.

VV Cephei A is fairly clearly identified as an M2 supergiant, and as such, it is given a temperature around 3,800 K. The secondary star is heavily obscured by a disk of material from the primary, and its spectrum is almost undetectable against the disc emission.

Detection of some ultraviolet absorption lines narrow down the spectral type to early B and it is apparently a main-sequence star, but likely to be abnormal in several respects due to mass transfer from the supergiant.