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VV Cephei

binary star in the constellation Cepheus

Key facts

Constellation: Cepheus
Right ascension: 21 56 39.14385
Declination: +63 ° 37 ′ 32.0174 ″
Apparent magnitude v: 4.91 (4.80 - 5.36 )
U b color index: +0.43
B v color index: +1.73
Variable type: EA + SRc
Evolutionary stage: Red supergiant
Spectral type: M2 Iab (M1p 0)

via Wikipedia infobox

Article

VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus. It is both a B[e] star and shell star. As a 5th magnitude star, it is visible to the naked eye under good observing conditions.

VV Cephei is an eclipsing binary with the third longest known period. 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 supergiant primary, known as VV Cephei A, is currently recognised as one of the largest stars in the galaxy although its size is not certain. Estimates range from 660 R☉ to over 1,000 R☉.