VV Cephei

VV Cephei is a binary star system located in the constellation Cepheus. It consists of a red supergiant, VV Cephei A, which exceeds the Roche limit, if he his partner - comes closest - VV Cephei B, a blue giant. Then matter flow from it on his blue partners. The Blue Star seems to belong to the main sequence, he probably has already wrested much mass of VV Cephei A.


The first part of the name " VV " follows the rules for naming variable stars and states that VV Cephei is the fortieth variable star, which was discovered in the constellation Cepheus. The second part of the name " Cephei " is the genitive of the Latin name of the constellation Cepheus.

Physical Properties

VV Cephei A

The supergiant VV Cephei A is one of the largest known stars of the Milky Way. It belongs to the spectral class M2 and has approximately the 1,600 to 1,900 times the diameter of the sun. If he were in the place of our sun, then its largest expansion would even include the orbit of Saturn. Its brightness corresponds to about the 275,000 - to 575,000 times the luminosity of our Sun. The mass of the star is estimated by astronomers due to the movement of bodies located in its orbit at a mass of ~ 5 * 1031 to ~ 2 * 1032 kg, what the 25 - to 100-fold would be the sun. On the other hand, gives a statement based on its brightness between 25 and 40 solar masses.

VV Cephei B

VV Cephei B is a Blue Giant of the main sequence. He is a B star with ten times the solar diameter and 100,000 times the solar luminosity. One revolution of the system requires 7430 days ( 20.3 years ). His eclipse lasts about 1300 days in the middle of his last eclipse was in early January 1998.

Eclipsing binary star

The light curve shows almost no change, while VV Cephei B ( blue) passes in front of the supergiant VV Cephei A:

The light curve drops abruptly, however, when VV Cephei B passes behind VV Cephei A: