VV Cephei

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**VV Cephei**
Astrometry
Distance	~2,400^[1] ly
Absolute magnitude (M_V)	-9
Characteristics
Spectral type	M2 Iab
Details

Mass	25-40^[1] or 100 M_☉
Radius	1600-1900^[1] R_☉
Luminosity	275,000-575,000^[1] (bolometric) L_☉
Temperature	3300-3650^[1] K

Observation data Epoch J2000 Equinox J2000
Constellation	Cepheus
Right ascension	21h 56m 39.14s
Declination	+63° 37′ 32″
Apparent magnitude (V)	4.91^[1] (Naked eye)

VV Cephei is an eclipsing binary star system located in the constellation Cepheus, approximately 2,400 light years from Earth.^[1] A red hypergiant fills the system's Roche lobe when closest to its companion blue star, the latter appearing to be on the main sequence. Matter flows from the red hypergiant onto the blue companion.

[edit] VV Cephei A

The Sun compared with VV Cephei A

VV Cephei A compared with the Solar System

VV Cephei A, the hypergiant, is one of the largest stars known, and believed to be the second largest star in the Milky Way galaxy and third largest known after the hypergiant WOH G64 in the Large Magellanic Cloud. It is of spectral type M2 and is approximately 1,600–1,900 times the Sun's diameter, or approximately 2,436,875,000 km across. If placed in our solar system, the binary system would extend past the orbit of Jupiter and approach that of Saturn. VV Cephei is 275,000-575,000 times more luminous than the Sun. As is true for many red hypergiants, a stellar wind flows off the system at a velocity of approximately 25 kilometers per second.^[2] VV Cephei A's mass estimated from its orbital motion is about 100 solar masses, but its luminosity suggests a mass 25-40 solar masses. Consequently, the actual mass is unknown.

[edit] VV Cephei B

VV Cephei B, the blue main sequence star, is separated from the larger star by a distance of 25 AU on average, with the distance varying between 17 and 34 AU. It is a B0 star about 10 times the Sun's diameter and about 100,000 times its luminosity. The orbital period of the system is 7,430 days (20.3 years). The eclipse lasts about 1,300 days, and is total for about a year and a half. The midpoint of the last eclipse was in early January 1998.^[3]

[edit] See also

[edit] References

^ ^a ^b ^c ^d ^e ^f ^g Professor James B. (Jim) Kaler. "VV CEP (VV Cephei)". University of Illinois. http://www.astro.uiuc.edu/~kaler/sow/vvcep.html. Retrieved on 2009-07-12.
^ W. H. Bauer, P. D. Bennett, & A. Brown 2007 Astrophysical Journal Supplement Series 171, 249-259.
^ W. H. Bauer, P. D. Bennett, & A. Brown 2007. See especially their Figure 1, p. 250.