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Red circle indicates location in Cepheus |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 56m 39.144s[1] |
| Declination | +63° 37′ 32.01″ |
| Apparent magnitude (V) | 4.91[2] (Naked eye) |
| Characteristics | |
| Spectral type | M2 Iab[3] / B8V |
| Astrometry | |
| Distance | 2,400 within 20 percent[2][foot 1] ly |
| Absolute magnitude (MV) | -9 |
| Details | |
| Mass | 25-40[2][foot 1] or 100 M☉ |
| Radius | 1600-1900[2][foot 1] R☉ |
| Luminosity | 275,000-575,000[2][foot 1] (bolometric) L☉ |
| Temperature | 3300-3650 or 3200[2] K |
| Other designations | |
VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus, approximately 2,400 light years from Earth.[2][foot 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. The red hypergiant, known as VV Cephei A, is currently recognised as the second largest star known, with an estimated solar radius between 1,600 and 1,900.[5][6] Like Betelgeuse, VV Cephei A is plagued by phenomena intrinsic to hypergiant stars that make them difficult to measure with precision. VV Cephei is not entirely spherical, and is surrounded by opaque shells of a highly extended atmosphere, which, coupled with limb darkening, unstable luminosity and other factors, make it difficult to determine its true size. It has a very small parallax, so estimates as to its distance, and consequently, most other deductions made about its nature, have a high margin of error.
Coordinates: 21h 56m 39.14s, +63° 37′ 32″
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