Nu Cephei
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 45m 26.925s |
| Declination | +61° 07′ 14.90″ |
| Apparent magnitude (V) | 4.289 (4.25 - 4.35) |
| Characteristics | |
| Evolutionary stage | Blue supergiant |
| Spectral type | A2Iab |
| Apparent magnitude (U) | 4.94 |
| Apparent magnitude (B) | 4.81 |
| Apparent magnitude (J) | 3.14 |
| Apparent magnitude (K) | 2.85 |
| U−B color index | +0.119 |
| B−V color index | +0.518 |
| Variable type | Alpha Cygni |
| Astrometry | |
| Radial velocity (Rv) | −25.90 km/s |
| Proper motion (μ) | RA: −3.74 ± 0.13 mas/yr Dec.: −2.10 ± 0.12 mas/yr |
| Parallax (π) | 0.48±0.14 mas |
| Distance | 1,450 pc |
| Absolute magnitude (MV) | −6.82 |
| Details | |
| Mass | 15.4 M☉ |
| Radius | 137 R☉ |
| Luminosity | 102,000 L☉ |
| Surface gravity (log g) | 1.35 cgs |
| Temperature | 8,800 K |
| Rotational velocity (v sin i) | 15 km/s |
| Age | 8 Myr |
| Other designations | |
| 10 Cephei, HD 207260, HR 8334, SAO 19624, FK5 1572, BD+60°2288, HIP 107418 | |
| Database references | |
| SIMBAD | data |
Nu Cephei (ν Cephei) is a class A2, fourth-magnitude blue supergiant star in the constellation Cepheus, visible to the naked eye. It is a white pulsating α Cygni variable star located about 4,700 light-years from Earth.
ν Cephei is a member of the Cepheus OB2 stellar association, which includes stars such as μ Cephei and VV Cephei. It began life as an approximately 20 M☉ star around eight million years ago. It has now exhausted its core hydrogen and expanded and cooled into a supergiant. Elemental abundance analyses indicate that it has not yet spent time as a red supergiant, which would have brought about convection of fusion products to the surface in a Dredge-up.
ν Cephei is currently about 15 times as massive as the sun, 190 times as large, and 100,000 times as luminous. Its large size and luminosity cause it to be somewhat unstable and produce irregular pulsations. This is a common feature of class A and B supergiants, which are grouped as α Cygni variable stars. Variability was first reported by Helmut Abt in 1957. The brightness changes by at most a tenth of a magnitude. A variety of values for the variability period have been published, including 5 to 10 days, 7.6 days and 90 days.