Nu Cephei
Nu Cephei (ν Cephei) is a class A2, fourth-magnitude supergiant star in the constellation Cepheus. It is a white pulsating α Cygni variable star located about 4,700 light-years from Earth.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 45m 26.925s[1] |
| Declination | +61° 07′ 14.90″[1] |
| Apparent magnitude (V) | 4.289[2] (4.25 - 4.35[3]) |
| Characteristics | |
| Spectral type | A2Iab[2] |
| Apparent magnitude (U) | 4.94[4] |
| Apparent magnitude (B) | 4.81[4] |
| Apparent magnitude (J) | 3.14[4] |
| Apparent magnitude (K) | 2.85[4] |
| U−B color index | +0.119[2] |
| B−V color index | +0.518[2] |
| Variable type | Alpha Cygni[3] |
| Astrometry | |
| Radial velocity (Rv) | −25.90[5] km/s |
| Proper motion (μ) | RA: −3.74 ± 0.13[1] mas/yr Dec.: −2.10 ± 0.12[1] mas/yr |
| Parallax (π) | 0.48 ± 0.14 mas[1] |
| Distance | 1,450[6] pc |
| Absolute magnitude (MV) | −6.82[7] |
| Details | |
| Mass | 15.4[6] M☉ |
| Radius | 137[6] R☉ |
| Luminosity | 102,000[6] L☉ |
| Surface gravity (log g) | 1.35[2] cgs |
| Temperature | 8,800[2] K |
| Rotational velocity (v sin i) | 15[2] km/s |
| Age | 8[8] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
ν Cephei is a member of the Cepheus OB2 stellar association,[8] which includes stars such as μ Cephei and VV Cephei.[9] It began life as an approximately 20 M☉[6][8] 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.[8]
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. The brightness changes by at most a tenth of a magnitude.[3]
References
- van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.Vizier catalog entry
- Firnstein, M.; Przybilla, N. (2012). "Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters". Astronomy & Astrophysics. 543: A80. arXiv:1207.0308. Bibcode:2012A&A...543A..80F. doi:10.1051/0004-6361/201219034. S2CID 54725386.
- Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
- Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
- Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
- Firnstein, Markus (2010). Quantitative Spectroscopy of Galactic BA-Type Supergiants (Ph.D.). Erlangen, Nürnberg, Univ.
- Verdugo, E.; Talavera, A.; Gómez De Castro, A. I. (1999). "Understanding A-type supergiants. II. Atmospheric parameters and rotational velocities of Galactic A-type supergiants". Astronomy and Astrophysics. 346: 819. Bibcode:1999A&A...346..819V.
- Yüce, Kutluay (2005). "Spectral Analysis of 4 Lacertae and ν Cephei". Baltic Astronomy. 14: 51. Bibcode:2005BaltA..14...51Y.
- Humphreys, R. M. (1978). "Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way". Astrophysical Journal. 38: 309. Bibcode:1978ApJS...38..309H. doi:10.1086/190559.
