Deneb
Deneb (/ˈdɛnɛb/) is a first-magnitude star in the constellation of Cygnus. Deneb is one of the vertices of the asterism known as the Summer Triangle and the "head" of the Northern Cross. It is the brightest star in Cygnus and the 19th brightest star in the night sky, with an average apparent magnitude of +1.25. A blue-white supergiant, Deneb rivals Rigel as the most luminous first-magnitude star. However, its distance, and hence luminosity, is poorly known; its luminosity is somewhere between 55,000 and 196,000 times that of the Sun. Its Bayer designation is α Cygni, which is Latinised to Alpha Cygni, abbreviated to Alpha Cyg or α Cyg.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Pronunciation | /ˈdɛnɛb/, /ˈdɛnəb/ |
| Right ascension | 20h 41m 25.9s |
| Declination | +45° 16′ 49″ |
| Apparent magnitude (V) | 1.25 (1.21–1.29) |
| Characteristics | |
| Spectral type | A2 Ia |
| U−B color index | −0.23 |
| B−V color index | +0.09 |
| Variable type | Alpha Cygni |
| Astrometry | |
| Radial velocity (Rv) | −4.5 km/s |
| Proper motion (μ) | RA: 1.99 mas/yr Dec.: 1.95 mas/yr |
| Parallax (π) | 2.29 ± 0.32 mas |
| Distance | 2,615±215 ly (802±66 pc) |
| Absolute magnitude (MV) | −8.38 |
| Details | |
| Mass | 19±4 M☉ |
| Radius | 203±17 R☉ |
| Luminosity | 196,000±32,000 L☉ |
| Surface gravity (log g) | 1.10±0.05 cgs |
| Temperature | 8,525±75 K |
| Metallicity [Fe/H] | −0.25 dex |
| Rotational velocity (v sin i) | 20±2 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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