Deneb
| 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 | |
| Evolutionary stage | Blue supergiant |
| 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) | 2.31±0.32 mas |
| Distance | 1,410±196 or 2,615±215 ly (433±60 or 802±66 pc) |
| Absolute magnitude (MV) | −8.38 |
| Details | |
| Mass | 15.5±0.8 or 19±4 M☉ |
| Radius | 117+14 −19 or 203±17 R☉ |
| Luminosity | 55,100±10,000 or 196,000±32,000 L☉ |
| Surface gravity (log g) | 1.10±0.05 – 1.45 cgs |
| Temperature | 8,700±150 K |
| Metallicity [Fe/H] | −0.25 dex |
| Rotational velocity (v sin i) | 20±2 km/s |
| Age | 11.6±0.5 Myr |
| Other designations | |
| Arided, Aridif, Gallina, Arrioph, α Cygni, 50 Cygni, BD+44°3541, FK5 777, HD 197345, HIP 102098, HR 7924, SAO 49941 | |
| Database references | |
| SIMBAD | data |
Deneb (/ˈdɛnɛb/) is a blue supergiant star in the constellation of Cygnus. It is the brightest star in the constellation and the 19th brightest in the night sky, with an apparent magnitude slightly varying between +1.21 and +1.29. Deneb is one of the vertices of the asterism known as the Summer Triangle and the "head" of the Northern Cross. Its Bayer designation is α Cygni, which is Latinised to Alpha Cygni, abbreviated to Alpha Cyg or α Cyg.
Deneb rivals Rigel, a closer blue supergiant, as the most luminous first-magnitude star. However, its distance, and hence luminosity, is poorly known; its luminosity is estimated to be between 55,000 and 196,000 times that of the Sun. Distance estimates range from 1,400 to 2,600 light-years; assuming its highest value, it is the farthest star with an apparent magnitude brighter than 2.50.