Deneb
 Cygnus, the constellation in which Deneb is located. |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Cygnus |
| 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 Cyg |
| 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 ± 0.32mas |
| Distance | 802 ± 66pc |
| 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 |
Deneb (/ˈdɛnɛb/), also designated Alpha Cygni (α Cygni, abbreviated Alpha Cyg, α Cyg), is the brightest star in the constellation of Cygnus. It is one of the vertices of the asterism known as the Summer Triangle and forms the 'head' of the Northern Cross. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous stars. However, its exact distance (and hence luminosity) has been difficult to calculate; it is estimated to be somewhere between 55,000 and 196,000 times as luminous as the Sun.
α Cygni (Latinised to Alpha Cygni) is the star's Bayer designation. The traditional name Deneb is derived from dhaneb, Arabic for "tail", from the phrase ذنب الدجاجة Dhanab ad-Dajājah, or "tail of the hen". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Deneb for this star. It is now so entered in the IAU Catalog of Star Names.
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