Delta Cygni
Delta Cygni (δ Cygni, abbreviated Delta Cyg, δ Cyg) is a binary star of a combined third-magnitude in the constellation of Cygnus. It is also part of the Northern Cross asterism whose brightest star is Deneb. Based upon parallax measurements obtained during the Hipparcos mission, Delta Cygni is located roughly 165 light-years (51 parsecs) distant from the Sun.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 44m 58.47854s |
| Declination | +45° 07′ 50.9161″ |
| Apparent magnitude (V) | 2.87 |
| Characteristics | |
| Spectral type | A0 IV (B9 III + F1 V) |
| U−B color index | –0.10 |
| B−V color index | –0.02 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | –20.1 km/s |
| Proper motion (μ) | RA: +44.07 mas/yr Dec.: +48.66 mas/yr |
| Parallax (π) | 19.77 ± 0.48 mas |
| Distance | 165 ± 4 ly (51 ± 1 pc) |
| Absolute magnitude (MV) | −0.74 |
| Orbit | |
| Primary | A |
| Companion | B |
| Period (P) | 780.27 yr |
| Semi-major axis (a) | 3.0″ |
| Eccentricity (e) | 0.4670 |
| Details | |
| Mass | 2.93 M☉ |
| Radius | 5.13 R☉ |
| Luminosity | 155 L☉ |
| Surface gravity (log g) | 3.49 cgs |
| Temperature | 10,150 K |
| Rotational velocity (v sin i) | 135 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta Cygni's two components are designated Delta Cygni A (officially named Fawaris /fəˈwɛərɪs/) and B. More widely separated is a faint third component, a 12th magnitude star that is moving along with the others. Together they form a triple star system.
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