57 Cygni
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 53m 14.75503s |
| Declination | +44° 23′ 14.1408″ |
| Apparent magnitude (V) | 4.80 |
| Characteristics | |
| Spectral type | B5 V |
| B−V color index | −0.134±0.006 |
| Astrometry | |
| Radial velocity (Rv) | −21.1±2.8 km/s |
| Proper motion (μ) | RA: +11.94 mas/yr Dec.: −2.08 mas/yr |
| Parallax (π) | 6.21±0.22 mas |
| Distance | 530 ± 20 ly (161 ± 6 pc) |
| Absolute magnitude (MV) | −1.23 |
| Orbit | |
| Period (P) | 2.8548 days |
| Eccentricity (e) | 0.139±0.014 |
| Inclination (i) | ≈ 48° |
| Periastron epoch (T) | 2441571.275 JD |
| Argument of periastron (ω) (secondary) | 159.6° |
| Semi-amplitude (K1) (primary) | 111.9 km/s |
| Semi-amplitude (K2) (secondary) | 126.0 km/s |
| Details | |
| 57 Cyg A | |
| Mass | 5.54±0.55 M☉ |
| Radius | 3.3±0.4 R☉ |
| Temperature | 17,190 K |
| Rotational velocity (v sin i) | 40 km/s |
| 57 Cyg B | |
| Mass | 4.92±0.49 M☉ |
| Radius | 2.9±0.4 R☉ |
| Rotational velocity (v sin i) | 30 km/s |
| Other designations | |
| 57 Cyg, BD+43°3755, HD 199081, HIP 103089, HR 8001, SAO 50180 | |
| Database references | |
| SIMBAD | data |
57 Cygni is a close binary star system in the constellation Cygnus, located about 530 light years from Earth. It is visible to the naked eye as a blue-white hued star with a baseline apparent visual magnitude of 4.80. The pair have a magnitude difference of 0.34. This system is moving closer to the Earth with a heliocentric radial velocity of −21 km/s.
This is a double-lined spectroscopic binary with an orbital period of 2.85 days and an eccentricity of 0.15. They show a steady change in their longitude of periastron, showing an apsidal period of 203±4 years. The system does not form an eclipsing binary, having the orbital inclination of around 48°. Both components are B-type main-sequence stars with a stellar classification of B5 V.