Y Cygni
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 52m 3.57718s |
| Declination | +34° 39′ 27.4861″ |
| Apparent magnitude (V) | 7.3 - 7.9 |
| Characteristics | |
| Primary | |
| Spectral type | O9.5V |
| Apparent magnitude (U) | 5.91 |
| Apparent magnitude (B) | 6.996 |
| Apparent magnitude (V) | 7.287 |
| U−B color index | −1.086 |
| B−V color index | −0.291 |
| Secondary | |
| Spectral type | O9.5V |
| Apparent magnitude (U) | 5.883 |
| Apparent magnitude (B) | 6.974 |
| Apparent magnitude (V) | 7.265 |
| U−B color index | −1.091 |
| B−V color index | −0.291 |
| Variable type | Algol |
| Astrometry | |
| Proper motion (μ) | RA: +2.763 mas/yr Dec.: −15.981 mas/yr |
| Parallax (π) | 0.6759±0.0338 mas |
| Distance | 4,900 ly (1,500 pc) |
| Absolute magnitude (MV) | −3.59/−3.62 |
| Absolute bolometric magnitude (Mbol) | −6.65±0.04/−6.7±0.04 |
| Orbit | |
| Primary | Y Cyg A |
| Companion | Y Cyg B |
| Period (P) | 2.99633210±0.00000031 d |
| Semi-major axis (a) | 28.72 R☉ |
| Eccentricity (e) | 0.14508 |
| Inclination (i) | 86.474±0.019° |
| Periastron epoch (T) | 2,446,308.66407±0.0001 |
| Argument of periastron (ω) (secondary) | 312.514° |
| Argument of periastron (ω) (primary) | 132.514±0.052° |
| Details | |
| Primary | |
| Mass | 17.72±0.35 M☉ |
| Radius | 5.785±0.091 R☉ |
| Luminosity | 36,000 L☉ |
| Surface gravity (log g) | 4.161±0.014 cgs |
| Temperature | 33,200±200 K |
| Rotational velocity (v sin i) | 132 km/s |
| Age | 2 Myr |
| Secondary | |
| Mass | 17.73±0.3 M☉ |
| Radius | 5.816±0.063 R☉ |
| Luminosity | 37,700 L☉ |
| Surface gravity (log g) | 4.157±0.01 cgs |
| Temperature | 33,521±40 K |
| Rotational velocity (v sin i) | 132 km/s |
| Age | 2 Myr |
| Other designations | |
| Y Cyg, HD 198846, HIP 102999 | |
| Database references | |
| SIMBAD | data |
Y Cygni is an eclipsing and double-lined spectroscopic binary star system in the constellation of Cygnus. It is located about 4,900 light-years from Earth. The system was one of the first binaries with a convincing detection of the apsidal precession.
The two stars, being O-type main-sequence stars, orbit each other with a period of nearly 3 days.