  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 21h 17m 55.08585s[1] |
| Declination | +34° 53′ 48.7255″[1] |
| Apparent magnitude (V) | 4.43[2] |
| Characteristics | |
| Spectral type | B2 Vne[3] |
| U−Bcolor index | −0.82[2] |
| B−Vcolor index | −0.11[2] |
| Astrometry | |
| Radial velocity (Rv) | −1.93±0.59[4] km/s |
| Proper motion (μ) | RA: +5.667[1]mas/yr Dec.: −5.601[1]mas/yr |
| Parallax (π) | 5.0120±0.1891 mas[1] |
| Distance | 650 ± 20 ly (200 ± 8 pc) |
| Absolute magnitude (MV) | −2.03[5] |
| Details | |
| Mass | 9.25±0.52[6] M☉ |
| Radius | 4.7[7] R☉ |
| Luminosity (bolometric) | 7,305[6] L☉ |
| Surface gravity (log g) | 3.30±0.10[8] cgs |
| Temperature | 22,000[6] K |
| Metallicity[Fe/H] | −0.36[5] dex |
| Rotational velocity (v sin i) | 230±24[4] km/s |
| Age | 17.0±2.8[9] Myr |
| Other designations | |
| υ Cyg,66 Cygni,BD+34°4371,FK5 1559,HD 202904,HIP 105138,HR 8146,SAO 71173[10] | |
| Database references | |
| SIMBAD | data |
Upsilon Cygni is astar in the northernconstellation ofCygnus. Its name is aBayer designation that isLatinized fromυ Cygni, and abbreviated Upsilon Cyg or υ Cyg. It is visible to the naked eye, having anapparent visual magnitude of 4.43. Based upon an annualparallax shift of5.0 mas, it lies at a distance of roughly 650 light years from theSun.
This is aB-type main sequence star with astellar classification of B2 Vne.[3] The 'e' suffix indicates this is aBe star, which means it is a rapidly rotating star surrounded by an orbiting gaseous disk. It has a highprojected rotational velocity of about 230 km/s,[4] which accounts for the nebulous appearance of its lines as indicated by the 'n' suffix. The emission region of its disk has a radius of0.20±0.04 AU.[7] The star itself is being viewed generally "pole-on", as ascertained by the lack ofabsorption features from the disk.[13]
Upsilon Cygni holds 9.3[6] times themass of the Sun and is 4.7[7] times theSun's radius. The rapid rotation is giving the star anoblate shape with anequatorial bulge that is 18% wider than the polar radius.[8] It is radiating 7,305[6] times thesolar luminosity from itsouter atmosphere at aneffective temperature of 22,000 K.[6]
The star shows variations in luminosity, including short term non-radial pulsations with periods of 2.95 and 2.6 per day, as well as random outbursts occurring up to every few years. The latter may be associated with mass-loss episodes. There is suspicion this is aspectroscopic binary, but no companion has been detected viaspeckle interferometry. Measured variations inradial velocity may be caused by a companion having anorbital period of about 11.4 years.[8] Several stars appear close to it in the sky, but they are likelyoptical companions.[14]