| |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h33m 54.18821s[2] |
| Declination | +35° 15′ 03.02810″[2] |
| Apparent magnitude (V) | 4.61[3] (4.84 + 7.30)[4] |
| Characteristics | |
| Spectral type | K6: Ib + B2.5:[3] |
| B−V color index | 1.593±0.023[5] |
| Variable type | Lc[6] |
| Astrometry | |
| Radial velocity (Rv) | −4.6±0.3[7] km/s |
| Proper motion (μ) | RA: −3.746[2] mas/yr Dec.: −3.408[2] mas/yr |
| Parallax (π) | 0.7605 ± 0.2285 mas[2] |
| Distance | 4072+965 −773 ly (1249+296 −237 pc)[8] |
| Absolute magnitude (MV) | −4.1 (−4 + −1.5)[3] |
| Orbit[9] | |
| Period (P) | 1117±11 d |
| Eccentricity (e) | 0.00 (assumed) |
| Periastron epoch (T) | 2,447,088±10 JD |
| Semi-amplitude (K1) (primary) | 2.0±0.1 km/s |
| Details | |
| 47 Cyg Aa | |
| Mass | 12.1±0.2[10] M☉ |
| Radius | 601[11] R☉ |
| Surface gravity (log g) | 1.23[12] cgs |
| Temperature | 4,217[12] K |
| Metallicity [Fe/H] | 0.13[12] dex |
| Age | 17.6±0.6[10] Myr |
| 47 Cyg Ab | |
| Mass | 0.57[13] M☉ |
| 47 Cyg B | |
| Mass | 10.96[13] M☉ |
| Other designations | |
47 Cyg, V2125 Cyg, BD+34°4079, GC 28630, HD 196093/196094, HIP 101474, HR 7866, SAO 70203, WDS J20339+3515, 2MASS J20335419+3515031[14] | |
| Database references | |
| SIMBAD | data |
47 Cygni is a triple star[4][15] system in the northern constellationofCygnus, and is located around 4,000 light years from the Earth. It is visible to the naked eye with a combined apparent visual magnitude of 4.61.[3] The system is moving closer to the Earth with a heliocentric radial velocityof−4.6 km/s.[7]
The dual nature of this system was recognized by Annie Cannon in 1912, and she assigned the pair separate Henry Draper Catalogue identifiers.[9] They orbit each other with a period of around 143.69 yr.[13] The primary component is itself a spectroscopic binary in a near circular orbit with a period of around 3.06 yr. The a sin i value for the primary is 30.8 ± 1.6 Gm (0.206 ± 0.011 AU), where a is the semimajor axis and i is the orbital inclination. It has been repeatedly resolved by speckle interferometery since 1973. Radio emission was detected from this system in 1985/86.[9]
The supergiant primary is a slow irregular variable with an amplitude of about 0.1 magnitudes.[6] Its angular diameter has been measured at 4.472±0.017 milliarcseconds using interferometry by the Navy Precision Optical Interferometer.[16] At the distance of 1,249 parsecs,[8] it yield a radius of 601 R☉.[11] Its close companion has 57% of the mass of the Sun.[13] The secondary is a hot B-type main-sequence star, but still 2.5 magnitudes fainter than the primary.[4]
