| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h47m 10.75239s[1] |
| Declination | +34° 22′ 26.8374″[1] |
| Apparent magnitude (V) | 4.93[2] + 10.03[3] |
| Characteristics | |
| Spectral type | K3 III[4] |
| B−V color index | 1.294±0.003[2] |
| Variable type | Lb:[5] |
| Astrometry | |
| Radial velocity (Rv) | −23.9±0.3[6] km/s |
| Proper motion (μ) | RA: +39.637[1] mas/yr Dec.: +8.068[1] mas/yr |
| Parallax (π) | 8.4327 ± 0.1348 mas[1] |
| Distance | 387 ± 6 ly (119 ± 2 pc) |
| Absolute magnitude (MV) | −0.74[2] |
| Details | |
| A | |
| Radius | 28.19+0.67 −0.86[1] R☉ |
| Luminosity | 241.4±4.5[1] L☉ |
| Surface gravity (log g) | 2.12[7] cgs |
| Temperature | 4,285+50 −67[1] K |
| Metallicity [Fe/H] | −0.12[7] dex |
| Other designations | |
T Cyg, BD+33° 4028, HD 198134, HIP 102571, HR 7956, SAO 70499, WDS J20472+3422A[8] | |
| Database references | |
| SIMBAD | data |
T Cygni is a binary star[9] system in the northern constellationofCygnus. It is a faint system but visible to the naked eye with a combined apparent visual magnitude of 4.93.[2] Based upon an annual Parallax shiftof8.4 mas,[1] it is located 387 light years away. It is moving closer to the Earth with a heliocentric radial velocity of −24 km/s.[6]
The primary, component A, is a variable star, most likely of the slow irregular type, which ranges in magnitude from 4.91 down to 4.96.[5] It is a giant star with a stellar classification of K3 III,[4] which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. The star has expanded to 28 times the radius of the Sun.[1] It is radiating 241 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,285 K.[1]
The secondary companion, component B, is a magnitude 10.03 star located at an angular separationof8.10″ along a position angle of 120°, as of 2012. In 1877 it was separated by 10.0″ with nearly the same position angle (121°).[3]
