Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Cygnus |
Right ascension | 20h 47m 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 | |
Database references | |
SIMBAD | data |
T Cygni is a binary star [9] system in the northern constellation of Cygnus. 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 shift of 8.4 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 separation of 8.10 ″ 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]