Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cygnus |
Right ascension | 21h 14m 47.4916s |
Declination | +38° 02′ 43.141″ |
Apparent magnitude (V) | 3.65 - 3.75[1] (3.80 / 6.69[2]) |
Characteristics | |
Spectral type | F2 IV + G0 V |
U−B color index | +0.03 / +0.09 |
B−V color index | +0.38 / +0.60 |
Variable type | δ Sct[1] |
Astrometry | |
Radial velocity (Rv) | -21.1 km/s |
Proper motion (μ) | RA: 195.75 mas/yr Dec.: 410.03 mas/yr |
Parallax (π) | 47.80 ± 0.61 mas |
Distance | 68.2 ± 0.9 ly (20.9 ± 0.3 pc) |
Orbit[3] | |
Period (P) | 49.5240 years |
Semi-major axis (a) | 0.92224 arcseconds |
Eccentricity (e) | 0.24535 |
Inclination (i) | 133.242 degrees° |
Longitude of the node (Ω) | 161.343 degrees° |
Periastron epoch (T) | 1938.5919 |
Argument of periastron (ω) (secondary) | 116.416 degrees° |
Details | |
τ Cyg A | |
Mass | 1.65[2] M☉ |
Radius | 2.48[2] R☉ |
Surface gravity (log g) | 3.87[2] cgs |
Temperature | 6,600[2] K |
Metallicity [Fe/H] | 0.05[2] dex |
τ Cyg B | |
Mass | 1.03[2] M☉ |
Radius | 0.93[2] R☉ |
Surface gravity (log g) | 4.52[2] cgs |
Temperature | 5,670[2] K |
Other designations | |
Database references | |
SIMBAD | data |
A | |
B |
Tau Cygni, Latinised from τ Cygni, is a binary star system in the constellation Cygnus, approximately 69 light years away from Earth.[4] This visual binary system has a period of 49.6 years.[2]
The main star, 4th magnitude GJ 822.1 A, is a yellowish white subgiant star of the spectral type F2IV. It therefore has a surface temperature of 6,000 to 7,500 kelvins and is larger, hotter, and several times as bright as the Sun.[5] Its companion, 6th magnitude GJ 822.1 B, is a yellow main sequence star of the spectral type G0V. It is similar to the Sun in size, surface temperature, and luminosity.[6]
Tau Cygni is classified as a δ Scuti variable. The magnitude range is given as 3.65 to 3.75, which is the combined magnitude for both components, although the variable component is A.[1]
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