Tau Cygni

light-years
Proper names: Tau Cygni, 65 Cygni
Catalog numbers:
     Gliese (Gl) 822.1, Henry Draper (HD) 202444, Bonner Durchmusterung (BD) +37°4240, Luyten Half-Second (LHS) 6, Hipparcos Input Catalog (HIC) 104887, Smithsonian Astrophysical Observatory (SAO) 71121, Aitken Double Star (ADS) 14787, Hoffleit Bright Star (HR) 8130, A.G. Clark (AGC) 13, Woolley (Wo) 9728
Arity: trinary
Right Ascension and Declination: 21h14m47.486s, +38°2'43.99" (epoch 2000.0)
Distance from Sol: 68.2 light-years (20.9 parsecs)
Standard error in distance: 1.2601%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 40.4, -35.5, 42.1
Galactic (X,Y,Z) coordinates in ly: 7.91, 67.2, -8.99
Proper motion: 0.465 arcsec/yr (20.0° from north)
Radial Velocity: -23.1 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -44.3, -15.4, 21.6

What do all these fields mean?

Data for A and B's orbit around one other:
Combined absolute visual magnitude: +2.12
Combined visual luminosity: 12.3 x Sol
Period: 49.8 years
Semimajor Axis: 17.8 A.U.s
Eccentricity: 0.24
Periastron distance: 13.5 A.U.s
Apastron distance: 22.1 A.U.s
Year in which periastron occurs: 1939.7
Source for orbit data: G. Van Biesbroeck
As seen from A:
     At periastron, B would appear as magnitude -21.10
     At apastron, B would appear as magnitude -20.04
As seen from B:
     At periastron, A would appear as magnitude -23.70
     At apastron, A would appear as magnitude -22.64

Data for (A-B) and C's orbit around one other:
Combined absolute visual magnitude: +2.12
Combined visual luminosity: 12.3 x Sol
Period: 45000 years
Observed Separation: 1841 A.U.s
Source for orbit data: Burnham's Celestial Handbook
As seen from (A-B):
     C would appear as magnitude -4.85
As seen from C:
     (A-B) would appear as magnitude -13.12


Component A:
Spectral class: F0
Luminosity Class: IV
Apparent visual magnitude: +3.82 (increasing to +3.72)
Absolute visual magnitude: +2.22 (increasing to +2.12)
Visual luminosity: 11.3 x Sol (increasing to 12.4 x Sol)
Variable type: delta Scuti (pulsating variable)
Color indices: B-V= +0.38, U-B= +0.03
Diameter: 3.60 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 3.36 A.U.s
Angular size of star in sky in CZ: 0.570449 degrees


Component B:
Spectral class: G0
Luminosity Class: V
Apparent visual magnitude: +6.42
Absolute visual magnitude: +4.82
Visual luminosity: 1.03 x Sol
Color indices: B-V= +0.60, U-B= +0.09
Diameter: 0.96 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 1.02 A.U.s
Angular size of star in sky in CZ: 0.504100 degrees


Component C:
Catalog numbers:
     Giclas (G) 211-14, Luyten (L) 1577-19
Right Ascension and Declination: 21h12m47s, +37°48'24" (epoch 1950.0)
Celestial (X,Y,Z) coordinates in ly: 40.2, -35.9, 41.8
Galactic (X,Y,Z) coordinates in ly: 8.44, 67.1, -8.85
Proper motion: 0.463 arcsec/yr (19.8° from north)
Radial Velocity: -23.1 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -44.3, -15.1, 21.3
Spectral class: M3
Luminosity Class: V
Apparent visual magnitude: +12.00
Absolute visual magnitude: +10.40
Visual luminosity: 0.0060 x Sol
Color indices: B-V= +1.53, U-B= +1.14, R-I= +1.04
Diameter: 0.46 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.078 A.U.s
Angular size of star in sky in CZ: 3.155426 degrees

light-years
but not more than light-years away
Data for this star system were most recently updated on 4-April-2001.