61 Cygni

light-years
Proper names: 61 Cygni, The Flying Star
Catalog numbers:
     Gliese (Gl) 820, Smithsonian Astrophysical Observatory (SAO) 70919, Aitken Double Star (ADS) 14636, Fifth Fundamental Catalogue (FK5) 793, Struve (STF) 2758
Heavy element abundance: 80% of Sol
Standard error in heavy element abundance: 7%
Source for heavy element abundance: Strobel [Fe/H] Determinations
Arity: binary
Points of interest:
     Small systematic variations in the way these two stars orbit one another suggest that there is a third, unseen body orbiting 61 Cygni A, with a mass 8 times that of Jupiter (0.008 x Sol).  Its orbital period is 4.8 years, which would give it an average orbital distance of 2.4 A.U.s.  Despite its low mass, which is much too low for a star and is even on the low side for a brown dwarf, this third member has been dubbed "61 Cygni C."  Theoretical calculations suggest that its diameter is less than 0.1 x Sol.

Right Ascension and Declination: 21h6m54.592s, +38°44'44.99" (epoch 2000.0)
Distance from Sol: 11.43 light-years (3.504 parsecs)
Standard error in distance: 0.2516%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 6.489, -6.109, 7.152
Galactic (X,Y,Z) coordinates in ly: 1.438, 11.27, -1.188
Proper motion: 5.22 arcsec/yr (52.4° from north)
Radial Velocity: -64.8 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -93.10, -54.64, -7.914

What do all these fields mean?

Data for A and B's orbit around one other:
Combined absolute visual magnitude: +7.07
Combined visual luminosity: 0.129 x Sol
Period: 722 years
Semimajor Axis: 86.36 A.U.s
Eccentricity: 0.401
Periastron distance: 51.73 A.U.s
Apastron distance: 121.0 A.U.s
Year in which periastron occurs: 1689.7
Source for orbit data: F.J. Josties
As seen from A:
     At periastron, B would appear as magnitude -14.67
     At apastron, B would appear as magnitude -12.83
As seen from B:
     At periastron, A would appear as magnitude -15.53
     At apastron, A would appear as magnitude -13.68


Component A:
Catalog numbers:
     Henry Draper (HD) 201091, Bonner Durchmusterung (BD) +384343, Luyten Half-Second (LHS) 62, Hipparcos Input Catalog (HIC) 104214, Hoffleit Bright Star (HR) 8085, New Suspected Variable (NSV) 13543
Spectral class: K5
Luminosity Class: V
Apparent visual magnitude: +5.20
Absolute visual magnitude: +7.48
Visual luminosity: 0.0889 x Sol
Color indices: B-V= +1.18, U-B= +1.11, R-I= +0.47
Mass: 0.6 x Sol
Diameter: 1.051 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.298 A.U.s
Orbital period in CZ: 76.7804 days
Tidal index in CZ: 22.6297
Angular size of star in sky in CZ: 1.878248 degrees


Component B:
Catalog numbers:
     Henry Draper (HD) 201092, Bonner Durchmusterung (BD) +384344, Luyten Half-Second (LHS) 63, Hipparcos Input Catalog (HIC) 104217, Hoffleit Bright Star (HR) 8086, New Suspected Variable (NSV) 13546
Right Ascension and Declination: 21h6m55.31s, +38°44'31.4" (epoch 2000.0)
Celestial (X,Y,Z) coordinates in ly: 6.490, -6.109, 7.152
Galactic (X,Y,Z) coordinates in ly: 1.438, 11.27, -1.189
Proper motion: 5.22 arcsec/yr (52.4° from north)
Radial Velocity: -64.3 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -93.04, -54.14, -7.958
Spectral class: K7
Luminosity Class: V
Apparent visual magnitude: +6.05
Absolute visual magnitude: +8.33
Visual luminosity: 0.0405 x Sol
Color indices: B-V= +1.37, U-B= +1.23, R-I= +0.60
Mass: 0.5 x Sol
Diameter: 0.753 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.201 A.U.s
Orbital period in CZ: 46.5938 days
Tidal index in CZ: 61.4502
Angular size of star in sky in CZ: 1.996123 degrees

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