Capella and Capella H

Proper names: Capella, Alpha Aurigae, 13 Aurigae, Capella and Capella H, The Goat Star
Catalog numbers:
     Gliese (Gl) 194, Henry Draper (HD) 34029, Bonner Durchmusterung (BD) +45°1077, Hipparcos Input Catalog (HIC) 24608, Smithsonian Astrophysical Observatory (SAO) 40186, Aitken Double Star (ADS) 3841, Fifth Fundamental Catalogue (FK5) 193, Hoffleit Bright Star (HR) 1708, New Suspected Variable (NSV) 1897
Arity: quarternary (!)
Points of interest:
     The dimmer pair of this four-star star system is usually referred to as “Capella H”, because the C, D, E, F, and G letter designations were wasted on nearby stars that looked like they might be gravitationally bound to Capella A or B but in fact were not.
     Note that the comfort zones for either of Capella A or B are farther out than the orbital distance between these two stars. However, a planet could orbit the Capella A-B pair far enough out for the two stars to act as a single gravitational source and near enough for it to receive enough energy to sustain life.

Right Ascension and Declination: 5h16m41.353s, +45°59'52.9" (epoch 2000.0)
Distance from Sol: 42.2 light-years (12.9 parsecs)
Standard error in distance: 1.1384%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 5.51, 28.8, 30.4
Galactic (X,Y,Z) coordinates in ly: -40.2, 12.3, 3.77
Proper motion: 0.431 arcsec/yr (169.2° from north)
Radial Velocity: 22.2 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -29.1, -16.3, -8.77

What do all these fields mean?

Data for A and B's orbit around one other:
Combined absolute visual magnitude: -0.48
Combined visual luminosity: 136 x Sol
Period: 104.096 days
Semimajor Axis: 0.71 A.U.s
Eccentricity: 0
Periastron distance: 0.71 A.U.s
Apastron distance: 0.71 A.U.s
Year in which periastron occurs: 1936.46
Source for orbit data: H.A. McAlister
Comfort Zone (visual) around both: 11.7 A.U.s
As seen from A:
     At periastron, B would appear as magnitude -31.91
     At apastron, B would appear as magnitude -31.91
As seen from B:
     At periastron, A would appear as magnitude -32.16
     At apastron, A would appear as magnitude -32.16

Data for Ha and Hb's orbit around one other:
Combined absolute visual magnitude: +9.60
Combined visual luminosity: 0.013 x Sol
Period: 388 years
Semimajor Axis: 48.1 A.U.s
Eccentricity: 0
Periastron distance: 48.1 A.U.s
Apastron distance: 48.1 A.U.s
Year in which periastron occurs: 2010
Source for orbit data: W.D. Heintz
As seen from Ha:
     At periastron, Hb would appear as magnitude -10.02
     At apastron, Hb would appear as magnitude -10.02
As seen from Hb:
     At periastron, Ha would appear as magnitude -13.52
     At apastron, Ha would appear as magnitude -13.52

Data for (A-B) and (Ha-Hb)'s orbit around one other:
Combined absolute visual magnitude: -0.48
Combined visual luminosity: 136 x Sol
Observed Separation: 11000 A.U.s
Source for orbit data: Burnham's Celestial Handbook
As seen from (A-B):
(Ha-Hb) would appear as magnitude -1.77
As seen from (Ha-Hb):
(A-B) would appear as magnitude -11.85

Component A:
Spectral class: G5
Luminosity Class: III
Apparent visual magnitude: +0.71
Absolute visual magnitude: +0.15
Visual luminosity: 75.8 x Sol
Mass: 3 x Sol
Diameter: 10.8 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 8.71 A.U.s
Orbital period in CZ: 14.8363 years
Tidal index in CZ: 0.004543
Angular size of star in sky in CZ: 0.658898 degrees

Component B:
Proper motion: 0.431 arcsec/yr (169.2° from north)
Radial Velocity: 33.9 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -40.3, -12.9, -7.73
Spectral class: G0
Luminosity Class: III
Apparent visual magnitude: +0.96
Absolute visual magnitude: +0.40
Visual luminosity: 60.2 x Sol
Mass: 2.8 x Sol
Diameter: 7.45 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 7.76 A.U.s
Orbital period in CZ: 12.9212 years
Tidal index in CZ: 0.005990
Angular size of star in sky in CZ: 0.511970 degrees

Component Ha:
Proper names: Capella H
Catalog numbers:
Gliese (Gl) 195, Catalogue Astrographique (AC) +45°217-363, Giclas (G) 96-29
Right Ascension and Declination: 5h13m42s, +45°47'30" (epoch 1950.0)
Celestial (X,Y,Z) coordinates in ly: 5.90, 28.8, 30.2
Galactic (X,Y,Z) coordinates in ly: -40.2, 12.4, 3.37
Proper motion: 0.415 arcsec/yr (170.3° from north)
Radial Velocity: 31.2 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -37.3, -12.4, -8.53
Spectral class: M2
Luminosity Class: V
Apparent visual magnitude: +10.20
Absolute visual magnitude: +9.64
Visual luminosity: 0.012 x Sol
Mass: 0.3 x Sol
Diameter: 0.56 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.11 A.U.s
Orbital period in CZ: 24.3655 days
Tidal index in CZ: 224.714
Angular size of star in sky in CZ: 2.711288 degrees

Component Hb:
Proper names: Capella H
Catalog numbers:
Gliese (Gl) 195, Catalogue Astrographique (AC) +45°217-363, Giclas (G) 96-29
Right Ascension and Declination: 5h13m42s, +45°47'30" (epoch 1950.0)
Celestial (X,Y,Z) coordinates in ly: 5.90, 28.8, 30.2
Galactic (X,Y,Z) coordinates in ly: -40.2, 12.4, 3.37
Proper motion: 0.415 arcsec/yr (170.3° from north)
Radial Velocity: 31.2 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -37.3, -12.4, -8.53
Spectral class: M4
Luminosity Class: V-VI
Apparent visual magnitude: +13.70
Absolute visual magnitude: +13.14
Visual luminosity: 0.00048 x Sol
Mass: 0.1 x Sol
Diameter: 0.25 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.022 A.U.s
Orbital period in CZ: 3.76083 days
Tidal index in CZ: 9432.2
Angular size of star in sky in CZ: 6.066832 degrees

Data for this star system were most recently updated on 4-April-2001.