Algol

light-years
Proper names: Algol, The Demon Star, Beta Persei, 26 Persei
Catalog numbers:
     Henry Draper (HD) 19356, Bonner Durchmusterung (BD) +40°673, Aitken Double Star (ADS) 2362, Hoffleit Bright Star (HR) 936, Smithsonian Astrophysical Observatory (SAO) 38592, Fifth Fundamental Catalogue (FK5) 111, Caltech 2-microns Survey (IRC) +40055, Hipparcos Input Catalog (HIC) 14576, Woolley (Wo) 9110
Arity: trinary
Points of interest:
     Algol A and B are close enough together to be a mass-exchange binary, where one star deposits material onto the other. Algol A probably used to be less massive, while Algol B probably used to be more massive. Probably, Algol B swelled up into its red giant phase at the end of its main-sequence lifetime, and in the process its surface got close enough to Algol A for Algol A's gravity to pull material off of it.

Right Ascension and Declination: 3h8m10.131s, +40°57'20.43" (epoch 2000.0)
Distance from Sol: 92.8 light-years (28.5 parsecs)
Standard error in distance: 2.4972%
Source for distance: Hipparcos
Celestial (X,Y,Z) coordinates in ly: 47.8, 51.3, 60.8
Galactic (X,Y,Z) coordinates in ly: -77.4, 45.7, -23.1
Proper motion: 0.0041 arcsec/yr (104.0° from north)
Radial Velocity: 4 km/sec
Source for proper motion and radial velocity: Hipparcos Input Catalog
Galactic (U,V,W) velocity components in km/s: -3.64, 1.54, -0.83

What do all these fields mean?

Data for A and B's orbit around one other:
Combined absolute visual magnitude: -0.00
Combined visual luminosity: 87.4 x Sol
Period: 2.86739 days
Semimajor Axis: 0.07 A.U.s
Eccentricity: 0.033
Periastron distance: 0.06769 A.U.s
Apastron distance: 0.07231 A.U.s
Source for orbit data: Burnham's Celestial Handbook
Comfort Zone (visual) around both: 9.35 A.U.s
As seen from A:
     At periastron, B would appear as magnitude -33.90
     At apastron, B would appear as magnitude -33.76
As seen from B:
     At periastron, A would appear as magnitude -37.38
     At apastron, A would appear as magnitude -37.24

Data for (A-B) and C's orbit around one other:
Combined absolute visual magnitude: -0.05
Combined visual luminosity: 91.5 x Sol
Period: 1.858 years
Semimajor Axis: 0.31 A.U.s
Eccentricity: 0.2
Periastron distance: 0.25 A.U.s
Apastron distance: 0.38 A.U.s
Year in which periastron occurs: 1903.6
Source for orbit data: P.J. Bachmann, J.L. Hershey
Comfort Zone (visual) around both: 9.57 A.U.s
As seen from (A-B):
     At periastron, C would appear as magnitude -31.26
     At apastron, C would appear as magnitude -30.38
As seen from C:
     At periastron, (A-B) would appear as magnitude -34.58
     At apastron, (A-B) would appear as magnitude -33.70

Data for (A-B) and C's orbit, take 2:
Period: 1.862 years
Semimajor Axis: 2.96 A.U.s
Eccentricity: 0.23
Periastron distance: 2.28 A.U.s
Apastron distance: 3.64 A.U.s
Year in which periastron occurs: 1952.05
Source for orbit data: A. Labeyrie et al.
As seen from (A-B):
     At periastron, C would appear as magnitude -26.46
     At apastron, C would appear as magnitude -25.45
As seen from C:
     At periastron, (A-B) would appear as magnitude -29.79
     At apastron, (A-B) would appear as magnitude -28.77


Component A:
Spectral class: B8
Luminosity Class: V
Apparent visual magnitude: +2.31
Absolute visual magnitude: +0.04
Visual luminosity: 84.0 x Sol
Variable type: Algol (eclipsing binary)
Period of variability: 2.86739 days
Color indices: B-V= -0.09
Mass: 3.7 x Sol
Source for mass: Burnham's Celestial Handbook
Diameter: 2.94 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 9.17 A.U.s
Orbital period in CZ: 14.43 years
Tidal index in CZ: 0.004802
Angular size of star in sky in CZ: 0.170745 degrees


Component B:
Spectral class: K0
Luminosity Class: III-IV
Apparent visual magnitude: +5.79
Absolute visual magnitude: +3.52
Visual luminosity: 3.41 x Sol
Variable type: Algol (eclipsing binary)
Mass: 0.8 x Sol
Source for mass: Burnham's Celestial Handbook
Diameter: 3.2 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 1.85 A.U.s
Orbital period in CZ: 2.80396 years
Tidal index in CZ: 0.127191
Angular size of star in sky in CZ: 0.924179 degrees


Component C:
Spectral class: F2
Luminosity Class: V
Apparent visual magnitude: +5.59
Absolute visual magnitude: +3.32
Visual luminosity: 4.10 x Sol
Mass: 1.7 x Sol
Source for mass: Burnham's Celestial Handbook
Diameter: 1.5 x Sol
Source for diameter: Burnham's Celestial Handbook
Comfort Zone (visual): 2.02 A.U.s
Orbital period in CZ: 2.20849 years
Tidal index in CZ: 0.205026
Angular size of star in sky in CZ: 0.395090 degrees

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