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Algol is the head of the demon, the star of evil. In Greek mythology Perseus beheaded the Medusa. At the location of the Medusa's head in the constellation of Perseus is Algol.
The system consists of a close pair of a blue star (A) and an orange giant (B) with a much further away yellow star (C).
Once star B was the biggest. But when it began to expand to become a red giant, a huge part of its former mass was absorbed by star A. 'Stellar cannibalsim'.
Algol A and B eclipse themselves with every revolution. This makes the star an eclipsing binary, the most famous of the breed.

Constellation: Perseus
Distance: 92.8 light-years
Radial velocity: 4 km/sec
Space between Algol A and B: 0.07 AU
Orbit period of Algol A and B: 2.86739 days
Orbit period of Algol A/B and C: 1.858 years

Algol A

Spectral class: B8
Visual magnitude: 2.31
Luminosity: 84 * Sun
Mass: 3.7 * Sun
Diameter: 2.94 * Sun

Algol B

Spectral class: K0
Visual magnitude: 5.79
Luminosity: 3.41 * Sun
Mass: 0.8 * Sun
Diameter: 3.2 * Sun

Algol C

Spectral class: F2
Visual magnitude: 5.59
Luminosity: 4.10 * Sun
Mass: 1.7 * Sun
Diameter: 1.5 * Sun

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Algol A, B and C
Astronomical Illustrations and Space Art, by Fahad Sulehria

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