Beta Persei


Distance (Light Years) 93 ± 2
Apparent Magnitude 2.09
Color (B-V)-0.05

Names For This Star

The name derives from the Arabic name for this star: Ra's al Ghul, the Demon's Head. The Arabic ghul means a demon or mischief-maker. This Arabic noun is the origin of the English word "ghoul". A variant of the Arabic name is "El Ghoul."

Other names for the star are The Demon Star, Gorgona, "The Gorgon" or Gorgonea Prima, "The First Gorgon."

Description of the Star

Algol is a three star system containing an eclipsing binary pair. According to Burnham Algol is one of the most famous variable stars in the sky.

The primary, Algol A, is a blue B8V main sequence star. This spectral type implies that an effective temperature of 12000 K, a diameter 3 times that of the sun, and a luminosity about 170 times that of the sun and a mass of about 5 times that of the sun.

The secondary, Algol B, is a yellow G8IV subgiant that passes in front of Algol A every 2.86739 days producing a decrease in brightness of about 1.3 magnitudes. The entire eclipse lasts about 10 hours. Burnham estimates the distance between A and B at about 6 million miles. So the separation between the stars would be comparable to the their combined diameters.

The data given by Burnham for Algol B imply a luminosity about 1.5 times that of the sun. Algol B produces eclipses of the A component, because it is much less luminous than that star. The diameter of B would be about 3 million miles, making it in fact slightly larger than A in diameter.

Algol C was first detected by its effects on the orbit of the AB pair. C orbits with a period of 1.86 years. Burnham puts the radius of the orbit at about 0.5 AU. The spectral type of C is uncertain. It is however, certainly brighter than the sun and at least as massive.

Other Designations For This Star


26 Persei

Hipparcos Identifier (HIP Number)


Harvard Revised (HR Number)


Henry Draper Catalog (HD Number)


Bonner Durchmusterung (BD Number)

BD+40 673
Smithsonian Astrophysical
Observatory compendium (SAO Number)

Fundamental Katalog (FK5 Number)



Copyright © 1998 - 2010 by Arnold V. Lesikar,
Professor Emeritus
Dept. of Physics, Astronomy, and Engineering Science,
St. Cloud State University,St. Cloud, MN 56301-4498

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