Algol

Also known as Beta Persei, 26 Persei

Algol , designated Beta Persei (β Persei, abbreviated Beta Per, β Per), known colloquially as the Demon Star, is a bright multiple star in the constellation of Perseus and one of the first non-nova variable stars to be discovered.

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Algol is a bright star in the constellation Perseus, also known as the "Demon Star," that consists of multiple stars orbiting together. It is historically significant because it was one of the earliest variable stars discovered—stars whose brightness visibly changes over time—making it important in the development of astronomy.

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Wikidata facts

Distance from Earth: 93
Diameter: 5750000
Image: Algol AB movie imaged with the CHARA interferometer - labeled.gif

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Commons category: Algol
catalog code: UBV M 9337
spectral class: B8
parallax: 36.27
absolute magnitude: -0.15
color index: -0.37
radial velocity: 4.0
Commons gallery: Algol
apparent magnitude: 2.08
stellar rotational velocity: 67
right ascension: 47.04221855625
declination: 40.95564667028
effective temperature: 12445
right ascension component of proper motion: 11
declination component of proper motion: -28
age estimated by a dating method: 570

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Article

12 sections

Contents

Observation history
System
Names
The official name Algol
Ghost and demon star
First star of Medusa's head
Chinese names
Observing Algol
Cultural significance
See also
References
External links

Algol is a three-star system, consisting of Beta Persei Aa1, Aa2, and Ab – in which the hot luminous primary β Persei Aa1 and the larger, but cooler and fainter, β Persei Aa2 regularly pass in front of each other, causing eclipses. Thus Algol's magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every 2.86 days during the roughly 10-hour-long partial eclipses. The secondary eclipse when the brighter primary star occults the fainter secondary is very shallow and can only be detected photoelectrically.