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Algol (HD 19356)

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Description

Algol known colloquially as the Demon Star, is a bright star in the constellation Perseus. It is one of the best known eclipsing binaries, the first such star to be discovered, and also one of the first (non-nova) variable stars to be discovered. Algol is actually a three-star system (Beta Persei A, B, and C) in which the large and bright primary Beta Persei A is regularly eclipsed by the dimmer Beta Persei B. Thus, Algol’s magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every 2 days, 20 hours and 49 minutes during the roughly 10-hour long partial eclipses. There is also a secondary eclipse (the “second minimum”) when the brighter star occults the fainter secondary. This secondary eclipse can only be detected photoelectrically. Algol gives its name to its class of eclipsing variable, known as Algol variables.

Name
Algol
Common name
Beta Persei
Constellation
Perseus
Apparent visual magnitude
2.12
Type
Eclipsing binary of Algol type
RA
03 08 10.13245
DEC
+40 57 20.3280
Distance (LY)
24,000 - 33,900
More info
Check in Wikipedia