Stellar classification



  • X -46
  • Y -23
  • Z -77
→ Sol: 93

Object type

  • Eclipsing binary of Algol type
  • Star
  • Double or multiple star
  • Infra-Red source
  • Spectroscopic binary
  • UV-emission source
  • Variable Star
  • X-ray source
simbad:* bet Per


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. It is the first and best known eclipsing binary, and one of the first non-nova variable stars to be discovered. It is a three-star system, consisting of Beta Persei Aa1, Aa2, and Ab - in which the large and bright primary β Persei Aa1 is regularly eclipsed by the dimmer β Persei Aa2. Thus, Algol's magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every 2.86 days (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.

This article uses material from the Wikipedia article "Algol", which is released under the Creative Commons Attribution-Share-Alike License 3.0.