Algol Variables
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Basic Information

Algol Variables, or Algol-type binaries are a specific type of eclipsing binaries. It's a pair of stars, one brighter than the other, that eclipse one another when viewed from earth, and appear as a single variable star to the naked eye. When neither star is in eclipse, they appear as a single bright star. When the hotter star passes behind the cooler one, the star seems to get dimmer. When the hotter star passes in front of the cooler one, they appear dimmer than normal as well, but not as dim as when the hotter star is hidden. (So when viewed from earth, they have basically three different levels of brightness. People living in the system itself would experience them as just a normal binary stars, not variable at all.)

Unlike beta Lyrae variables and W Ursae Majoris variables, Algol variables retain the usual spherical star shape, and are not so close as to be deformed by each other's gravity.

Over 3,000 Algol star pairs have been documented and identified in the sky, but the category is named for the famous "Demon Star" Algol.



Game and Story Use

  • An ancient or primitive culture might come up with extensive mythology to explain why an Algol Variable Star in the heavens has an oscillating vibrancy.
    • They may have holy days or other observances that are keyed to the stars' patterns of brightening and dimming.
    • Perhaps the myths tell a tale of divine brothers locked in eternal struggle, with the brightness depending on who has the upper hand. Generations later, when science develops enough to understand what's really causing the stellar variability, it looks kinda suspicious that the ancient primitives understood there were two stars (two brothers = two stars). This is seen as proof of ancient astronaut theories, not mere coincidence.
    • Or maybe the stars are thought of as dancing to the music of Azathoth or some other eldritch abomination. Algol is the "the demon star", so a blinking/dimming star might have similar negative connotations in your setting.
  • Depending on how FTL technology works in your setting, the lined-up eclipsing nature of the variable pair might have some impact on navigation or space travel.
    • It probably also depends a bit on how fast the two stars orbit each other, as it's possible they move so quickly as to be a dangerous navigational hazard you don't want to approach.
    • Or maybe the intense gravity or magnetic waves put off from the pair of dancing stars can be used as an interstellar slingshot or navigational beacon.
  • What appears at first to be an Algol Variable pair turns out instead to be an inhabited system with advanced technology. The dimming effect that was previously thought to be caused by eclipsing stars is actually caused by a stellar megastructure sometimes blocking the view. This is likely determined by a new space telescope getting higher resolution images than ever before, but it could also be revealed in a more dramatic fashion, such as a broadcast or visible action from the megastructure's builders.
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