Why the Demon Star Winks Every Three Days

Algol sits in the constellation Perseus and answers to some of the best nicknames in the sky: the Demon Star, or the Ghoul. In Greek mythology, the star stands in for the blinking eye of the gorgon Medusa — a monster with a petrifying gaze, and, apparently, a habit of winking at us. NASA's October sky notes make the connection between the myth and the observation explicit in one word: blinking.