Catch the "Demon Star" This Month

You'll have three chances in November to see this winking star.

Perseus and Caput Medusæ
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What could be more terrifying than a celestial entity dubbed the “Demon Star”? The fact that it’s called that because it looks like one of the snakes of Medusa is blinking right at you.

Statue of Perseus and Medusa
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For those not up on their Greek myths, Perseus was the hero who lopped off the head of the dreaded Gorgon monster who could turn you to stone with barely a side eye. And this lovely lady had a headful of snakes for hair. So that’s why in the Perseus constellation, there are stars named after the Gorgon (“Gorgonea”), and right next to them is the snakey eye of the Demon Star, whose true name is Algol (taken from the Arabic for “demon’s head”). The illustration above shows what the constellation would look like as a drawing.

The reason why it seems like the star is winking at you is because it’s actually made up of two stars orbiting each other. Every time the smaller one takes a spin around the larger one, it’s a star-on-star eclipse. So as the light dims and brightens, dims and brightens, it looks like Algol, the eye of the snake, is blinking or winking at you.

The other weird thing about Algol is how precise it is: The light dims like clockwork every two days, 20 hours, and 49 minutes. Exactly. Then it takes a few hours for it to brighten up again. Since this is the case, you’d think you would be able to see Algol all the time, but because of the Earth’s position to the sun, you can’t see it clearly except in November, and you only see it best when the moon is dark or at least, not very bright. See this handy star chart from NASA for where to look for it in the night sky.

Algol, the "Demon Star," can be seen in November 2019.
NASA/JPL-Caltech

This year, you have three opportunities to catch the demon: Nov. 9 at 3:17 a.m., Nov. 12 at 12:06 a.m., and Nov. 29 at just before 5 a.m. According to NASA's tips, you should start checking about an hour before the eclipse, so you can see it while it’s still bright before it dims. Binoculars or a telescope are best, but if the sky is clear and dark, you may even be able to see it with your own eyes. Good luck! And don’t get turned to stone.

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