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Algol: The Demon Star

1-14-11 Perseus by Chandra X-ray Center
Algol, a.k.a., Beta, in the constellation Perseus. Credit: Chandra X-ray Center

In ancient times, certain sights in the sky were considered bad signs. For example, comets were thought of as portents of doom. One star that was considered "bad luck" for centuries is Algol, or Beta Persei.

Algol is the second brightest star in the constellation Perseus. Algol comes from the Arabic name for "ghoul" and Algol is sometimes called the Demon Star. Algol has a particularly creepy reputation in that it represents the part of the constellation that would be Medusa's severed head that Perseus holds in his hand.

Algol is a variable star that fluctuates in brightness from magnitude 2.1 to magnitude 3.4. Algol is actually a binary pair, with one star eclipsing the other every 2.867 days, with the actual drop in brightness lasting just a matter of hours. To catch Algol at minimum, first you have to find it and recognize what it looks like at maximum.

I like to refer to Perseus as the constellation that looks like an icicle, because it’s usually out in the winter and it makes a gently crooked path toward the ground. Look for Perseus in the northeast this weekend between the W shape of Cassiopeia and the V shape of Taurus. Its brightest star, Alpha Persei (Mirfak), is a part of the icicle shape (or, more traditionally, the form of Perseus). Beta Persei, or Algol, is to the right, as Perseus’ extended arm holds up Medusa's head.

Over the coming week, Algol will reach minimum brightness for about two hours during mideclipse centered at the following times:

January 15, 1:53 a.m. Central Time

January 17, 10:43 p.m. Central Time

January 20, 7:32 p.m. Central Time

January 23, 4:21 p.m. Central Time

See if you can spot the difference in Algol's brightness and maybe the "bad luck" star will be good luck for you!

-- Kelly Kizer Whitt loves clean, clear, and dark skies. Kelly studied English and Astronomy at the University of Wisconsin-Madison and worked for Astronomy magazine. She is currently the Feature Writer for Astronomy and Space at Suite101.com. You can follow her on Twitter at twitter.com/Astronomommy.

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