Discerning the demon star's dip in brightness

Jan 26

Written by:
1/26/2015 7:24 PM  RssIcon

Algol is an interesting star name; it comes from the Arabic "ra's al-ghūl" that literally means "head of the ogre, or ghoul." While the evidence of our ancient ancestors having seen the variable nature of this star is lacking, it would behighly coincidental then that this star is also where Perseus is said to be holding the decapitated head of the Gorgon Medusa. Algol magnitude dip and brightenShe was the snake-headed beast that could turn living creatures to stone that were unfortunate enough to gaze upon her face.

And the star is a "winking" one; while the other stars in the heavens would have largely appeared of constant brightness, Algol may have been known to dip in brightness. Today, we know that period is 2 days, 20 hours and 49 minutes. 

Because of this, the star is not always ideally placed overhead for many of us to see either during the dip down, or the rise back up. But this week offers a unique opportunity: On the evening of January 27, Algol will be in the process of dimming from it's brighter 2.1 magnitude, and reach minimum brightness at the following time:

  • 10:42 pm EST
  • 9:42 pm CST
  • 8:42 pm MST
  • 7:42 pm PST

So for the eastern part of the United States, viewing Algol in the process of dimming should be easy as Perseus begins to become visible after sunset. Keep checking on the star every 30 to 60 minutes or so, checking it around the time of minimum. For west coast observers, it may be easier to start at minimum, and watch as it rises towards maximum brightness. 


Where to find Algol in the night sky


And not to forget our European friends, Algol displays the same "dip in brightness dance" again more conveniently on January 30. Just after midnight January 30th, into the morning of January 31 at 12:30 am, Algol dips to minimum for UTC/GMT time zones. This makes it ideal to watch from brightest to dimmest. For the Americas, look for the star to be at minimum early in the evening, and watch it rise out of that towards brightest magnitude. The time of minimum for that across the USA time zones are:

  • 7:31 pm EST
  • 6:31 pm CST
  • 5:31 pm MST
  • 4:31 pm PST

Mountain and Pacific viewers will have to settle for the best view they can get as soon as Algol comes into view, and watch it continue rising towards maximum. 

Either way, give it a try this week - learn where to find Algol in the sky here.


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The Nightlight

This blog includes what to see in the night and daytime skies, thoughts on telescopes, binoculars, and other astronomy observing accessories and equipment, plus my own occasional notes on objects I've seen and observed. Oh, and the random theater or other "my take on life" post. In other words, there is always something interesting. Check it out.