The “Demon Star”, Algol 
Download FTS images for this lesson here.
Algol tuesday

Look at the three images, locate the obvious star near the middle of each image.  Compare that star in each image, from Tuesday to Wednesday to Thursday night.  Does the star look different from night to night?  How? 

If you load the FITS images, you can measure the brightness of the star by examining the “value” of the pixels that comprise the star (the star fills more than one pixel in the image).  With a program like AIP4WIN, you could actually calculate a Magnitude. 

Algol is called the “Demon Star” because it appears to brighten and dim in a regular cycle of 2.87 days.  You can verify this optically even with unaided eye.  The legend is that the star represented the winking eye of the Gorgon, a legendary monster.

Data such as at the AAVSO website actually indicates a secondary dimming, but not nearly as much as the main event.

As a scientist, can you come up with a model that might explain this data?

You see a tiny dim light far away, that regularly dims for a short period of time, then brightens again.  What could cause this?  Could you build a model that would appear to act this way, that would show an observer the periodic dimming?

After you come up with some models, take a look on the Web, there’s lots of information about Algol! 

Algol Wednesday
Algol Thursday