Bob Moler's Ephemeris Blog

This is Ephemeris for Tuesday, October 29th. Today the Sun will be up for 10 hours and 17 minutes, setting at 6:34, and it will rise tomorrow at 8:18. The Moon, 3 days before new, will rise at 6:24 tomorrow morning.

Not all the ghosts and goblins out Thursday night will be children. One is out every night because it’s a star. Its name is Algol, from the Arabic for Ghoul or Demon Star. It’s normally the second-brightest star in the constellation Perseus the hero, visible in the northeast this evening. The star is located where artists have drawn the severed head of Medusa, whom he had slain. Medusa had snakes for hair so that she turned all who gazed upon her to stone. Algol is her still glittering eye. The star got this name before astronomers found out what was really wrong with it. They found out that it does a slow wink every two days, 21 hours, because it is two stars that eclipse each other. Her next 9-hour wink, is centered at 2 AM Halloween morning.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.

Addendum

Stellarium tends to show variable stars and a brightness about halfway between the brightest and dimmest magnitudes. However, Algol stays at its peak brightness most of the time, so it usually appears as bright as Mirfak which, in the image above, is to its upper left. It’s only during the eclipse that it appears dimmer than Mirfak. That’s how you can tell that Algol is in eclipse.

Here is where to go to find out when Algol is going to be in eclipse in the next week or so: http://www.astropical.space/algol.php