10/31/2016 – Ephemeris – What’s a Halloween sky without the Ghoul Star

Ephemeris for Halloween, Monday, October 31st.  The Sun will rise at 8:20.  It’ll be up for 10 hours and 12 minutes, setting at 6:32.  The Moon, 1 day past new, will set at 7:28 this evening.

Not all the ghosts and goblins out tonight will be children.  One is out every night, because it’s a star.  Its name is Algol, from the Arabic for Ghoul Star or Demon Star.  The Chinese had a name for it that meant ‘piled up corpses’.  It’s the second brightest star in the constellation Perseus the hero, rising in the northeast this evening.  The star is located where artists have drawn the severed head of Medusa, whom he had slain.  Medusa was so ugly that she turned all who gazed upon her to stone.  Algol is her still glittering eye.  Astronomers finally found out what was wrong with Algol.  It does a slow 6 hour wink every 2 days 21 hours because it is two very close stars that eclipse each other in that period.  It did so this morning at 5:53 a.m.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

To run an app to calculate times for the minima of Algol click here:  http://www.skyandtelescope.com/observing/celestial-objects-to-watch/the-minima-of-algol/ courtesy of Sky and Telescope Magazine.

Perseus with Cassiopeia and Andromeda in the northeast at 8:30 p.m. on Halloween.  Created using Stellarium and GIMP.

Animation of an eclipsing binary star like Algol. Credit: Wikimedia Commons h/t Earth and Sky