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10/31/2019 – Ephemeris – The perfect Halloween star

October 31, 2019

Ephemeris for Halloween, Thursday, October 31st. Today the Sun will be up for 10 hours and 14 minutes, setting at 6:33, and it will rise tomorrow at 8:20. The Moon, half way from new to first quarter, will set at 9:22 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. 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’s next nighttime minimum will be 1:46 a.m. on November 12th.

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


Algol Finder

Perseus, Cassiopeia, Andromeda with Algol finder animation for Autumn evenings. Created using Stellarium and GIMP.

Eclipsing Binary Star

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

Here is a web sit where you can calculate the minima of Algol and other eclipsing stars:  http://www.astropical.space/algol.php

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