Astronomical Halloween

Pumpkin bin supermarket sentinels, cob web fluff, fold out spiders, broom stick witches. Pumpkin patch, amusement park Fright Night, haunted house tours, behemoth inflatable yard ghosts, pop-up fireworks outlets – it must be Halloween.

This year, take a moment to ponder astronomical Halloween, one of four “cross- quarter days” in a year – a cross-quarter day falls midway between a equinox (sun sets due west) and the solstice (sun sets at most northern or southern point on the horizon). March and September equinoxes, June and December solstices plus one cross-quarter between each, makes eight astronomical sub-divisions in a year.

Astronomical Halloween, rooted in the ancient Celtic festival Samhain took cues from the Pleiades star cluster. Cosmically vigilant pagans celebrated Samhain on the night Pleiades reached its highest point in the sky, coincidentally falling at cross-quarter time. Trouble is – the 7th century Catholic church knew nothing of Pleiades or cross-quarter days. They declared November 1 All Saints Day (honoring any saints who didn’t have their own day), October 31 All Hallows Eve (mass for all who are hallowed) – set in stone dates based on a wonky Julian calendar.

Had the Gregorian calendar been applied, Halloween would fall on November 7.

A color-composite image of the Pleiades from the Digitized Sky Survey. Image credit: NASA/ESA/AURA/Caltech

A color-composite image of the Pleiades from the Digitized Sky Survey. Image via NASA/ESA/AURA/Caltech.

3 thoughts on “Astronomical Halloween

  1. You probably see more Halloween parties than I do — regardless of the day it occurs.
    As little as I know/understand about things astronomical I continue to be amazed by it in my own simple way. Hard to realize how big the universe is and how disporportionately large we think we humans are….

  2. Hard for me to say how much I dislike the commercial hijacking of this day, and how I detest the church hijacking of the original festival as a sop to the pagans. But I didn’t know about the Pleiades association, so your day has not been in vain.

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