Topic: College of Sciences and Humanities

October 9, 2020

Charles W. Brown Planetarium

Across northern Europe 2,500 years ago, ancient Celtic tribes kept a close eye on the night skies in late October, watching for a star cluster called Pleiades to signal the beginning of winter.

When Pleiades was directly overhead at midnight, they knew it was time to celebrate a festival that included people dressing in costume and leaving food at their doorsteps to appease evil spirits, said Dayna Thompson, director of the Charles W. Brown Planetarium at Ball State.

Pieces of these practices ended up surviving until today, becoming trick-or-treating.

“The last day of October marked the harvest season and their end of summer, opening the door to a cold, dark winter,” she said. “On Halloween, or October 31, Celts would recognize this time with a festival called Samhain — meaning ‘summer’s end.’”

The public can learn about the holiday from Thompson and others in a 360-degree video experience, “Halloween: Celestial Origins,” available online.

Halloween is one of four cross-quarter days, which fall midway between the solstices and equinoxes. The others are February 2 (Groundhog Day), May 1 (May Day) and August 1.

Halloween falls roughly between the autumnal equinox and the winter solstice.

In the video, Thompson uses the planetarium projectors to analyze these aspects of Halloween and understand its origins. Viewers will be able to see the sky as it was 2,500 years ago.