Halloween festivities are in full swing here in Indy. Pumpkin patches, corn mazes and haunted houses are on everybody’s minds. But, did you know that Halloween is actually an astronomical holiday? In fact, the timing of present day Halloween is based on the calendar of ancient cultures like the Celts and Druids. It is believed that theses cultures divided each year into four major seasons, marked by quarter days. These seasons were then divided with a cross-quarter day, marking the natural procession of the seasons. But these days weren’t set arbitrarily. They relied on the sky to set their calendars.

The Charles W. Brown Planetarium will host “Halloween Astronomy” on select Friday and Saturday nights through the month of October, where guests age 8 and up can learn how Halloween fits in as a “cross-quarter day.”