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Moon and Spica

May 25, 2018

A star with an important history huddles close to the Moon tonight. Spica, the leading light of Virgo, is to the lower right of the Moon at nightfall. It’s one of the brighter stars in the sky, and it’s not close to any other bright stars, so it stands out.

Many cultures have used Spica as a calendar marker. Partly that was because of its brightness and isolation. But it was also because the times of year at which it appeared and disappeared coincided with important agricultural events. And that connection led to its name — Spica means a “spike” or ear of grain.

A study a few years ago suggested that Spica guided wheat farming in the Fertile Crescent — the area of the Middle East where wheat was first domesticated.

The study said that, more than 10,000 years ago, Spica disappeared in the west just after sunset when it was time to harvest the wheat crop. And it returned to view in the east just before sunrise almost six weeks later, when it was time to thresh the grain. It was the only star that could have served as a calendar marker for both events.

Another study looked at a calendar of ancient Armenia. It found that the year began with Spica’s first appearance in the dawn sky, a few days before the summer solstice. That places the birth of the calendar at about the same time that agriculture was beginning in the region.

Spica has played a role in many other cultures as well — helping them track the changing seasons.

Script by Damond Benningfield

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