1,400-Year-Old Mystery of Strange ‘Red Sign’ in Japan’s Sky Solved
It was likely an ethereal sky phenomenon.
By Meghan Bartels

A scarlet fan spread across the skies over Japan 1,400 years ago, and it’s been puzzling astronomers ever since.

According to historical records, on Dec. 30, 620, a “red sign” shaped like “a pheasant tail” appeared in the sky. At the time, the sign was considered a bad omen. Modern scientists looking back at the report have wondered whether the spectacle may have been caused by an aurora or a comet, but neither of those explanations quite made sense.

What might the “red sign” have looked like?
(Image: © Illustration: Space.com; Aurora: Nora Carol/Getty)

Ryuho Kataoka, who studies space weather at the National Institute of Polar Research in Japan, and his colleagues decided they wanted to investigate what could have caused the scarlet phenomenon, according to a statement.