1,400-year-old mystery of strange 'red sign' in Japan's sky solved

[Judi Lynn]

By Meghan Bartels - Space.com Senior Writer 3 days ago

It was likely an ethereal sky phenomenon.



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

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.

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.

They began by comparing the historical description with a modern understanding of auroras. Although these celestial dances are often green, they can appear in other colors, including red, depending on which elements in Earth's atmosphere are being activated by charged particles spit out by the sun.

More:
https://www.livescience.com/japan-sky-lights-mystery-red-aurora.html