Case file · Cosmic event
The 'red sign' like a pheasant's tail
The Nihon Shoki records that on 30 December 620 a red sign shaped like a pheasant's tail appeared in the sky, Japan's oldest dated record of a sky phenomenon.
620 CE · 34.47, 135.82 · status: disputed
The account
In 2020 Ryuho Kataoka and Kazuaki Yamamoto argued it was a fan-shaped red aurora. Japan's magnetic latitude was higher in the 7th century (about 33 degrees against about 25 today), so strong auroras were more likely to be seen from the Asuka court.
The sceptical view
Auroras are usually streaky rather than fan-shaped, and a comet has also been proposed; the identification is a plausible reading, not a certainty.