Case file · Cosmic event
A 'black vapour' in the sun, 28 BCE
The Book of Han records that in 28 BCE the sun turned yellow and 'a black vapour as large as a coin' sat at its centre: a naked-eye sunspot, read at court as an omen.
28 BCE · 34.30, 108.88 · status: official
The account
Han astronomers in Chang'an treated marks on the sun as warnings about the emperor's conduct. Their long series of sunspot notes is now used to study the solar cycle before telescopes.