It’s about 300 years older than the previous record holder
The earliest documented case of an aurora dates to the early 10th century BCE. Ancient Chinese text describes ‘five-coloured light’ witnessed in the northern part of the night sky towards the end of the reign of King Zhao, the fourth king of the Chinese Zhou dynasty. The exact dates of Zhao’s reign aren’t known, but it’s likely that this event happened in either 977 or 957 BCE. Researchers discovered this colourful detail in the Bamboo Annals, a 4th-century BCE text written on bamboo slips that chronicled legendary and early Chinese history. Though scholars have been aware of the Bamboo Annals for some time, a fresh look at this particular section led to the realisation that it detailed what might be the earliest described aurorae, said study corresponding author Hisashi Hayakawa, an assistant professor at the Institute for Space-Earth Environmental Research at Nagoya University in Japan and a visiting scientist at the Rutherford Appleton Laboratory in the UK.
The newly analysed description likely refers to a geomagnetic storm, Hayakawa and study researcher Marinus Anthony van der Sluijs, an independent researcher based in Canada, reported in the study. Geomagnetic storms occur when the Sun – a‘breathing ball of gas’ – belches out solar flares, ginormous bubbles of electrified gas that travel at high speeds through space.
Earth’s magnetosphere usually protects the planet from the Sun’s energetic charged particles, but sometimes these particles get through and cause magnetic disturbances, known as geomagnetic storms. Such storms can produce beautiful lights – oxygen glows green and red, whereas nitrogen gives off blue and purple light. Nowadays, the northern lights, or aurora borealis, occur at northern latitudes, while the southern lights, or aurora australis, happen at southern latitudes. But during the mid-10th century, Earth’s north magnetic pole inclined towards the Eurasian continents – about 15 degrees closer to central China than it does today. As a result, it’s possible that ancient people in central China – possibly as far south as 40 degrees latitude, or just north of Beijing – could have seen geomagnetic storms and the colourful lights they produced.
Mid-latitude aurorae can present multiple colours when they’re bright enough, which could explain why the celestial event was noted as ‘five-coloured light’. For example, in October 1847, a colourful auroral display was observed in the UK, Hayakawa said. According to a report near Cambridge, “a crown was formed near the magnetic zenith from which all the rays appeared to diverge; their colours were most splendid and of pecu
