Analyses of the Ancient Chinese Report on the Total Solar Eclipse in 709 BCE: Implications for the Contemporaneous Earth’s Rotation Speed and Solar Cycles

Abstract Total solar eclipses have occasionally left their footprints on human history for millennia, serving as spot references for the Earth’s rotation speed and the solar cycle variations in the past. The earliest datable accounts with explicit mention date back to 709 BCE (hereafter −708) in ancient Chinese records, although the observational site and date were documented differently in previous studies. This study revisits the source reports and confirms the explicit mentions of the eclipse totality and a later addendum concerning the yellowish structure that has been traditionally associated with the K-corona “above and below” the eclipsed Sun. Archeological evidence allows us to revise the coordinate of Qūfù, the observational site, to N35°36′, E116°59′, in contrast to the previous studies. This location contradicts the recent Δ T spline curve, revising the Δ T constraint in −708 to 20,264 s ≤ Δ T ≤ 21,204 s and modifying other Δ T constraints from the eighth and sixth centuries BCE. The later addendum regarding the possible coronal structure requires a philological caveat on the source provenance, although it corroborates well with the recent solar cycle reconstruction. During the total solar eclipse, the solar disk was inclined at ≈58° from the local zenith at Qūfù, locating the possible coronal streamer belts at heliographic latitude ≈+32° ± 45° and −32° ± 45°. Our result broadly agrees with the inclination and width of the streamer belt reconstructed from the recent estimate of open solar flux based on radiocarbon data in the first millennium BCE and offers possible independent support for the recent solar cycle reconstruction in the late eighth century BCE.