A 2025 study reconciled the Chūnqiū record of a total solar eclipse at Qufu by revising both the ancient city’s location and the ΔT constraint used in the eclipse calculation. The researchers identify the eclipse as July 17, 709 BCE, and place the Lu-period city about 8 km from coordinates used in earlier studies. Their paper was published on December 2, 2025.
The eclipse recorded at Qufu
The Chūnqiū, a chronicle of the state of Lu, says the Sun was totally eclipsed on the first day of the seventh month, on the rénchén day. The modern date of July 17, 709 BCE is the researchers’ astronomical identification of that calendar entry. In astronomical year numbering, the year is −708.
Why the historical location matters
Archaeological reports and historical geography led the researchers to place the Lu-period city at 35°36′ N, 116°59′ E. That location is about 8 km from the coordinates used in earlier studies. Eclipse visibility depends on the observer’s position, so identifying the ancient capital more accurately changes where calculations place the Moon’s shadow.
How the revised calculation reaches totality
The location revision is one part of the explanation. The calculation also depends on ΔT, the time offset between a theoretical uniform timescale and time measured from Earth’s rotation. The researchers used JPL DE 441 ephemeris data and the Sôma method to derive a revised ΔT constraint for 709 BCE of 20,264–21,204 seconds. This is a model constraint, not a count of how many seconds shorter an ancient day was.
An earlier estimate of about 20,170 seconds produced a modeled maximum eclipse magnitude of 0.994 at Qufu, short of totality. With the revised historical location and the revised ΔT constraint, the researchers’ calculation places Qufu within the modeled path of totality.
| Calculation | ΔT for 709 BCE | Modeled result at Qufu |
| Earlier estimate discussed in the study | About 20,170 seconds | Maximum eclipse magnitude of 0.994, short of totality |
| Revised calculation | 20,264–21,204 seconds | Qufu lies within the modeled path of totality |
The same analysis gives Qufu-based ΔT constraints of 21,150–21,968 seconds for an eclipse in 600 BCE and 16,379–21,574 seconds for one in 548 BCE. The researchers note a calendar-text problem affecting the 600 BCE record.
Stickstory’s English-language explainer places the Qufu correction alongside broader discussion of Earth’s rotation, including tides, fossil corals and timekeeping.
What the later Hànshū passage says
A much later passage in the Hànshū describes the eclipsed Sun as “completely yellow above and below.” The researchers say the text’s earlier provenance is unknown, so it cannot be established as an eyewitness account of the 709 BCE eclipse. Its possible interpretation as a description of the solar corona, the Sun’s outer atmosphere, remains conditional.
